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Review

Recent Developments in Hydrogen Production, Storage, and Transportation: Challenges, Opportunities, and Perspectives

by
Sanjay Kumar Singh Patel
1,2,3,
Rahul K. Gupta
1,
M. V. Rohit
2 and
Jung-Kul Lee
1,*
1
Department of Chemical Engineering, Konkuk University, Seoul 05029, Republic of Korea
2
Bioconversion Technology Division, Sardar Patel Renewable Energy Research Institute, Anand 388120, Gujarat, India
3
Department of Biotechnology, Hemvati Nandan Bahuguna Garhwal University (A Central University), Srinagar 246174, Uttarakhand, India
*
Author to whom correspondence should be addressed.
Fire 2024, 7(7), 233; https://doi.org/10.3390/fire7070233
Submission received: 4 May 2024 / Revised: 25 June 2024 / Accepted: 1 July 2024 / Published: 3 July 2024
(This article belongs to the Special Issue Hydrogen Safety: Challenges and Opportunities)
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Abstract

:
Hydrogen (H2) is considered a suitable substitute for conventional energy sources because it is abundant and environmentally friendly. However, the widespread adoption of H2 as an energy source poses several challenges in H2 production, storage, safety, and transportation. Recent efforts to address these challenges have focused on improving the efficiency and cost-effectiveness of H2 production methods, developing advanced storage technologies to ensure safe handling and transportation of H2, and implementing comprehensive safety protocols. Furthermore, efforts are being made to integrate H2 into the existing energy infrastructure and explore new opportunities for its application in various sectors such as transportation, industry, and residential applications. Overall, recent developments in H2 production, storage, safety, and transportation have opened new avenues for the widespread adoption of H2 as a clean and sustainable energy source. This review highlights potential solutions to overcome the challenges associated with H2 production, storage, safety, and transportation. Additionally, it discusses opportunities to achieve a carbon-neutral society and reduce the dependence on fossil fuels.

1. Introduction

Large-scale use of renewable energy is a vital strategy for reducing fossil energy consumption and achieving ‘net zero’ emissions by 2050. Green hydrogen (H2) is a promising technology that utilizes renewable energy sources [1]. H2 may be produced through several processes, each with its own advantages and limitations. Standard methods of H2 production include water (H2O) electrolysis, steam methane (CH4) reforming, biomass gasification, and biological processes [2,3]. The H2O electrolysis process uses an electric current to split H2O molecules into H2 and oxygen (O2) [4]. The steam CH4 reforming process involves the heating of a natural gas and steam mixture to produce H2 and carbon dioxide (CO2) [5,6]. Biomass gasification converts organic materials such as agricultural waste or wood chips into a mixture of H2, CO2, and other gases through a thermochemical process [7,8]. Each method carries a different implication for carbon emission and sustainability. Additionally, emerging technologies such as photoelectrochemical electrolysis and algae-based biological H2 production are promising alternatives for green H2 production [9,10]. Thus, the development of efficient and sustainable methods for H2 production by combining biological and non-biological procedures such as electrocatalytic and photocatalytic H2O splitting is crucial for meeting the increasing global demand for energy and reducing reliance on fossil fuels [11,12].
Moreover, different types of H2 production need to be considered based on the extraction methods [13]. Gray H2 is produced through carbon-intensive processes such as coal or natural gas gasification; blue H2 is created by combining natural gas or coal gasification with carbon capture technologies to reduce carbon emissions; green H2 is produced through H2O electrolysis using renewable energy sources [13,14,15]. Gasification is one of the most prominent thermochemical technologies for converting biomass into renewable fuels and chemicals. It converts biomass into a mixture of gases, including H2, carbon monoxide (CO), and CH4, which may be used as energy sources [16,17]. H2O electrolysis is one of the approaches to produce low-carbon H2, which can generate lower emissions when compared to fossil-based or direct grid electrification [18]. Projections from the International Energy Agency indicate that 3.3 trillion worldwide installations for H2O electrolysis technologies with a capacity of 15,000 TWh of electricity are required to achieve net zero emissions by 2050 [19]. The electrolysis process involves splitting H2O into H2 and O2 with the help of electricity. Electrolyzers can be large-scale central production facilities directly connected to renewable energy systems or other non-greenhouse-gas-emitting forms of electricity production, or they can be small-sized devices ideal for small-scale hydrogen production [20]. The three types of electrolyzers commonly used for commercial scale operations are alkaline, proton exchange membrane (PEM), and solid oxide electrolyzer cell (SOEC). The significant difference between these three types of electrolyzers is that they are separators and electrolytes, with working temperatures of 700–800 °C for SOEC and 70–100 °C for PEM and alkaline fuel cells [19,21,22]. Based on production capacity and efficiency, commercial alkaline electrolyzer systems can have efficiencies between 43 and 69%. The cost of these systems can vary from 600 to 2600 €/kW, with most estimations being around 1100 €/kW [19]. Future alkaline electrolyzers are expected to require capital expenditures of 400–900 €/kW. Compared to PEM and SOEC, the primary benefits of alkaline electrolyzers are their low capital costs, huge plant sizes, and long life spans [19,23]. The cost of H2 produced by electrolysis (green H2) is comparatively high at $4/kg over $1.2/kg for fossil fuels (grey H2) [24]. Soon, it can be expected that costs linked to electrolyzers and solar electricity will decline, and fossil fuel reforming costs associated with raw materials will be enhanced to favor electrolysis. Other important considerations include the transport and distribution of H2, for which various H2 production, storage, and application methods have been explored to meet the demands of an H2-based economy [25,26]. H2 storage is a crucial aspect of successfully implementing H2 technology. The various H2 storage techniques that have been explored include compressed gas storage, liquid H2 storage, and solid-state storage [27,28]. Each storage method has different advantages and limitations in terms of efficiency, safety, and cost. Compressed gas storage involves compressing H2 gas at high pressure into storage tanks [29,30]. Liquid H2 storage involves liquifying H2 by cooling it to extremely low temperatures for storage in cryogenic tanks [31,32]. Solid-state storage includes adsorptive storage on high-surface-area adsorbents, chemical storage in metals and complex hydrides, and storage in boranes [33,34]. Furthermore, H2 storage technology has advanced to include reversible storage options and hydrolytic release of H2 with off-board regeneration, which are solutions for potentially efficient and sustainable H2 storage [35,36]. However, none of the existing storage methods fully satisfy the requirements of an H2-based economy [37,38,39]. Therefore, ongoing research and development efforts are focused on improving the efficiency, safety, and cost-effectiveness of H2 production and storage technologies [29,40]. This review discusses the detailed processes associated with H2 production, storage, and transportation and presents the related recent updates, challenges, and perspectives.

2. Hydrogen Production

H2 production is crucial for achieving a sustainable low-carbon future, and it requires the implementation of advanced methods and technologies [41]. Figure 1 illustrates the various H2 production methods.

2.1. Thermochemical Routes

Thermal processes use energy from various resources such as biomass, coal, and natural gas to produce H2. Alternatively, the heat associated with closed chemical cycles helps produce H2 from H2O (feedstock) [42]. Thermochemical processes such as biomass gasification, biomass-derived liquid reforming, natural gas reforming (steam CH4 reforming; SMR), and solar thermochemical H2 (STCH) have been used to produce H2 [6,43]. The H2 production by SMR process reached up to 74% in the industrial sector [44]. In recent years, biomass gasification has gained significant attention as an energy production process. In this process, biomass materials such as agricultural waste or wood chips are converted into a combustible gas mixture known as syngas (CO + H2) [45]. Syngas is used as fuel for power generation or other industrial processes. Biomass gasification significantly reduces greenhouse gas (GHG) emissions compared with that of fossil fuel-based energy production [16,46]. Recently, the improvement in H2 production through biomass gasification has been proposed via (i) minimizing tar/car formations using KCl as a catalyst, (ii) altering the temperature to enhance syngas composition, and (iii) enhancement in H2 efficiency from up to 80% through capturing CO2 using calcium oxide [44]. To achieve the zero-waste strategy, the thermally decomposed spent LiNixCoyMn1−x−yO2 batteries-derived novel Ni/Co/Mn-loaded mesoporous Al2O3 catalyst exhibited significantly higher H2 productivity 151% from a temperature of 600 to 800 °C using pinewood sawdust and polyethylene co-gasification over control catalysts (17.2 mmol/g) [47]. Additionally, developing advanced gasification technologies and integrating biomass gasification with other renewable energy sources such as solar or wind power may further enhance the efficiency and viability of biomass gasification [16,48]. Biomass gasification may also be used to manage waste by converting organic waste into valuable energy. Furthermore, integrating biomass gasification with carbon capture and storage technologies would potentially result in negative emissions. This makes gasification a useful tool for combating climate change [42]. The multi-source heat and power system, biomass gasification, solar collecting, SOEC, steam power, and gas turbine integrated systems achieved an energy efficiency of 64.5% and a feasible levelized cost of electricity of $0.16/kWh [8].
The liquids obtained from biomass (ethanol, bio-oils, and other liquid biofuels) could be used to generate H2 via a reforming process [13,49]. Compared with biomass, these liquids are easy to transport over long distances for H2 production and distribution at fueling centers. This is a three-step process: (i) liquid fuels react with steam at high temperatures in the presence of catalysts to generate reformate gas (H2, CO, and CO2); (ii) extra H2 and CO2 are generated from the reaction of CO and steam at high temperatures through an H2O–gas shift reaction; and (iii) H2 separation and purification [13,50]. The steam reforming of biomass-derived levulinic acid using 15Ni/NiAl2O4 catalysts at 800 °C exhibited high carbon conversion, H2 yield, and concentration of 96.3, 92.8, and 67.9%, respectively [51]. This type of process is a mid-term technology because large-scale biomass-based liquids can be produced at facilities near the sources (biomass feedstocks), which is economical as it reduces the cost of H2 transportation to reforming sites [50]. However, the problematic reforming of larger molecules (more carbon atoms in liquid fuels than in natural gas (CH4)) and the need for efficient catalysts to enhance selectivity and yield are a few major challenges associated with this process. Moreover, future studies are needed to identify ways to reduce the costs associated with biomass-based liquids, equipment, operation, and maintenance and enhance overall process efficiency [43,49,50].
Natural gas reforming gasification converts natural gas into synthetic gas [6]. This process is commonly used for producing H2, ammonia, and methanol. To produce 10 tons of liquid H2/day, the steam CH4 reforming H2 liquefaction and waste heat recovery system established on liquified cold natural gas showed specific energy consumption, coefficient of performance, and exergy efficiency of 5.93 kWh/kg of liquid H2, 0.22% and 53.24% under optimum conditions, respectively [52]. The challenges associated with the natural gas reforming gasification process include high energy consumption, the need for catalysts, and the management of CO2 emissions [13,48]. Despite these challenges, natural gas reforming gasification has an excellent future perspective. Advancements in technology and increased focus on sustainable energy solutions have shaped natural gas reforming gasification into a potentially crucial means to reduce carbon emissions and transition to clean energy [6]. Integrating carbon sequestration schemes and using renewable energy sources in this process would further enhance its sustainability and contribution to the development of a circular economy [53]. Natural gas reforming is an advanced and mature production process that builds upon existing natural gas pipeline delivery infrastructure. Approximately 95% of the H2 produced in the United States is produced by natural gas reforming in large central plants, making this an essential technological pathway for near-term H2 production [6,53]. Chen et al. [54] evaluated the H2 production cost estimation frameworks of SMR, surface coal gasification, and underground coal gasification with and without carbon capture. The H2 production by SMR with 99% carbon capture is profitable, considering new production tax credits. Natural gas-based H2 production through steam CH4 reforming, autothermal reforming, and pyrolysis costs with and without carbon capture, utilization, and sequestration varied in the range of 1.48–2.55 and 1.22–2.12$/kg of H2 with production of 0.22–0.35 kg of H2/kg of fuel and a CO2-footprint of 1.84–11.4 kg of CO2/kg of H2, respectively [54].
Solar thermochemical processes use concentrated solar energy to generate high temperatures for use in thermochemical reactions to split H2O and produce H2 [55]. An enhancement in 30.8% of H2 production at 600 °C by the solar-thermochemical process was reported compared to the thermochemical process (115 mmol/h/g) [56]. The STCH project was initiated in 2003 by the Department of Energy Office of Energy Efficiency and Renewable Energy (EERE, USA) to achieve the goal of H2 production at $2/kg [57]. This method offers several advantages, including the use of renewable solar energy and the potential for large-scale H2 production. However, developing and implementing solar thermochemical H2 processes [39,58] involves challenges such as identifying suitable, efficient, and durable materials for reactors, improving conversion efficiency and reaction kinetics, and developing cost-effective systems that can be scaled up for industrial production [48,55]. Furthermore, integrating solar thermochemical H2 processes into existing energy systems and infrastructures presents logistical challenges. Despite these challenges, the solar thermochemical H2 process holds great promise for a sustainable clean-energy future [59,60]. Thus, the solar thermochemical process offers a viable pathway for large-scale H2 production by harnessing concentrated solar energy. Finding solutions to the challenges associated with solar thermochemical H2 processes through ongoing research and development could lead to improved efficiency, durability, and scalability of this technology [42]. Overall, the thermochemical H2 production routes are a well-established and mature technology but still face limitations in generating GHGs and using non-renewable resources. Further, the advancement in these systems through the integration of carbon capture and storage technologies and the employment of renewable feedstock can be beneficial to achieve high H2 production efficiency and a better environmental footprint. H2 production via thermochemical reforming involves the following reactions (Equations (1)–(5)) [39,59,60]:
Steam-CH4 reforming: CH4 + H2O + heat → 3H2 + CO
H2O-gas shift: CO + H2O → H2 + CO2 + heat
CH4 partial oxidation: CH4 + ½O2 → 2H2 + CO + heat
Ethanol steam reforming: C2H5OH + H2O + heat → 4H2 + 2CO
Biomass gasification: C6H12O6 + O2 + H2O → H2 + CO + CO2 + others

2.2. Electrolytic Routes

H2 production through electrolytic routes has recently gained significant attention because of its potential as a clean and sustainable energy source [61]. The use of electricity to split H2O into H2 and O2 through electrolysis provides a means to produce H2 without producing greenhouse gases. Thus, this method could contribute to the reduction of carbon emissions and address the global challenges associated with reliable clean energy [4,62]. Furthermore, electrolysis provides flexibility in utilizing different electricity sources for the process, including renewable energy sources such as solar and wind power. Green H2 thus produced can be used in various sectors including transportation, industry, and power generation [61]. Electrochemical H2 production processes include electrolysis systems such as alkaline, PEM, SOEC, anion exchange membrane (AEM), bipolar membrane, and microbial electrolysis cells (MECs) (Figure 2) [23,62]. In electrochemical H2 generation technologies, H2O electrolysis is a crucial process that involves electric current passing through H2O to convert into H2 and O2 in an electrolyzer system consisting of anode and cathode electrodes separated by an electrolyte. The H2O is oxidized at the anode to produce O2 and protons (H+) in the PEM, OH− in alkaline, or O2− in SOEC processes. These produced ions migrate to the cathode through the electrolyte and are reduced to H2 gas [23].
The alkaline electrolysis system is an extensively employed H2O electrolysis technology to produce H2. In principle, H2 is produced in an alkaline electrolysis cell at the cathode through the electrochemical decomposition of H2O operated by an electric current. In this system, adding alkali electrolytes such as sodium hydroxide or potassium hydroxide improved H2 production efficiency by overcoming the limited intrinsic electrolytic properties of H2O [23,62]. Asbestos materials are traditionally used to separate cathodes and anodes in the alkaline electrolysis system. Several different types of alkali electrolyzer systems are available, each with unique characteristics and advantages. PEM fuel cells and alkali electrolyzers are two types of electrochemical devices that play significant roles in producing and utilizing H2 as a clean energy source [63,64]. These are crucial components of the H2 economy and are used in various applications, such as fuel cell vehicles and stationary power generation. The proton-conducting membrane, as a solid polymer electrolyte, is used in PEM electrolysis. It has higher energy efficiency and can operate at higher current densities than alkaline electrolysis [23]. They work together in a closed-loop system as a PEM/alkali electrolyzer system, where the PEM fuel cell utilizes H2 to generate electricity and the alkali electrolyzer produces H2 by splitting H2O through electrolysis. This closed-loop system allows for the continuous production and utilization of H2, making it a sustainable and environmentally friendly energy option. Furthermore, this integrated system offers flexibility in adjusting the production and utilization of H2 according to the specific needs and demands of the application. The forward osmosis-H2O splitting system integrated with alkaline H2O electrolysis showed high purity of H2 with production at a rate of 448 Nm3/day/m2 from wastewater and specific energy consumption of 3.96 kWh/Nm3 using 1 M of KOH [65]. Increasing wind-solar hybrid H2 production by multi-state alkali electrolyzer management in 12 different scenarios, a daily average energy utilization rate reached 92.8%. This favors economic potential, with an internal return rate of 6.8% and an investment payback period of 12.9 years [66]. Aqueous room temperature synthesized transition metal dichalcogenide nanoparticles in a PEM H2O electrolyzer accomplished 1 A/cm2 of current densities at a voltage of 2.28 for MoS2 and 2.07 for RuSe2 with a long period of stability over 100 h [63]. These technologies provide a sustainable and efficient way to produce and utilize H2, contributing to the transition to a greener, more sustainable future. This H2 production technology has been used for decades at various scales with relatively low production costs.
Ceramic or SOEC electrolytes, i.e., yttria-stabilized zirconia, are used in SOEC that can be operational at high temperatures, up to 1000 °C. In thermoneutral mode, the SOEC system integration, through industrial waste heat at a steam flow of 50 kg/h and temperature of 800 °C, resulted in maximum H2 production of 2.47 kmol/h [32,67]. Here, waste heat supply to total energy consumption percentage varied from 15.5 to 20.6%. This technology showed higher energy efficiency than other electrolysis processes, but it is a less mature commercial technology and requires a more complex system.
AEM, MECs, and bipolar membrane electrolysis are developed through the advancement of electrochemical technologies. The AEM system combines the advantages of PEM and alkaline electrolysis that conduct OH− as the electrolyte [21,23,64]. It uses non-precious metal catalysts at lower temperatures, making AEM more cost-effective than PEM. AEM-based alkaline seawater electrolysis using Co/P dual-doped bifunctional catalyst (Co/P-Fe3O4@IF) achieved a high current density of 500 mA/cm2 at 1.83 V without chloride oxidation reaction, and a low energy of 4.38 KWh was spent to produce H2/m3 [68]. The inexpensive electrocatalyst bifunctional nickel copper phosphide-nickel electrocatalyst, as a non-platinum group metal, exhibited a performance of 30 mA/cm2 at 2 V with excellent operational durability over 300 h in an AEM H2O electrolyzer with a range of 95–97% retention rate and 80–800 mA/cm2 current density [69].
The MEC system uses electroactive microbes to generate H2 using organic feedstocks. In its mechanism, microbes oxidize organic substrates to create electrons and H+ at the anode that flows towards the cathode through an external circuit and ion exchange membrane to form H2, respectively [21,23]. Polydopamine, polyethyleneimine, and silver nanoparticle-coated polyvinylidene fluoride membranes-based MECs exhibit antifouling properties and result in a high H2 production rate of 2.65 m3/m3/d by improving the proton transportation of membranes [70]. Pre-fermentation effluents-based MECs showed a 34.4% superior H2-producing potential of 911 mL/g of chemical O2 demands (COD) than raw food wastewater [71]. Here, high H2 production was associated with a 2-fold enhancement of Geobacter abundance at the anode compared to the control feed. These electrochemical processes offer various benefits, including (i) H2 evolution without GHG emissions, (ii) excess of electricity from renewable sources, such as solar and wind, converts to H2, (iii) it can be scaled up depending on the diverse applications, and (iv) high-purity H2 is produced, which can be directly used in fuel cells. Still, electrochemical technologies are under various levels to improve H2 production yield, pilot-scale demonstration, and economy [21,23].
In bipolar membranes, electrolysis uses a composite membrane (anion/cation exchange layers) with a bipolar junction that allows easy H2O dissociation and efficient H2 evolution [23]. The bipolar membrane crosslinked with novel bipyridine covalent triazine frameworks exhibited maximum ionic conductivity of 143 and 48.0 mS/cm for H+ and OH− after dropping in H2SO4/NaOH at 80 °C, which resulted in a maximum current density of 1.29 A/cm2 at 2.5 V [72]. The bipolar membrane consists of cation and anion exchange layers integrated into a bipolar membrane H2O electrolyzer, which showed current densities of 250 mA/m2 for splitting sea H2O into H2 and O2 [73]. It inhibits the corrosive-free chloride generation by providing basic pH at the anode in contrast to PEM H2O electrolyzers with acidic pH, which led to the failure of the PEM system in seawater. Overall, the electrochemical routes provide a clean H2, but enhancement in H2 production efficiency and the cost-effectiveness of the system still require improvement at various levels. Ongoing development and research in these technologies, such as alkaline electrolysis and PME, are considered leading solutions to achieve economic and sustainable H2 generation.
The electrolytic route of H2 production offers several advantages, such as potentially low GHG emissions (because renewable energy sources power this process), ease of scaling up to meet the growing demand for H2 in various sectors, and opportunity for energy storage by using the surplus electricity to produce more H2, which can be stored and used later during times of high energy demand or unavailability of renewable energy sources [59,61]. Nevertheless, recent developments in H2 production via the electrolytic route need to be explored and the accompanying challenges and opportunities that arise in this field need to be understood for transitioning to a non-carbon-based economy [74,75]. Some significant progress achieved thus far includes: i) advancements in fabricating electrocatalytic materials, resulting in improved efficiency and cost-effectiveness, and ii) development of new synthesis methodologies, enabling the production of novel anodic and cathodic materials that are crucial for H2 electrogeneration [59,74,76]. In summary, these advancements have paved the way for the widespread application of this technology to achieve an H2-based economy with the flexibility to use various sources of electricity, including renewable energy sources such as solar or wind power, to generate H2. Thus, electrolytic routes are essential for achieving a green and renewable H2 production process [61,77].

2.3. Direct Solar Water-Splitting Routes

Photoelectrochemical (PEC) and photobiological processes use light as the energy source for splitting H2O into H2 and O2 [5]. Currently, these processes offer long-term promise for sustainable H2 generation with minimal environmental effects, and several are at the early stages of research [78]. PEC involves the use of specialized semiconductors, known as photoelectrochemical materials, and sunlight to split H2O to generate H2. PEC semiconductor materials resemble photovoltaic systems (solar electricity generation), but these materials are dipped in H2O-based electrolytes (sunlight energizes the H2O-splitting) [59,79]. In the textile wastewater-integrated PEC system, a developed photoanode, WO3/BiVO4/Ni-PbS, showed a high current of 5.56 mA/cm2 in phosphate buffer saline and 0.5 M of Na2SO3 at an external potential of 1.23 V with 52.2 µmol of H2/cm2 and simultaneous removal of 99.9% of total organic carbon [80]. In another study, MoSSe/MnSe heterostructure synthesized through a vacancy-controlled approach exhibited high PEC activity of −7.15 mA/cm2 at 0 V with improved H2 evolution reaction [81]. Liang et al. [82] demonstrated that the operating pressure influences bubble characteristics, bubble-induced optical losses, product gas crossover, and concentration overpotential, which is vital for PEC H2O-splitting. Further, to achieve efficient PEC water-splitting, the pressure range can be 6–8 bar to minimize losses. The dual spin-controlled chiral two-/three-dimensional perovskite-based PEC H2O-splitting system exhibited a high solar-to-H2 efficiency of 12.5% [83]. The polymer carbon nitride (g-C3N4)-based photocatalyst R-TAP-Pd(II)@g-C3N4 PEC system showed a maximum H2 generation rate of 1085 μmol/g/h in visible light, which was 278-fold beneficial compared to the control catalyst as g-C3N [84]. In relation to the solar-to-H2 pathway, PEC is a promising process that offers high conversion efficiency at low operational temperatures via particle semiconductor materials or cost-effective thin films, although PEC material cost, efficiency, and durability need to be improved to meet the desired market viability [78,85]. Ongoing research and development in this area are focused on: (i) H2 production cost management by reducing the price of materials and processing, (ii) efficiency enhancement via improved absorption of sunlight and use of appropriate surface catalysis, and (iii) durability (lifetime) improvement through the use of a protective surface coat and desirable rugged materials [61]. In photobiological processes, microorganisms such as cyanobacteria and green microalgae convert H2O (in some cases, organic matter) into H2 [86] by splitting H2O into O2 and H2 ions in the presence of sunlight. Then, the generated H2 ions combine directly or indirectly to form H2 molecules [87]. Bioelectrochemical systems (BES) use wastewater or biomass organic materials as substrates and electroactive microbes to produce H2 in a bioreactor equipped with a cathode and anode separated by an ion exchange membrane [23]. In this mechanism, at the anode, the microbes oxidize substrates to generate electrons and H+ that flow through an external circuit and an ion exchange membrane towards the cathode to form H2, respectively. A comparative analysis of bioelectrochemically and electric field-driven assisted dark fermentation reactors showed that extracellular electron transfer accounts for up to 76.3% of H2 production in BES compared to 18.7% in the electric field-based systems [88]. At the pilot scale of 150-L, the nickel-foam-based cathode improved production to 19.1 L of H2/m2/d under non-limiting substrate concentrations using industrial wastewater [89]. In BES, the H2 production enhanced from 41.4 to 642 mM/mol of total organic carbon after treatment over control [90]. Overall, the advances in photocatalyst reaction efficiency and materials science can offer promising and clean H2 production through photocatalytic routes. This emerging area can produce sustainable H2 as a critical player based on future landscape considerations. The critical challenges of photobiological H2 production include: (i) low production rate, (ii) released O2 potentially inhibiting the H2 production reaction and causing safety issues upon mixing with H2 at specific concentrations, and (iii) low solar-to-H2 efficiency [5,91,92]. To overcome these challenges, basic research has been focused on the following aspects: (i) selection of desirable strains to enhance H2 production yield through efficient sunlight utilization, (ii) improvement of H2-producing enzymes through modulation of metabolic pathways and protein engineering, and (iii) configuration and development of microbes and reactors for commercial H2 production [79,93].

2.4. Biological Route

The biological route is a promising alternative to other existing methods of H2 production [94]. These processes involve the microbial conversion of pure or biomass-derived sugars to H2 through dark fermentation or photo-fermentation. Of these, dark fermentation shows better promise and sustainability for generating H2 [95,96]. This process involves the anaerobic fermentation of organic substrates by dark fermentative bacteria, resulting in H2 production as a byproduct [97]. Using sugars or biowaste feed, a maximum output of 3.8 mol of H2/mol of hexose was obtained [95]. Clostridium, Bacillus, Caldicellulosiruptor, Thermotoga, Citrobacter, Enterobacter, and Escherichia have been studied as part of significant culture studies on dark fermentative H2 production. The non-heat pretreatment sludge dominated by acetic acid-type fermentative Thermoanaerobacterium showed high H2 production of 3.68 mol/mol of hexose without controlling pH under thermophilic conditions at 55 °C [98]. Recent developments in this field have focused on enhancing the efficiency and feasibility of dark fermentative H2 production using various strategies such as optimizing reactor design and operating conditions, exploring novel substrates (co-digestion), improving microbial consortia, and genetically engineering bacteria [99,100,101]. These advancements have helped overcome challenges such as low H2 yield and limited substrate availability. Thus, dark fermentative H2 production is a viable option for sustainable energy production [102,103]. Moreover, integrating dark fermentative H2 production with other bioprocesses such as wastewater treatment or organic waste management presents additional opportunities for maximizing overall energy output and resource utilization [104]. Nevertheless, challenges that need to be addressed for further development and commercialization of this technology include optimization of operating conditions and reactor design, enhancing microbial H2 production efficiency, addressing substrate limitations, and improving process scalability [105,106]. Furthermore, integrating dark fermentative H2 production with other renewable energy technologies such as biofuel and biogas (CH4 + CO2) production presents additional opportunities for creating sustainable and efficient energy systems [97,107,108]. Addressing these challenges and capitalizing on these opportunities would enable dark fermentative H2 production to play a significant role in the transition toward a future with more sustainable carbon-neutral energy [106,109]. Recent developments in dark fermentative H2 production have shown high potential for overcoming challenges and creating new opportunities for sustainable energy production [110,111]. The co-digestion of swine manure and food waste with tuning operational dark fermentation conditions resulted in a high purity of 83.2% and H2 yields of 276 L/kg of volatile solids (VS) [112]. Designed microbial consortia of Clostridium pasteurianum, Rhodopseudomonas palustris, and Syntrophomonas wolfei showed ~4-fold higher H2 yields of 78.6 mmoL/g of COD than the maximum H2 production by individual culture [113]. Bioprocess and metabolic engineering of Clostridium tyrobutyricum through endogenous hydrogenase overexpression resulted in the highest H2 production of 910 mmol/L from molasses [114]. Dark fermentative H2 production by Enterobacter aerogenes using immobilization supports such as ceramic balls, Persian Gulf dead coral, and ceramic saddles resulted in maximum H2 production of up to 3.11 mol/mol of hexose [115]. Under a two-stage dark fermentation and AD process, the immobilized mixed culture showed high H2 and CH4 production of 21.3 and 374 L/g vs. at a high feed loading of 80 g of COD/L of food waste hydrolysate [116]. Ongoing research is aimed at further improving efficiency, increasing H2 yield, and developing more cost-effective and scalable processes [102,117,118] to achieve a more sustainable future and transition to renewable energy sources.
Photo-fermentative H2 production is a promising renewable-energy technology that produces H2 [2,97] using photosynthetic bacteria or microalgae to convert organic compounds to H2 in the presence of light. This technology may revolutionize the method of generating and storing clean energy [87,119] as it can harness the unlimited power of sunlight to generate a clean and sustainable source of hydrogen gas. Photofermentative H2 production has several advantages, namely, high energy conversion efficiency, low carbon footprint, and utilization of diverse feedstocks [120,121]. Under photo-fermentative conditions, R. capsulatus JP 91 produced a maximum of 9.0 mol of H2/mol of glucose [122]. Important culture studies on photofermentative H2 production included Rhodobacter spp. (R. sphaeroides and R. capsulatus) and Rhodopseudomonas spp. (R. palustris and R. faecalis). However, several challenges and opportunities for further development remain in this field. A significant challenge is the low efficiency of photo-fermentative H2 production, owing to factors such as low solar energy to chemical energy conversion rates, limitations in the biological systems used, and the need for optimal growth and H2 production conditions [121,123]. Various strategies have been attempted to overcome these challenges, such as genetic engineering of bacteria to enhance their H2 production capabilities, optimizing growth conditions and nutrient availability, supplementing the production media with nanoparticles, and developing novel reactor designs to improve H2 production efficiency [124,125]. Additional areas of focus for further development include scalability and cost-effectiveness of photo-fermentative H2 production [120]. Furthermore, new strains or co-cultures of photosynthetic bacteria with higher H2 production potential are being explored [126]. Addressing these challenges could potentially enable photo-fermentative H2 production to become a sustainable and economically viable method for producing clean energy [2,127,128]. Punriboon et al. [129] showed a notable enhancement in H2 production efficiency of 17-fold (493 mL/L) for Rhodobacter pentothenatexigens KKU-SN1/1 under outdoor conditions over conventional batch mode production. The growth and H2 production potential of Rhodobacter sphaeroides KKU-PS1 is highly influenced by light intensity. Here, red light proved beneficial in high biomass accumulation and green light has a 2-fold enhancement in photo-H2 productivity compared to the control white light [130]. Multi-dimension metabolic engineering of R. sphaeroides showed a 4-fold enhancement in photo-fermentative H2 production to 17.6 L/L (3.0 mol/mol of acetate) over base strain [131]. This technology can be integrated with existing wastewater treatment systems to allow simultaneous H2 production and wastewater purification; thus, photo-fermentative H2 production is a promising renewable energy technology that can contribute to a cleaner and more sustainable future [120,132]. The complete conversion of sugars to H2 would theoretically produce 12 mol of H2 from one mol of hexose. Under dark fermentation conditions, up to 4 and 2 moles of H2 can be generated via acetate and butyrate reaction intermediates, respectively. Furthermore, the photo-fermentative process can produce up to 8 moles of H2 from 2 moles of acetate [133,134]. Thus, an integrative approach of dark fermentation followed by photo-fermentation of Chlamydomonas reinhardtii biomass yields a high H2 output of 8.3 mol of H2/mol of hexose [95,135]. The continuous sequential and co-culture dark-photo fermentations using synthetic lignocellulose hydrolysate demonstrated that the sequential process of dark and photo-fermentation exhibited a higher yield of 4.15 mol of H2/mol of hexose than co-culture dark + photo fermentation with H2 yield of 2.88 mol/mol [136]. In another study, combined dark and photo-fermentation of potato waste by E. aerogenes MTCC2822 and R. sphaeroides O.U.001 resulted in higher H2 yields of 6.31 mol/mol of hexose [137]. The biological H2-producing routes are at pilot-scale research and development with limited commercial production. The biological routes offer an eco-friendly approach to producing H2 but still face limitations in production efficiency and bioprocess scalability. Biotechnological advancements in these routes will be unlocked to achieve efficient H2 through a sustainable approach in the near future. Overall, H2 production through dark and photo-fermentative routes involves the following reactions (Equations (6)–(10)) [95,133,134,135]:
Sugar (hexose) + 6H2O (Sunlight) → 12H2 + 6CO2
hexose + 2H2O → 4H2 + 2 acetate + 2CO2
hexose → 2H2 + butyrate + 2CO2
acetate + 2H2O (light) → 4H2 + 2CO2
butyrate + 6H2O (light) → 10H2 + 4CO2
The detailed benefits and disadvantages of various H2 production routes are listed in Table 1.

3. Hydrogen Storage

H2 storage is a crucial aspect of its utilization as an alternative energy source [145]. H2 storage is carried out through various technologies in three states, including gaseous, liquid, and solid. Broadly, H2 can be stored through (i) physical-based mode, which includes compressed gas, cold/cryo compressed, and liquid H2 storages, and (ii) materials-based mode, which includes adsorbent (metal-organic framework, MOF-5), liquid organic H2 carriers (LOHCs), interstitial hydride (LaNi5H6), complex hydride (NaAlH4), and chemical H2 (NH3BH3) [23,146,147,148,149]. H2 storage as gas physically requires high-pressure tanks (350–700 bar) and a cryogenic temperature of −253 °C for liquid condition storage. It can also be stored on surfaces or within solids through adsorption or absorption [146,150].
The gaseous state of H2 storage is categorized as compressed and underground storage. Compressed H2 storage is conducted at high pressure in cylinders (individual or in cascade) or large vessels to reduce volume and enhance storage capacity [23,146]. On the other hand, underground storage implies H2 storing in geological structures or subsurface formations such as aquifers, salt caverns, and depleted oil/gas reservoirs. Aquifers are underground H2O-bearing formations, and H2 can be stored in their confined and unconfined form of origin. Alternatively, salt caverns are underground formations created as solution-mined and mined caverns consisting of salts with poor geological availability. The depleted oil/gas reservoirs pose a potential option for H2 storage because of their well-established containment assets and vast spaces [23,151].
Liquid-state H2 storage is carried out through cooling and liquefying gaseous H2 under extremely low temperatures, such as in cryogenic tanks [147,148]. The handling and requirements of specialized equipment set-up, liquid H2 storage, and transportation are similar but differ in infrastructure, period, and primary objectives. LOHCs have gained attention as promising options for H2 storage and transport. The unique chemistry and catalytic reactions of organic hydrides are well-suited for creating an H2 delivery infrastructure, especially to realize a future H2 energy-based society that widely uses renewable energy sources [152]. Moreover, LOHCs allow the use of existing infrastructure for fuel storage and transportation, reducing the need for costly and extensive infrastructure development. Several types of LOHCs have been investigated for potential applications in H2 storage and release [152,153]. These include formic acid, methanol, ethanol, toluene, and various liquid organic compounds with functional groups such as amines, amides, and imides. This type of storage system offers numerous benefits over conventional storage methods, primarily because of its ability to efficiently store and transport H2 in liquid organic substances [154,155].
LOHCs exhibit improved properties and performance for H2 storage and release. However, the selection of appropriate LOHCs depends on several factors, including specific applications, cost considerations, and safety requirements [148,156]. Significant research and development have occurred in recent years in the field of LOHCs [149,157], leading to the feasibility of proving LOHC technology in commercial demonstrators for stationary energy storage systems. However, significant efforts in fundamental and applied research are still required for H2 delivery to H2 filling stations or direct LOHC fuel cell applications [39]. The H2 storage capacity of LOHCs such as benzene/cyclohexane, toluene/methylcyclohexane, naphthalene/decalin, dibenzytoluene/perhydro-dibenzytotoluene, bisphenyl/bicyclohexyl, diphenylmethane/dicyclohexylmethane, carbazole/dodecahydro-carbazole, and N-ethycarbazole/dodecahydro-nethylcarbazole is in the range of 5.8–7.2 wt% or 47.4–65.4 kg m−3 (Table 2) [158,159,160,161]. However, numerous challenges remain in the development an efficient LOHCs technology. These include: (i) difficulty in reducing the dehydrogenation temperature and energy consumption, (ii) development of stable, efficient, and economic catalysts for hydrogenation/dehydrogenation, (iii) extremely high cost of purchasing LOHCs materials, and (iv) assessment of systems for technical, economic, and environmental performance [147,157]. Typically, petroleum- and coal-derived materials are used to prepare LOHC systems. Owing to the restrained quantum of traditional energy, novel approaches for manufacturing procedures must be evaluated [159,162]. A promising approach would be the coupling of LOHCs with technologies related to the catalytic pyrolysis of biomass, given that benzene is the fundamental unit of biomass. Exploring orientation and research ideas is vital for the development of biomass-based LOHCs [163,164]. Appropriate technologies should be established to fabricate LOHC according to the specific reaction equipment used. The use of LOHCs could effectively address the energy storage issue in the transition to renewable energy. Additionally, LOHC applications extend beyond storage and transportation [157,165]. They may also be used for stationary energy storage, H2 logistics, and on-board H2 production in various mobile applications. Overall, LOHCs offer a promising solution for the storage and transportation of H2, addressing the challenges associated with their low energy density and difficult handling. Further research and development in this area would be crucial for the widespread commercial success and implementation of LOHCs [39,159,166,167].
Lignocellulosic biomass contains lignin (15–30%), which can be easily depolymerized into aromatic compound intermediates via a thermochemical conversion pathway [163,171]. Therefore, these aromatic compounds can potentially be used for storing and releasing H2 via a pair of reversible reactions using LOHC technology [148,159]. Biomass thermal conversion conditions, such as targeted deconstruction, nitrogen doping, better catalysts, and reaction conditions, must be optimized for LOHCs. Recently, a high-silica HY zeolite-supported RuW alloy catalyst enabled the conversion of lignin to benzene with an 18.8% yield [163]. Recent significant developments in H2 storage have occurred in relation to compressed H2 storage tanks, liquid H2 storage tanks, and hydride containment systems, leading to potential advantages such as increased storage capacity, improved safety measures, and enhanced efficiency in storing H2 [157,159]. Despite these improvements, challenges and opportunities persist [39,172]. A primary challenge in H2 storage is identifying materials that enable the safe and compact storage of H2. In fact, the search for lightweight materials that can safely store H2 remains a bottleneck in the H2 economy [173]. Additionally, the cost of storage systems, particularly those capable of maintaining high-pressure H2, is concerning. Despite these challenges, advancements in H2 storage, such as the discovery of new materials, namely, complex hydrides and boranes, which offer reversible storage options and efficient H2 release, have been reported [169,174]. Furthermore, innovative technologies, such as nanoparticles and 3D-supported nanomaterials, hold promise for improving H2 storage capabilities and enhancing the feasibility of accessing underground storage [42,155,175]. Compared to gaseous H2, liquid H2 has a higher volumetric density, making transportation and storage easier. H2 carriers-based transportation offers lower flammability or explosion risk than liquid or gaseous forms of H2, which enhances safety during storage and transportation [23,151]. Developing and advancing liquefaction technologies can reduce energy inputs for converting gaseous H2 into its liquid form. This technology can be integrated through renewable energy systems and its future exploration for suitability in the space industry.
The solid-state H2 storage uses solid materials or compounds such as chemical and metal hydrides or H2 absorbed on/within porous materials [23]. In metal hydride storage methods, H2 directly interacts with metals or their alloys, such as AB2 or AB5 types, to form reversible and stable bonds that allow easy release of H2 through decreasing pressure or heating. In contrast, complex hydrides consist of metals or metalloid elements attached to H2, such as boron [i.e., LiBH4, NaBH4, and (Li2Mg(BH4)4)], aluminum (i.e., NaAlH4 and LiAlH4), and nitrogen [i.e., LiNH, LiNH2, NH3BH3, and Mg(NH2)2] [23,176]. The adsorbent materials such as zeolites, metal-organic frameworks, and activated carbons stored H2 through physisorption. This technology operates at low temperatures and pressures over liquid or gaseous H2 storage methods by achieving high density and minimal infrastructure requirements [23]. Figure 3 illustrates the various H2 storage-associated processes.

4. Hydrogen Transportation

H2 transportation has gained significant attention in recent years as a potential solution for reducing carbon emissions and addressing environmental concerns. With growing interest in renewable energy and the need for cleaner transportation options, H2 has emerged as a promising alternative fuel. Recent developments in H2 transportation have led to promising advancements in the use of H2 as a fuel for vehicles [25,177,178]. H2 transport involves various techniques for moving H2 from its point of generation to the point of use. H2 transportation is carried out through tank truckers, ships, pipelines, and tube trailers. Transportation of H2 is a crucial aspect for consideration in the economy. Various H2 transportation methods are employed, including (i) gaseous H2 transportation, which is used in the gas state of H2 transport, (ii) liquid H2 transportation, which requires cooling and liquefaction of H2 at very low temperatures, and (iii) carrier H2 transportation, which uses compounds or materials to capture and release H2 [23,150,179].
In the gaseous method, is compressed using high pressure for transportation in well-designed containers with safety standards [151]. The transport of H2 as a gas is suitable for low-volume applications because of the low H2 density in atmospheric pressure. This method is widely employed for H2 transportation through pipelines and high-pressure tube trailers due to its low cost and well-developed infrastructure. Gas compression methods commonly use mechanical (piston- and diaphragm-compressors) and centrifugal compressions [23,180]. Ionic liquid pistons and electrochemical compressions are advanced technology. The transport of H2 through pipelines can be a high capital cost due to their construction and periodic maintenance requirements, including safety measurements [23,25,176].
Liquid H2 transportation involves the transport of H2 in a fluid state using cryogenic tankers that convert gaseous H2 to a liquid form through cooling at an extremely low temperature of —253 °C [23]. Ships equipped with cryogenic tanks and insulation systems are also being created for the long-distance transport of fluid H2 in bulk. Traditional processes of H2 liquefaction require significant energy inputs and are carried out in several steps of cooling and compression systems. The various H2 liquefaction technologies include magnetic refrigeration, thermoacoustic, Linde-Hapson, Claude, Brayton, and two-stage mixed refrigerant cycles [23]. Besides gaseous and liquid H2 transportation, H2 carrier transportation offers an alternative method, using materials or compounds such as ammonia, formic acid, Mg(BH4)2, metal hydrides, and LOHCs. This type of technology is at the developmental stage over high-pressure tube trailers and pipelines such as matured or liquid transportation as an advanced technology [23,181]. H2 reacts with other elements to form various compounds, which allows it to be transported in its solid form [30,182]. For example, the transport of atomic silicon (produced using renewable energy) enables the separation of H2O into H2 and O2. Subsequently, H2 is oxidized with O2 (or air) to produce energy, with H2O as the only byproduct. Mechanochemistry refers to chemical reactions that are triggered by mechanical forces rather than heat, light, or electric potentials [177,178]. Techniques such as ball milling crush materials (e.g., boron nitride or graphene), allowing them to absorb H2 gas. The stored H2 is released by heating the powder. These methods have the potential for substantial net energy savings. However, several challenges and opportunities that are associated with H2 transport must be addressed [39,172]. The infrastructure required to support H2 transportation is a major challenge. This includes the need for H2 production facilities, storage tanks, and a network of refueling stations. Additionally, the cost of producing and distributing H2 continues to stay relatively high compared with that of traditional fuels. Nevertheless, opportunities for innovation and collaboration include the development of cost-effective production methods and the expansion of the infrastructure network [101,178]. Moreover, H2 transportation faces technical challenges regarding storage and safety. Thus, developing efficient and safe H2 storage systems is crucial for its widespread adoption in the field of transportation. H2 transportation offers the potential for zero-emission vehicles and reduces dependency on fossil fuels [13,183]. Furthermore, H2 provides longer-range capabilities for vehicles and heavier-duty trucks, which addresses the limitations of battery-electric vehicles in terms of range and load capacity. Another opportunity for H2 transportation is its potential for use as a chemical feedstock in various industries. Thus, H2 may be used as a clean and versatile input for chemical processes, enabling the decarbonization of industries such as steel production and fertilizer manufacturing [30,178]. Although challenges such as infrastructure development and storage solutions need to be overcome, significant opportunities are available for H2 transportation. These opportunities include reducing carbon emissions, achieving zero-emission vehicles, and providing longer-range capabilities for transportation [39,184]. Ongoing development and research can aim for emerging methods to enhance efficiency, cost-effectiveness, and safety in H2 transportation technology [23]. Figure 4 illustrates the various processes involved in H2 transportation.

5. Challenges, Opportunities, and Future Perspectives

The development of sustainable energy technologies, such as green approaches to producing biofuels, is required to address energy, resource, and environmental issues [185,186,187,188]. Various approaches have been demonstrated to use waste to develop biofuels and valuable chemicals in a circular economy [108,171,189,190]. H2 production is a key area of focus in the quest for sustainable and clean energy sources [97,191]. Different methods are available for producing H2, and one promising approach is the solar thermochemical process [55,59]. Recent developments in H2 production via thermochemical routes have opened new possibilities and challenges in the field of H2 economy by presenting alternative methods for large-scale H2 production using various thermochemical processes such as H2O-splitting, CH4-reforming, and biomass gasification [39]. These thermochemical routes provide sustainable and efficient H2 production opportunities while using renewable resources and minimizing carbon emissions [43,58]. Moreover, these thermochemical routes can overcome some of the limitations associated with traditional H2 production methods, such as high energy consumption and reliance on fossil fuels. However, the implementation of thermochemical routes for H2 production is not without its challenges [17,48], such as the need to optimize reaction kinetics, improve process efficiency, and address the high temperatures and pressures needed for certain thermochemical reactions [53]. Integrating thermochemical H2 production with the existing infrastructure and energy systems poses further challenges. Recent developments in thermochemical routes for H2 production present opportunities and challenges that hinder the pursuit of a sustainable and efficient H2 economy [53,58]. Through the use of biomass as a fuel source, the gasification process offers the advantages of using renewable and abundant resources. However, despite its potential benefits, biomass gasification faces several challenges that must be addressed before widespread adoption [7,8,46]. These challenges include the variability of biomass feedstock, the complex nature of gasification reactions, and the need for efficient syngas cleaning and conditioning. Therefore, further studies are needed to address these challenges and explore the full potential of biomass gasification to establish it as a viable and environment-friendly energy generation technique [7,58]. The development of efficient and sustainable methods for H2 production, such as electrocatalytic and photocatalytic H2O-splitting, is crucial for meeting the increasing global energy demand, reducing reliance on fossil fuels, and mitigating environmental issues [30,144]. The conversion of algal biomass into various biofuel products is a promising strategy for sustainable energy solutions [192,193]. Dark fermentative H2 production has emerged as a promising and sustainable method for generating H2. The use of dark fermentative bacteria for anaerobic fermentation of organic substrates has shown significant promise for producing H2 as a clean and renewable energy source [87,194,195]. Recent developments in dark and photo-fermentative H2 production have paved the way for a more efficient and sustainable method for generating H2 [196]. These advancements have opened up new possibilities for integrating dark fermentative H2 production with other renewable energy technologies, such as solar or wind power, to create integrated energy systems that are both reliable and sustainable. Additionally, the high feasibility of a circular economy has been assessed by developing biomass-based approaches to produce biofuels, including H2 and value-added products [197,198,199,200,201]. However, the primary challenge in H2 production processes is cost. Therefore, the EERE agency is focusing on developing methods to produce H2 at $2/kg and $1/kg via net-zero-carbon pathways by 2026 and 2031, respectively [202,203]. All biological H2-producing routes are at the research and development pilot scale with limited commercial production. The recent advancement in wind/solar/H2O-electrolysis routes of H2 production and technological upgradation can provide more economically green H2 below $2/kg than the biorefinery route [44,54,204]. With regard to H2 storage technologies, some studies have explored the use of LOHCs such as formic acid, methanol, ethanol, toluene, and various types of liquid organic compounds with functional groups such as amines, amides, and imides [170,205,206]. LOHCs offer various advantages and disadvantages in terms of H2 storage capacity, stability, ease of transport, and compatibility with the existing infrastructure [159,168,207]. Thus, developing effective and efficient H2 storage methods is crucial for the widespread adoption of H2 as an energy carrier [155]. The search for lightweight materials that enable safe and compact storage of H2 continues to be a challenge in H2 production [149,159,184]. In addition, developing an H2 economy has garnered significant attention in recent years as a potential solution to address the pressing challenges of climate change and energy security [204]. Public awareness and acceptance of H2 technologies are critical factors in successfully implementing an H2 economy. Therefore, the transition toward an H2 economy involves a complex interplay of technological, economic, and social factors [208,209]. Addressing safety concerns, demonstrating the environmental benefits, and fostering a positive public perception through education and outreach campaigns can help drive the widespread adoption of H2-based solutions [204,209]. Natural H2 can be produced through various activities such as decomposition, bioactivity, serpentinization, human activity, degassing, H2O reduction, radiolysis, and others [24]. Based on an estimate of peridotites in the Earth’s upper crust, a cumulative 108 Mt of H2 can be generated to supply 1000 Mt/year for 100,000 years. Still, the industrial use of natural H2 is in its primitive stages. Therefore, the role of natural H2 in energy transition may change the economic perspective significantly [24]. Overall, the major challenges in H2 production may be overcome through infrastructure development, technological advancement, and cost-competitive strategies.

6. Conclusions

H2 has emerged as a promising and sustainable alternative energy source with wide-ranging applications in various sectors such as transport and industry. Significant advancements have been achieved in H2 production technologies by focusing on efficient and environment-friendly methods. These developments include the production of H2 using renewable energy sources such as solar and wind power to perform electrolysis. Other recent developments include the implementation of novel catalysts and materials for enhanced H2 production via various pathways such as H2O-splitting, biomass conversion, and microbial processes. These advancements in H2 production contribute to reducing GHG emissions and pave the way for a future that is more sustainable and carbon-neutral. The storage of H2 is a complex and multidisciplinary field, and various methods and technologies are being explored. Research and development are ongoing in the field of H2 storage to improve its efficiency, safety, and cost-effectiveness.

Author Contributions

Conceptualization, S.K.S.P. and J.-K.L.; data curation, R.K.G., M.V.R., S.K.S.P. and J.-K.L.; writing—original draft preparation, S.K.S.P. and R.K.G.; writing—review and editing, S.K.S.P. and J.-K.L.; funding acquisition, S.K.S.P. and J.-K.L. All authors have read and agreed to the published version of the manuscript.

Funding

This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) and funded by the Ministry of Science, ICT & Future Planning (grant numbers NRF-2022M3A9I3082366, 2022M3A9I5015091, RS-2023-00222078).

Acknowledgments

This research was supported by the Consortia Research Platform (CRP) on the Energy from Agriculture (EA) program of the Indian Council of Agricultural Research (ICAR).

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Capurso, T.; Stefanizzi, M.; Torresi, M.; Camporeale, S.M. Perspective of the role of hydrogen in the 21st century energy transition. Energy Convers. Manag. 2022, 251, 114898. [Google Scholar] [CrossRef]
  2. Gupta, P.; Toksha, B.; Rahaman, M. A critical review on hydrogen based fuel cell technology and applications. Chem. Rec. 2024, 24, e202300295. [Google Scholar] [CrossRef] [PubMed]
  3. Haider, M.A.; Chaturvedi, N.D. An energy-efficient and cleaner production of hydrogen by steam reforming of glycerol using Aspen Plus. Int. J. Hydrogen Energy 2024, 49, 1311–1320. [Google Scholar] [CrossRef]
  4. Kim, M.; Lee, D.; Qi, M.; Kim, J. Techno-economic analysis of anion exchange membrane electrolysis process for green hydrogen production under uncertainty. Energy Convers. Manag. 2024, 302, 118134. [Google Scholar] [CrossRef]
  5. Zhang, B.; Wang, S.; Fan, W.; Ma, W.; Liang, Z.; Shi, J.; Liao, S.; Li, C. Photoassisted oxygen reduction reaction in H2-O2 fuel cells. Angew. Chem. Int. Ed. 2016, 128, 14968–14971. [Google Scholar] [CrossRef]
  6. Feng, L.; Gu, Y.; Pang, J.; Jiang, L.; Liu, J.; Zhou, H.; Wang, B.; Babaee, S. Risk identification and safety technology for hydrogen production from natural gas reforming. ChemBioEng Rev. 2024, 11, 386–405. [Google Scholar] [CrossRef]
  7. Chaves, F.R.; Brauer, N.T.; Torres, C.; de Lasa, H. Conversion of biomass-derived tars in a fluidized catalytic post-gasification process. Catalysts 2024, 14, 202. [Google Scholar] [CrossRef]
  8. Zhu, X.; Li, Z.; Tian, Y.; Huang, X. Configuration strategy and performance analysis of combined heat and power system integrated with biomass gasification, solid oxide fuel cell, and steam power system. Processes 2024, 12, 446. [Google Scholar] [CrossRef]
  9. Zabed, H.M.; Akter, S.; Yun, J.; Zhang, G.; Zhang, Y.; Qi, X. Biogas from microalgae: Technologies, challenges and opportunities. Renew. Sustain. Energy Rev. 2020, 117, 109503. [Google Scholar] [CrossRef]
  10. Sanoja-López, K.A.; Loor-Molina, N.S.; Luque, R. An overview of photocatalyst eco-design and development for green hydrogen production. Catal. Commun. 2024, 187, 106859. [Google Scholar] [CrossRef]
  11. Sahrin, N.T.; Khoo, K.S.; Lim, J.W.; Shamsuddin, R.; Ardo, F.M.; Rawindran, H.; Hassan, M.; Kiatkittipong, W.; Abdelfattah, E.A.; Oh, W.D.; et al. Current perspectives, future challenges and key technologies of biohydrogen production for building a carbon–neutral future: A review. Bioresour. Technol. 2022, 364, 128088. [Google Scholar]
  12. Salman, M.S.; Rambhujun, N.; Pratthana, C.; Srivastava, K.; Aguey-Zinsou, K.-F. Catalysis in liquid organic hydrogen storage: Recent advances, challenges, and perspectives. Ind. Eng. Chem. Res. 2022, 61, 6067–6105. [Google Scholar] [CrossRef]
  13. Saha, P.; Akash, F.A.; Shovon, S.M.; Monir, M.U.; Ahmed, M.T.; Khan, M.F.H.; Sarkar, S.M.; Islam, M.K.; Hasan, M.M.; Vo, D.-V.N.; et al. Grey, blue, and green hydrogen: A comprehensive review of production methods and prospects for zero-emission energy. Int. J. Green Energy 2024, 21, 1383–1397. [Google Scholar] [CrossRef]
  14. Singhvi, M.; Kim, B.S. Green hydrogen production through consolidated bioprocessing of lignocellulosic biomass using nanobiotechnology approach. Bioresour. Technol. 2022, 365, 128108. [Google Scholar] [CrossRef] [PubMed]
  15. Agrawal, D.; Mahajan, N.; Singh, S.P.; Sreedhar, I. Green hydrogen production pathways for sustainable future with net zero emissions. Fuel 2024, 359, 130131. [Google Scholar] [CrossRef]
  16. Kataya, G.; Cornu, D.; Bechelany, M.; Hijazi, A.; Issa, M. Biomass waste conversion technologies and its application for sustainable environmental development—A review. Agronomy 2023, 13, 2833. [Google Scholar] [CrossRef]
  17. Alvarado-Flores, J.J.; Alcaraz-Vera, J.V.; Ávalos-Rodríguez, M.L.; Guzmán-Mejía, E.; Rutiaga-Quiñones, J.G.; Pintor-Ibarra, L.F.; Guevara-Martínez, S.J. Thermochemical production of hydrogen from biomass: Pyrolysis and gasification. Energies 2024, 17, 537. [Google Scholar] [CrossRef]
  18. Kumar, S.S.; Lim, H. An overview of water electrolysis technologies for green hydrogen production. Energy Rep. 2022, 8, 13793–13813. [Google Scholar] [CrossRef]
  19. Emam, A.S.; Hamdan, M.O.; Abu-Nabah, B.A.; Elnajjar, E. Enhancing alkaline water electrolysis through innovative approaches and parametric study. Int. J. Hydrogen Energy 2024, 55, 1161–1173. [Google Scholar] [CrossRef]
  20. Krishnan, S.; Corona, B.; Kramer, G.J.; Junginger, M.; Koning, V. Prospective LCA of alkaline and PEM electrolyser systems. Int. J. Hydrogen Energy 2024, 55, 26–41. [Google Scholar] [CrossRef]
  21. Bin, S.; Chen, Z.; Zhu, Y.; Zhang, Y.; Xia, Y.; Gong, S.; Zhang, F.; Shi, L.; Duan, X.; Sun, Z. High-pressure proton exchange membrane water electrolysis: Current status and challenges in hydrogen production. Int. J. Hydrogen Energy 2024, 67, 390–405. [Google Scholar] [CrossRef]
  22. Chelvam, K.; Hanafiah, M.M.; Woon, K.S.; Al Ali, K. A review on the environmental performance of various hydrogen production technologies: An approach towards hydrogen economy. Energy Rep. 2024, 11, 369–383. [Google Scholar] [CrossRef]
  23. Eikeng, E.; Makhsoos, A.; Pollet, B.G. Critical and strategic raw materials for electrolysers, fuel cells, metal hydrides and hydrogen separation technologies. Int. J. Hydrogen Energy 2024, 71, 433–464. [Google Scholar] [CrossRef]
  24. Blay-Rogar, R.; Bach, W.; Bobadilla, L.F.; Reina, T.R.; Odriozola, J.A.; Amils, R.; Blay, V. Natural hydrogen in the energy transition: Fundamentals, promise, and enigmas. Renew. Sustain. Energy Rev. 2024, 189, 113888. [Google Scholar] [CrossRef]
  25. Abdalla, A.M.; Hossain, S.; Nisfindy, O.B.; Azad, A.T.; Dawood, M.; Azad, A.K. Hydrogen production, storage, transportation and key challenges with applications: A review. Energy Convers. Manag. 2018, 165, 602–627. [Google Scholar] [CrossRef]
  26. Abraham, E.J.; Linke, P.; Al-Rawashdeh, M.; Rousseau, J.; Burton, G.; Al-Mohannadi, D.M. Large-scale shipping of low-carbon fuels and carbon dioxide towards decarbonized energy systems: Perspectives and challenges. Int. J. Hydrogen Energy 2024, 63, 217–230. [Google Scholar] [CrossRef]
  27. Aziz, M. Liquid hydrogen: A review on liquefaction, storage, transportation, and safety. Energies 2021, 14, 5917. [Google Scholar] [CrossRef]
  28. Abdin, Z.; Tang, C.; Liu, Y.; Catchpole, K. Large-scale stationary hydrogen storage via liquid organic hydrogen carriers. iScience 2021, 24, 102966. [Google Scholar] [CrossRef]
  29. Han, D.J.; Jo, Y.S.; Shin, B.S.; Jang, M.; Kang, J.W.; Han, J.H.; Nam, S.W.; Yoon, C.W. A novel eutectic mixture of biphenyl and diphenylmethane as a potential liquid organic hydrogen carrier: Catalytic hydrogenation. Energy Technol. 2019, 7, 113–121. [Google Scholar] [CrossRef]
  30. Zhang, L.; Jia, C.; Bai, F.; Wang, W.; An, S.; Zhao, K.; Li, Z.; Li, J.; Sun, H. A comprehensive review of the promising clean energy carrier: Hydrogen production, transportation, storage, and utilization (HPTSU) technologies. Fuel 2024, 355, 129455. [Google Scholar] [CrossRef]
  31. Lang, C.G.; Jia, Y.; Yao, X.D. Recent advances in liquid-phase chemical hydrogen storage. Energy Storage Mater. 2020, 26, 290–312. [Google Scholar] [CrossRef]
  32. Kim, T.W.; Jeong, H.; Baik, J.H.; Suh, Y.-W. State-of-the-art catalysts for hydrogen storage in liquid organic hydrogen carriers. Chem. Lett. 2022, 51, 239–255. [Google Scholar] [CrossRef]
  33. Shimbayashi, T.; Fujita, K. Metal-catalyzed hydrogenation and dehydrogenation reactions for efficient hydrogen storage. Tetrahedron 2020, 76, 130946. [Google Scholar] [CrossRef]
  34. Sikiru, S.; Oladosu, T.L.; Amosa, T.I.; Olutoki, J.O.; Ansari, M.N.M.; Abioye, K.J.; Rehman, Z.U.; Soleimani, H. Hydrogen-powered horizons: Transformative technologies in clean energy generation, distribution, and storage for sustainable innovation. Int. J. Hydrogen Energy 2024, 56, 1152–1182. [Google Scholar] [CrossRef]
  35. Hodoshima, S.; Takaiwa, S.; Shono, A.; Satoh, K.; Saito, Y. Hydrogen storage by decalin/naphthalene pair and hydrogen supply to fuel cells by use of superheated liquid-film-type catalysis. Appl. Catal. A Gen. 2005, 283, 235–242. [Google Scholar] [CrossRef]
  36. Lee, S.; Lee, J.; Kim, T.; Han, G.; Lee, J.; Lee, K.; Bae, J. Pt/CeO2 catalyst synthesized by combustion method for dehydrogenation of perhydro-dibenzyltoluene as liquid organic hydrogen carrier: Effect of pore size and metal dispersion. Int. J. Hydrogen Energy 2021, 46, 5520–5529. [Google Scholar] [CrossRef]
  37. Kwak, Y.; Moon, S.; Ahn, C.; Kim, A.-R.; Park, Y.; Kim, Y.; Sohn, H.; Jeong, H.; Nam, S.W.; Yoon, C.W.; et al. Effect of the support properties in dehydrogenation of biphenyl-based eutectic mixture as liquid organic hydrogen carrier (LOHC) over Pt/Al2O3 catalysts. Fuel 2021, 284, 119285. [Google Scholar] [CrossRef]
  38. Perreault, P.; Van Hoecke, L.; Pourfallah, H.; Kummamuru, N.B.; Boruntea, C.-R.; Preuster, P. Critical challenges towards the commercial rollouts of a LOHC-based H2 economy. Curr. Opin. Green Sustain. Chem. 2023, 41, 100836. [Google Scholar] [CrossRef]
  39. Qureshi, F.; Yusuf, M.; Khan, M.A.; Ibrahim, H.; Ekeoma, B.C.; Kamyab, H.; Rehman, M.M.; Nadda, A.K.; Chelliapan, S. A State-of-The-Art Review on the Latest trends in Hydrogen production, storage, and transportation techniques. Fuel 2023, 340, 127574. [Google Scholar] [CrossRef]
  40. Ikuerowo, T.; Bade, S.O.; Akinmoladun, A.; Oni, B.A. The integration of wind and solar power to water electrolyzer for green hydrogen production. Int. J. Hydrogen Energy 2024, 76, 75–96. [Google Scholar] [CrossRef]
  41. Qureshi, F.; Yusuf, M.; Ibrahim, H.; Kamyab, H.; Chelliapan, S.; Pham, C.Q.; Vo, D.-V.N. Contemporary avenues of the Hydrogen industry: Opportunities and challenges in the eco-friendly approach. Environm. Res. 2023, 229, 115963. [Google Scholar] [CrossRef] [PubMed]
  42. Qureshi, F.; Yusuf, M.; Tahir, M.; Haq, M.; Mohamed, M.M.I.; Kamyab, H.; Nguyen, H.-H.T.; Vo, D.-V.N.; Ibrahim, H. Renewable hydrogen production via biological and thermochemical routes: Nanomaterials, economic analysis and challenges. Process Saf. Environ. Protect. 2023, 179, 68–88. [Google Scholar] [CrossRef]
  43. Nnabuife, S.G.; Darko, C.K.; Obiako, P.C.; Kuang, B.; Sun, X.; Jenkins, K. A comparative analysis of different hydrogen production methods and their environmental impact. Clean. Technol. 2023, 5, 1344–1380. [Google Scholar] [CrossRef]
  44. Li, F.; Liu, D.; Sun, K.; Yang, S.; Peng, F.; Zhang, K.; Guo, G.; Si, Y. Towards a future hydrogen supply chain: A review of technologies and challenges. Sustainability 2024, 16, 1890. [Google Scholar] [CrossRef]
  45. Ellacuriaga, M.; Gil, M.V.; Gómez, X. Syngas fermentation: Cleaning of syngas as a critical stage in fermentation performance. Fermentation 2023, 9, 898. [Google Scholar] [CrossRef]
  46. Marcantonio, V.; Di Paola, L.; De Falco, M.; Capocelli, M. Modeling of biomass gasification: From thermodynamics to process simulations. Energies 2023, 16, 7042. [Google Scholar] [CrossRef]
  47. Zhu, X.; Xu, M.; Hu, S.; Xia, A.; Huang, Y.; Luo, Z.; Xue, X.; Zhou, Y.; Zhu, X.; Liao, Q. A novel spent LiNixCoyMn1−x−yO2 battery-modified mesoporous Al2O3 catalyst for H2-rich syngas production from catalytic steam co-gasification of pinewood sawdust and polyethylene. Fuel 2024, 367, 123420. [Google Scholar] [CrossRef]
  48. Aboughaly, M.; Fattah, I.M.R. Environmental analysis, monitoring, and process control strategy for reduction of greenhouse gaseous emissions in thermochemical reactions. Atmosphere 2023, 14, 655. [Google Scholar] [CrossRef]
  49. de Abreu, V.H.S.; Pereira, V.G.F.; Proença, L.F.C.; Toniolo, F.S.; Santos, A.S. A systematic study on techno-economic evaluation of hydrogen production. Energies 2023, 16, 6542. [Google Scholar] [CrossRef]
  50. Detsios, N.; Maragoudaki, L.; Rebecchi, S.; Quataert, K.; DeWinter, K.; Stathopoulos, V.; Orfanoudakis, N.G.; Grammelis, P.; Atsonios, K. Techno-economic evaluation of jet fuel production via an alternative gasification-driven biomass-to-liquid pathway and benchmarking with the state-of-the-art Fischer–Tropsch and alcohol-to-Jet concepts. Energies 2024, 17, 1685. [Google Scholar] [CrossRef]
  51. Li, T.; Su, H.; Zhu, L.; Xu, D.; Ji, N.; Wang, S. Hydrogen production from steam reforming of biomass-derived levulinic acid over highly stable spinel-supported Ni catalysts. Waste Dispos. Sustain. Energy 2023, 5, 427–438. [Google Scholar] [CrossRef]
  52. Qiao, Y.; Jiang, W.; Li, Y.; Dong, X.; Yang, F. Design and analysis of steam methane reforming hydrogen liquefaction and waste heat recovery system based on liquefied natural gas cold energy. Energy 2024, 302, 131792. [Google Scholar] [CrossRef]
  53. Zhang, G.; Graham, E.J.; Mallapragada, D. H2 production through natural gas reforming and carbon capture: A techno-economic and life cycle analysis comparison. Int. J. Hydrogen Energy 2024, 49, 1288–1303. [Google Scholar] [CrossRef]
  54. Chen, F.; Chen, B.; Ma, Z.; Mehana, M. Economic assessment of clean hydrogen production from fossil fuels in the intermountain-west region, USA. Renew. Sustain. Energy Trans. 2024, 5, 100077. [Google Scholar] [CrossRef]
  55. Yadav, D.; Banerjee, R. A review of solar thermochemical processes. Renew. Sustain. Energy. Rev. 2016, 54, 497–532. [Google Scholar] [CrossRef]
  56. Dong, H.; Fang, J.; Yan, X.; Lu, B.; Liu, Q.; Liu, X. Experimental investigation of solar hydrogen production via photo-thermal driven steam methane reforming. Appl. Energy 2024, 368, 123532. [Google Scholar] [CrossRef]
  57. Ma, Z.; Davenport, P.; Saur, G. System and technoeconomic analysis of solar thermochemical hydrogen production. Renew. Energy 2022, 190, 294–308. [Google Scholar] [CrossRef]
  58. Singh, R.; Kumar, R.; Sarangi, P.K.; Kovalev, A.A.; Vivekanand, V. Effect of physical and thermal pretreatment of lignocellulosic biomass on biohydrogen production by thermochemical route: A critical review. Bioresour. Technol. 2023, 369, 128458. [Google Scholar] [CrossRef]
  59. Song, H.; Luo, S.; Huang, H.; Deng, B.; Ye, J. Solar-driven hydrogen production: Recent advances, challenges, and future perspectives. ACS Energy Lett. 2022, 7, 1043–1065. [Google Scholar] [CrossRef]
  60. Marouani, I.; Guesmi, T.; Alshammari, B.M.; Alqunun, K.; Alzamil, A.; Alturki, M.; Hadj Abdallah, H. Integration of renewable-energy-based green hydrogen into the energy future. Processes 2023, 11, 2685. [Google Scholar] [CrossRef]
  61. Zaman, S.; Huang, L.; Douka, A.I.; Yang, H.; You, B.; Xia, B.Y. Oxygen reduction electrocatalysts toward practical fuel cells: Progress and perspectives. Angew. Chem. Int. Ed. 2021, 133, 17976–17996. [Google Scholar] [CrossRef]
  62. Sharshir, S.W.; Joseph, A.; Elsayad, M.M.; Tareemi, A.A.; Kandeal, A.W.; Elkadeem, M.R. A review of recent advances in alkaline electrolyzer for green hydrogen production: Performance improvement and applications. Int. J. Hydrogen Energy 2024, 49, 458–488. [Google Scholar] [CrossRef]
  63. Li, J.; Miro, R.; Wrzesińska-Lashkova, A.; Yu, J.; Arbiol, J.; Vaynzof, Y.; Shavel, A.; Lesnyak, V. Aqueous room-temperature synthesis of transition metal dichalcogenide nanoparticles: A sustainable route to efficient hydrogen evolution. Adv. Funct. Mater. 2024. [Google Scholar] [CrossRef]
  64. Locci, C.; Mertens, M.; Höyng, S.; Schmid, G.; Bagus, T.; Lettenmeier, P. Scaling-up PEM Electrolysis Production: Challenges and Perspectives. Chem. Ing. Tech. 2024, 96, 22–29. [Google Scholar] [CrossRef]
  65. Cassol, G.S.; Shang, C.; An, A.K.; Khanzada, N.K.; Ciucci, F.; Manzotti, A.; Westerhoff, P.; Song, Y.; Liang, L. Ultra-fast green hydrogen production from municipal wastewater by an integrated forward osmosis-alkaline water electrolysis system. Nat. Commun. 2024, 15, 2617. [Google Scholar] [CrossRef] [PubMed]
  66. Su, W.; Li, Q.; Zheng, W.; Han, Y.; Yu, Z.; Bai, Z.; Han, Y. Enhancing wind-solar hybrid hydrogen production through multi-state electrolyzer management and complementary energy optimization. Energy Rep. 2024, 11, 1774–1786. [Google Scholar] [CrossRef]
  67. Wu, C.; Zhu, Q.; Dou, B.; Fu, Z.; Wang, J.; Mao, S. Thermodynamic analysis of a solid oxide electrolysis cell system in thermoneutral mode integrated with industrial waste heat for hydrogen production. Energy 2024, 301, 131678. [Google Scholar] [CrossRef]
  68. Xie, Z.; Ding, L.; Yu, S.; Wang, W.; Capuano, C.B.; Keane, A.; Ayers, K.; Cullen, D.A.; Mayer III, H.M.; Zhang, F.-Y. Ionomer-free nanoporous iridium nanosheet electrodes with boosted performance and catalyst utilization for high-efficiency water electrolyzers. Appl. Catal. B Environ. 2024, 341, 123298. [Google Scholar] [CrossRef]
  69. Singh, K.; Selvaraj, K. Tensile nanostructured hierarchically porous non-precious transition metal-based electrocatalyst for durable anion exchange membrane-based water electrolysis. J. Colloid. Interface Sci. 2024, 664, 389–399. [Google Scholar] [CrossRef]
  70. Zhao, N.; Meng, S.; Li, X.; Liu, H.; Liang, D. Enhancing proton transport in polyvinylidenedifluoride membranes and reducing biofouling for improved hydrogen production in microbial electrolysis cells. Bioresour. Technol. 2024, 402, 130842. [Google Scholar] [CrossRef]
  71. Cha, J.; Choi, Y.; Park, H.; Kim, D.; Baek, G.; Lee, C. Combining pre-fermentation and microbial electrolysis for efficient hydrogen production from food wastewater. Process Safety Environ. Prot. 2024, 187, 1471–1480. [Google Scholar] [CrossRef]
  72. Wei, W.; Nan, S.; Su, X.; He, R. Covalently crosslinking of sulfonated poly (4,4′-diphenylether-5,5′-bibenzimidazole) with triazine frameworks for using as the diaphragm in amphoteric water electrolytic cells. J. Membr. Sci. 2024, 702, 122791. [Google Scholar] [CrossRef]
  73. Marin, D.H.; Perryman, J.T.; Hubert, M.A.; Lindquist, G.A.; Chen, L.; Aleman, A.M.; Kamat, G.A.; Niemann, V.A.; Stevens, M.B.; Regmi, Y.N.; et al. Hydrogen production with seawater-resilient bipolar membrane electrolyzers. Joule 2023, 7, 765–781. [Google Scholar] [CrossRef]
  74. Yan, Y.; Lin, B.; Zhang, L.; Wang, Y.; Zhang, H.; Zheng, H.; Zhou, T.; Zhan, Y.; Yu, Z.; Kuang, Y.; et al. Electrochemical oxidation processes based on renewable energy towards carbon neutrality: Oxidation fundamentals, catalysts, challenges and prospects. Chem. Eng. J. 2024, 487, 150447. [Google Scholar] [CrossRef]
  75. Badwal, S.P.S.; Gidden, S.; Munnings, C. Hydrogen production via solid electrolytic routes. Wires Energy Environ. 2013, 2, 473–487. [Google Scholar] [CrossRef]
  76. Esfandiari, N.; Aliofkhazraei, M.; Colli, A.N.; Walsh, F.C.; Cherevko, S.; Kibler, L.A.; Elnagar, M.M.; Lund, P.D.; Zhang, D.; Omanovic, S.; et al. Metal-based cathodes for hydrogen production by alkaline water electrolysis: Review of materials, degradation mechanism, and durability tests. Process Mater. Sci. 2024. [Google Scholar] [CrossRef]
  77. Yang, E.; Chon, K.; Kim, K.-Y.; Le, G.T.H.; Nguyen, H.Y.; Le, T.T.Q.; Nguyen, H.T.T.; Jae, M.-R.; Ahmad, I.; Oh, S.-E.; et al. Pretreatments of lignocellulosic and algal biomasses for sustainable biohydrogen production: Recent progress, carbon neutrality, and circular economy. Bioresour. Technol. 2023, 369, 128380. [Google Scholar] [CrossRef]
  78. Tuo, Y.; Chen, W.; Mishra, N.; Wang, B.; Zhang, J. Editorial: Advanced catalytic materials and processes in hydrogen technology. Front. Chem. 2023, 11, 1314796. [Google Scholar] [CrossRef]
  79. Zore, U.K.; Yedire, S.G.; Pandi, N.; Manickam, S.; Sonawane, S.H. A review on recent advances in hydrogen energy, fuel cell, biofuel and fuel refining via ultrasound process intensification. Ultrason. Sonochem. 2021, 73, 105536. [Google Scholar] [CrossRef]
  80. Ranga, M.; Sinha, S. Photoelectrochemical integrated treatment of textile wastewater by prepared optimized Ni-doped PbS quantum dots on WO3/BiVO4 along with H2 production. Separ. Purif. Technol. 2025, 352, 127928. [Google Scholar] [CrossRef]
  81. Lu, G.; Yang, H.; Zhang, J.; Xu, J.; Xie, H. Vacancy controlled MoSSe/MnSe heterostructure show boosting activities in photoelectrochemical and electrocatalytic hydrogen production. Separ. Purif. Technol. 2025, 352, 128165. [Google Scholar] [CrossRef]
  82. Liang, F.; van de Krol, R.; Abdi, F.F. Assessing elevated pressure impact on photoelectrochemical water splitting via multiphysics modeling. Nat. Commun. 2024, 15, 4944. [Google Scholar] [CrossRef]
  83. Lee, H.; Lee, C.U.; Yun, J.; Jeong, C.-S.; Jeong, W.; Son, J.; Park, Y.S.; Moon, S.; Lee, S.; Kim, J.H.; et al. A dual spin-controlled chiral two-/threedimensional perovskite artificial leaf for efficient overall photoelectrochemical water splitting. Nat. Commun. 2024, 15, 4672. [Google Scholar] [CrossRef]
  84. Zhou, X.; Yu, X.; Peng, L.; Luo, J.; Ning, X.; Fan, X.; Zhou, X.; Zhou, X. Pd(II) coordination molecule modified g-C3N4 for boosting photocatalytic hydrogen production. J. Colloid. Interface Sci. 2024, 671, 134–144. [Google Scholar] [CrossRef]
  85. Truong, D.; Changey, F.; Rondags, E.; Framboisier, X.; Etienne, M.; Guedon, E. Evaluation of short-circuited electrodes in combination with dark fermentation for promoting biohydrogen production process. Bioelectrochemistry 2024, 157, 108631. [Google Scholar] [CrossRef]
  86. Dong, X.; Pang, D.; Luo, G.; Zhu, X. Microbial water electrolysis cells for efficient wastewater treatment and H2 production. ACS Sustain. Chem. Eng. 2024, 12, 4203–4212. [Google Scholar] [CrossRef]
  87. Zhang, G.; Liu, J.; Pan, X.; Abed, A.M.; Le, B.N.; Ali, H.E.; Ge, Y. Latest avenues and approaches for biohydrogen generation from algal towards sustainable energy optimization: Recent innovations, artificial intelligence, challenges, and future perspectives. Int. J. Hydrogen Energy 2023, 48, 20988–21003. [Google Scholar] [CrossRef]
  88. Lv, Y.; Feng, Q.; Li, X.; Zhao, Y.; Pan, H.; Peng, G.; Zhou, Y. Analysis of the contribution of different electron transfer pathways for hydrogen production in a bioelectrochemically assisted dark fermentation system. Int. J. Hydrogen Energy 2024, 72, 967–975. [Google Scholar] [CrossRef]
  89. Guerrero-Sodric, O.; Baeza, J.A.; Guisasola, A. Enhancing bioelectrochemical hydrogen production from industrial wastewater using Ni-foam cathodes in a microbial electrolysis cell pilot plant. Water Res. 2024, 256, 121616. [Google Scholar] [CrossRef]
  90. Renju, X.; Singh, R. (Bio)electrochemical system: A systematic approach from agricultural waste to sewage wastewater treatment with nutrients and hydrogen recovery. J. Clean. Prod. 2024, 457, 142387. [Google Scholar] [CrossRef]
  91. Cheng, D.; Ngo, H.H.; Guo, W.; Chang, S.W.; Nguyen, D.D.; Zhang, S.; Deng, S.; An, D.; Hoang, N.B. Impact factors and novel strategies for improving biohydrogen production in microbial electrolysis cells. Bioresour. Technol. 2022, 346, 126588. [Google Scholar] [CrossRef] [PubMed]
  92. Kossalbayev, B.D.; Yilmaz, G.; Sadvakasova, A.K.; Zayadan, B.K.; Belkozhayev, A.M.; Kamshybayeva, G.K.; Sainova, G.A.; Bozieva, A.M.; Alharby, H.F.; Tomo, T.; et al. Biotechnological production of hydrogen: Design features of photobioreactors and improvement of conditions for cultivating cyanobacteria. Int. J. Hydrogen Energy 2024, 49, 413–432. [Google Scholar] [CrossRef]
  93. Ayub, H.M.U.; Nizami, M.; Qyyum, M.A.; Iqbal, N.; Al-Muhtaseb, A.H.; Hasan, M. Sustainable hydrogen production via microalgae: Technological advancements, economic indicators, environmental aspects, challenges, and policy implications. Environ. Res. 2024, 244, 117815. [Google Scholar] [CrossRef] [PubMed]
  94. Banerjee, S.; Pandit, C.; Gundupalli, M.P.; Pandit, S.; Rai, N.; Lahiri, D.; Chaubey, K.K.; Joshi, S.J. Life cycle assessment of revalorization of lignocellulose for the development of biorefineries. Environ. Dev. Sustain. 2023. [Google Scholar] [CrossRef]
  95. Patel, S.K.S.; Kumar, P.; Kalia, V.C. Enhancing biological hydrogen production through complementary microbial metabolisms. Int. J. Hydrogen Energy 2012, 37, 10590–10603. [Google Scholar] [CrossRef]
  96. Mona, S.; Kumar, S.S.; Kumar, V.; Parveen, K.; Saini, N.; Deepak, B.; Pugazhendhi, A. Green technology for sustainable biohydrogen production (waste to energy): A review. Sci. Total Environ. 2020, 728, 138481. [Google Scholar] [CrossRef]
  97. Patel, S.K.S.; Das, D.; Kim, S.C.; Cho, B.-K.; Lee, J.-K.; Kalia, V.C. Integrating strategies for sustainable conversion of waste biomass into dark-fermentative hydrogen and value-added products. Renew. Sustain. Energy Rev. 2021, 150, 111491. [Google Scholar] [CrossRef]
  98. Yin, T.; Wang, W.; Guo, W.; Zhuo, S.; Cao, G.; Ren, H.; Li, J.; Xie, G.; Ding, J.; Liu, B. Enhanced Thermophilic hydrogen production by an enriched novel acetic-acid-type fermentative bacterium from inoculum sludge with nonheat pretreatment. Energy Fuels 2024, 38, 8749–8761. [Google Scholar] [CrossRef]
  99. Kumar, P.; Patel, S.K.S.; Lee, J.-K.; Kalia, V.C. Extending the limits of Bacillus for novel biotechnological applications. Biotechnol. Adv. 2013, 31, 1543–1561. [Google Scholar] [CrossRef]
  100. Patel, S.K.S.; Kumar, P.; Singh, S.; Lee, J.-K.; Kalia, V.C. Integrative approach to produce hydrogen and polyhydroxybutyrate from biowaste using defined bacterial cultures. Bioresour. Technol. 2015, 176, 136–141. [Google Scholar] [CrossRef]
  101. Rey, J.; Segura, F.; Andujar, J.M. Green hydrogen: Resources consumption, technological maturity, and regulatory framework. Energies 2023, 16, 6222. [Google Scholar] [CrossRef]
  102. Patel, S.K.S.; Kumar, P.; Mehariya, S.; Purohit, H.J.; Lee, J.-K.; Kalia, V.C. Enhancement in hydrogen production by co-cultures of Bacillus and Enterobacter. Int. J. Hydrogen Energy 2014, 39, 14663–14668. [Google Scholar] [CrossRef]
  103. Rathi, B.S.; Kumar, P.S.; Rangasamy, G.; Rajendran, S. A critical review on biohydrogen generation from biomass. Int. J. Hydrogen Energy 2024, 52, 115–138. [Google Scholar] [CrossRef]
  104. Cheng, D.; Ngo, H.H.; Guo, W.; Chang, S.W.; Nguyen, D.D.; Deng, L.; Chen, Z.; Ye, Y.; Bui, X.T.; Hoang, N.B. Advanced strategies for enhancing dark fermentative biohydrogen production from biowaste towards sustainable environment. Bioresour. Technol. 2022, 351, 127045. [Google Scholar] [CrossRef]
  105. Patel, S.K.S.; Purohit, H.J.; Kalia, V.C. Dark fermentative hydrogen production by defined mixed microbial cultures immobilized on ligno-cellulosic waste materials. Int. J. Hydrogen Energy 2010, 35, 10674–10681. [Google Scholar] [CrossRef]
  106. Rene, E.R.; Khanongnuch, R.; Race, M.; Di Capua, F.; Pugazhendhi, A. Eco-technologies for waste to energy conversion: Applying the concepts of cleaner production, circular economy, and biorefinery. Clean Technol. Environ. Policy 2023, 25, 311–312. [Google Scholar] [CrossRef]
  107. Comesaña-Gándara, B.; García-Depraect, O.; Santos-Beneit, F.; Bordel, S.; Lebrero, R.; Muñoz, R. Recent trends and advances in biogas upgrading and methanotrophs-based valorization. Chem. Eng. J. Adv. 2022, 11, 100325. [Google Scholar] [CrossRef]
  108. Patel, S.K.S.; Kalia, V.C.; Lee, J.-K. Integration of biogas derived from dark fermentation and anaerobic digestion of biowaste to enhance methanol production by methanotrophs. Bioresour. Technol. 2023, 369, 128427. [Google Scholar] [CrossRef]
  109. Cui, J.; Aziz, M. Optimal design and system-level analysis of hydrogen-based renewable energy infrastructures. Int. J. Hydrogen Energy 2024, 58, 459–469. [Google Scholar] [CrossRef]
  110. Asrul, M.A.M.; Atan, M.F.; Yun, H.A.H.; Lai, J.C.H. A review of advanced optimization strategies for fermentative biohydrogen production processes. Int. J. Hydrogen Energy 2022, 47, 16785–16804. [Google Scholar] [CrossRef]
  111. Akaniro, I.R.; Oladipo, A.A.; Onwujekwe, E.C. Metabolic engineering approaches for scale-up of fermentative biohydrogen production—A review. Int. J. Hydrogen Energy 2024, 52, 240–264. [Google Scholar] [CrossRef]
  112. Hussien, M.; Jadhav, D.A.; Le, T.T.Q.; Jang, J.H.; Jang, J.K.; Chae, K.J. Tuning dark fermentation operational conditions for improved biohydrogen yield during co-digestion of swine manure and food waste. Process Saf. Environ. Prot. 2024, 187, 1496–1507. [Google Scholar] [CrossRef]
  113. Velasco, A.; Guerra-Blanco, P.; Gonzalez, A.; Salgado-Manjarrez, E.; Aranda-Barradas, J.; Garcia-Pena, E.I. Design of a microbial photoheterotrophic consortia for biohydrogen production under nongrowing conditions: Insight into microbial associations. Int. J. Hydrogen Energy 2024, 60, 1299–1308. [Google Scholar] [CrossRef]
  114. Fu, H.; Yang, D.; Li, X.; Guo, X.; Mo, Y.; Wang, S.; Wang, J. Metabolic and process engineering of Clostridium tyrobutyricum for efficient hydrogen production from sugarcane molasses. Fuel 2024, 371, 132075. [Google Scholar] [CrossRef]
  115. Boshagh, F.; Rostami, K.; Moazami, N. Dark fermentative hydrogen production in packed-bed bioreactor using the Persian Gulf dead coral, ceramic saddle, and ceramic ball as support matrixes. Int. J. Hydrogen Energy 2024, 52, 447–456. [Google Scholar] [CrossRef]
  116. Pomdaeng, P.; Kongthong, O.; Tseng, C.-H.; Dokmaingam, P.; Chu, C.-Y. An immobilized mixed microflora approach to enhancing hydrogen and methane productions from high-strength organic loading food waste hydrolysate in series batch reactors. Int. J. Hydrogen Energy 2024, 52, 160–169. [Google Scholar] [CrossRef]
  117. Patel, S.K.S.; Lee, J.-K.; Kalia, V.C. Beyond the theoretical yields of dark-fermentative biohydrogen. Indian J. Microbiol. 2018, 58, 529–530. [Google Scholar] [CrossRef]
  118. Qyyum, M.A.; Ihsanullah, I.; Ahmad, R.; Ismail, S.; Khan, A.; Nizami, A.-S.; Tawfik, A. Biohydrogen production from real industrial wastewater: Potential bioreactors, challenges in commercialization and future directions. Int. J. Hydrogen Energy 2022, 47, 37154–37170. [Google Scholar] [CrossRef]
  119. Zhang, Q.; Liu, H.; Shui, X.; Li, Y.; Zhang, Z. Research progress of additives in photobiological hydrogen production system to enhance biohydrogen. Bioresour. Technol. 2022, 362, 127787. [Google Scholar] [CrossRef]
  120. Melitos, G.; Voulkopoulos, X.; Zabaniotou, A. Waste to sustainable biohydrogen production via photo-fermentation and biophotolysis—A systematic review. Renew. Energy Environ. Sustain. 2021, 6, 45. [Google Scholar] [CrossRef]
  121. Thanigaivel, S.; Rajendran, S.; Hoang, T.K.A.; Ahmad, A.; Luque, R. Photobiological effects of converting biomass into hydrogen—Challenges and prospects. Bioresour. Technol. 2023, 367, 128278. [Google Scholar] [CrossRef] [PubMed]
  122. Abo-Hashesh, M.; Desaunay, N.; Hallenbeck, P.C. High yield single stage conversion of glucose to hydrogen by photofermentation with continuous cultures of Rhodobacter capsulatus JP91. Bioresour. Technol. 2013, 128, 513–517. [Google Scholar] [CrossRef]
  123. Genç, Ş.; Koku, H. A preliminary techno-economic analysis of photofermentative hydrogen production. Int. J. Hydrogen Energy 2024, 52, 212–222. [Google Scholar] [CrossRef]
  124. Castello, E.; Ferraz-Junior, A.N.D.; Andreani, C.; Anzola-Rojas, M.D.P.; Borzacconi, L.; Buitrón, G.; Carrillo-Reyes, J.; Gomes, S.D.; Maintinguer, S.I.; Moreno-Andrade, I.; et al. Stability problems in the hydrogen production by dark fermentation: Possible causes and solutions. Renew. Sustain. Energy Rev. 2020, 119, 109602. [Google Scholar] [CrossRef]
  125. Bidir, M.G.; Millerjothi, N.K.; Adaramola, M.S.; Hagos, F.Y. The role of nanoparticles on biofuel production and as an additive in ternary blend fuelled diesel engine: A review. Energy Rep. 2021, 7, 3614–3627. [Google Scholar] [CrossRef]
  126. Ferreira, G.M.T.; Moreira, F.S.; Cardoso, V.L.; Batista, F.R.X. Enhancement of photo-fermentative hydrogen production with co-culture of Rhodobacter capsulatus and Rhodospirillum rubrum by using medium renewal strategy. Bioenerg. Res. 2023, 16, 1816–1828. [Google Scholar] [CrossRef]
  127. Hitam, C.N.C.; Jalil, A.A. A review on biohydrogen production through photo-fermentation of lignocellulosic biomass. Biomass Convers. Biorefinery 2023, 13, 8465–8483. [Google Scholar] [CrossRef]
  128. Ali, S.S.; Al-Tohamy, R.; Elsamahy, T.; Sun, J. Harnessing recalcitrant lignocellulosic biomass for enhanced biohydrogen production: Recent advances, challenges, and future perspective. Biotechnol. Adv. 2024, 72, 108344. [Google Scholar] [CrossRef] [PubMed]
  129. Punriboon, N.; Sawaengkaew, J.; Mahakhan, P. Outdoor biohydrogen production by thermotolerant Rhodopseudomonas pentothenatexigens KKU-SN1/1 in a cluster of ten bioreactors system. Bioprocess. Biosyst. Eng. 2024, 47, 583–596. [Google Scholar] [CrossRef]
  130. Tiang, M.F.; Hanipa, M.A.F.; Mohmod, S.S.; Zainuddin, M.T.; Lutfi, A.A.I.; Jahim, J.M.; Takriff, M.S.; Reungsang, A.; Wu, S.-Y.; Abdul, P.M. Impact of light spectra on photo-fermentative biohydrogen production by Rhodobacter sphaeroides KKU-PS1. Bioresour. Technol. 2024, 394, 130222. [Google Scholar] [CrossRef]
  131. Zhang, Y.; Wang, Z.X.; Yuan, J.; Guo, L. Multidimensional engineering of Rhodobacter sphaeroides for enhanced photo-fermentative hydrogen production. Chem. Eng. J. 2024, 488, 150852. [Google Scholar] [CrossRef]
  132. Shahzaib, M.; Nadeem, F.; Ramzan, H.; Usman, M.; Rahman, M.U.; Singhania, R.R.; Afzal, W.; Zhang, Z.; Tahir, N. Maximizing the potential of biohydrogen production through cyclic photo fermentation: An approach towards zero waste. Management 2024, 304, 118234. [Google Scholar] [CrossRef]
  133. Dinesh, G.H.; Nguyen, D.D.; Ravindran, B.; Chang, S.W.; Vo, D.-V.N.; Bach, Q.-V.; Tran, H.N.; Basu, M.J.; Mohanrasu, K.; Murugan, R.S.; et al. Simultaneous biohydrogen (H2) and bioplastic (poly-β-hydroxybutyrate-PHB) productions under dark, photo, and subsequent dark and photo fermentation utilizing various wastes. Int. J. Hydrogen Energy 2020, 45, 5840–5853. [Google Scholar] [CrossRef]
  134. Das, S.R.; Basak, N. Molecular biohydrogen production by dark and photo fermentation from wastes containing starch: Recent advancement and future perspective. Bioprocess. Biosyst. Eng. 2021, 44, 1–25. [Google Scholar] [CrossRef]
  135. Kim, M.-S.; Baek, J.-S.; Yun, Y.-S.; Sim, S.J.; Park, S.; Kim, S.-C. Hydrogen production from Chlamydomonas reinhardtii biomass using a two-step conversion process: Anaerobic conversion and photosynthetic fermentation. Int. J. Hydrogen Energy 2006, 31, 812–816. [Google Scholar] [CrossRef]
  136. Zagrodnik, R.; Duber, A. Continuous dark-photo fermentative H2 production from synthetic lignocellulose hydrolysate with different photoheterotrophic cultures: Sequential vs. co-culture processes. Fuel 2024, 290, 130105. [Google Scholar] [CrossRef]
  137. Das, S.R.; Basak, N. Optimization of process parameters for enhanced biohydrogen production using potato waste as substrate by combined dark and photo fermentation. Biomass Conver. Bioref. 2024, 14, 4791–4811. [Google Scholar] [CrossRef]
  138. Anil, S.; Indraja, S.; Singh, R.; Appari, S.; Roy, B. A review on ethanol steam reforming for hydrogen production over Ni/Al2O3 and Ni/CeO2 based catalyst powders. Int. J. Hydrogen Energy 2022, 47, 8177–8213. [Google Scholar] [CrossRef]
  139. Kim, J.; Park, J.; Qi, M.; Lee, I.; Moon, I. Process integration of an autothermal reforming hydrogen production system with cryogenic air separation and carbon dioxide capture using liquefied natural gas cold energy. Ind. Eng. Chem. Res. 2021, 60, 7257–7274. [Google Scholar] [CrossRef]
  140. Cavalcante, M.H.S.; Maccari Zelioli, Í.A.; Guimarães Filho, E.É.X.; Júnior, J.M.d.S.; Souza Vidotti, A.D.; Daltro de Freitas, A.C.; Guirardello, R. Autothermal reforming of methane: A thermodynamic study on the use of air and pure oxygen as oxidizing agents in isothermal and adiabatic systems. Methane 2023, 2, 389–403. [Google Scholar] [CrossRef]
  141. Budhraja, N.; Pal, A.; Mishra, R.S. Plasma reforming for hydrogen production: Pathways, reactors and storage. Int. J. Hydrogen Energy 2023, 48, 2467–2482. [Google Scholar] [CrossRef]
  142. Demey, H.; Ratel, G.; Lacaze, B.; Delattre, O.; Haarlemmer, G.; Roubaud, A. Hydrogen production by catalytic supercritical water gasification of black liquor-based wastewater. Energies 2023, 16, 3343. [Google Scholar] [CrossRef]
  143. Khandelwal, K.; Boahene, P.; Nanda, S.; Dalai, A.K. Hydrogen production from supercritical water gasification of model compounds of crude glycerol from biodiesel industries. Energies 2023, 16, 3746. [Google Scholar] [CrossRef]
  144. Lopez-Hidalgo, A.M.; Smoliński, A.; Sanchez, A. A meta-analysis of research trends on hydrogen production via dark fermentation. Int. J. Hydrogen Energy 2022, 47, 13300–13339. [Google Scholar] [CrossRef]
  145. Luboń, K.; Tarkowski, R.; Uliasz-Misiak, B. Impact of depth on underground hydrogen storage operations in deep aquifers. Energies 2024, 17, 1268. [Google Scholar] [CrossRef]
  146. Chen, Z.J.; Kirlikovali, K.O.; Idrees, K.B.; Wasson, M.C.; Farha, O.K. Porous materials for hydrogen storage. Chem 2022, 8, 693–716. [Google Scholar] [CrossRef]
  147. Tarhan, C.; Çil, M.A. A study on hydrogen, the clean energy of the future: Hydrogen storage methods. J. Energy Storage 2021, 40, 102676. [Google Scholar] [CrossRef]
  148. Tsogt, N.; Gbadago, D.Q.; Hwang, S. Exploring the potential of liquid organic hydrogen carrier (LOHC) system for efficient hydrogen storage and Transport: A Techno-Economic and energy analysis perspective. Energy Convers. Manag. 2024, 299, 117856. [Google Scholar] [CrossRef]
  149. Zhou, M.-J.; Miao, Y.; Gu, Y.; Xie, Y. Recent advances in reversible liquid organic hydrogen carrier systems: From hydrogen carriers to catalysts. Adv. Mater. 2024. [Google Scholar] [CrossRef]
  150. Alves, M.P.; Gul, W.; Cimini Junior, C.A.; Ha, S.K. A review on industrial perspectives and challenges on material, manufacturing, design and development of compressed hydrogen storage tanks for the transportation sector. Energies 2022, 15, 5152. [Google Scholar] [CrossRef]
  151. Shahabuddin, M.; Rhamdhani, M.A.; Brooks, G.A. Technoeconomic analysis for green hydrogen in terms of production, compression, transportation and storage considering the Australian perspective. Processes 2023, 11, 2196. [Google Scholar] [CrossRef]
  152. D’Ambra, F.; Gébel, G. Literature review: State-of-the-art hydrogen storage technologies and liquid organic hydrogen carrier (LOHC) development. Sci. Technol. Energy Trans. 2023, 78, 32. [Google Scholar] [CrossRef]
  153. Jeong, K.; Kwon, S.; Yook, H.; Lee, J.J.; Lee, J.S.; Choi, M.; Lim, H.S.; Kim, S.-J.; Kim, S.M.; Han, J.W.; et al. Promising liquid organic hydrogen carrier: Cis-Perhydro-1-(n-phenylethyl)naphthalene with High H2 capacity and improved H2 release performance through controlled diastereomers compositions. ACS Sustain. Chem. Eng. 2023, 11, 12861–12867. [Google Scholar] [CrossRef]
  154. Pawelczyk, E.; Łukasik, N.; Wysocka, I.; Rogala, A.; Gebicki, J. Recent progress on hydrogen storage and production using chemical hydrogen carriers. Energies 2022, 15, 4964. [Google Scholar] [CrossRef]
  155. Rasul, M.G.; Hazrat, M.A.; Sattar, M.A.; Jahirul, M.I.; Shearer, M.J. The future of hydrogen: Challenges on production, storage and applications. Energy Convers. Manag. 2022, 272, 116326. [Google Scholar] [CrossRef]
  156. Jander, J.H.; Kerscher, M.; Cui, J.; Wicklein, J.; Rüde, T.; Preuster, P.; Rausch, M.H.; Wasserscheid, P.; Koller, T.M.; Fröba, A.P. Viscosity, surface tension, and density of the liquid organic hydrogen carrier system based on diphenylmethane, biphenyl, and benzophenone. Int. J. Hydrogen Energy 2022, 47, 22078–22092. [Google Scholar] [CrossRef]
  157. Rakić, E.; Grilc, M.; Likozar, B. Liquid organic hydrogen carrier hydrogenation–dehydrogenation: From ab initio catalysis to reaction micro-kinetics modelling. Chem. Eng. J. 2023, 472, 144836. [Google Scholar] [CrossRef]
  158. Xia, Z.J.; Liu, H.Y.; Lu, H.F.; Zhang, Z.K.; Chen, Y.F. Study on catalytic properties and carbon deposition of Ni-Cu/SBA-15 for cyclohexane dehydrogenation. Appl. Surf. Sci. 2017, 422, 905–912. [Google Scholar] [CrossRef]
  159. Rao, P.C.; Yoon, M. Potential liquid-organic hydrogen carrier (LOHC) systems: A review on recent progress. Energies 2020, 13, 6040. [Google Scholar] [CrossRef]
  160. Dürrk, S.; Zilm, S.; Geißelbrecht, M.; Müller, K.; Preuster, P.; Bösmann, A.; Wasserscheid, P. Experimental determination of the hydrogenation/dehydrogenation—Equilibrium of the LOHC system H0/H18-dibenzyltoluene. Int. J. Hydrogen Energy 2021, 46, 32583–32594. [Google Scholar] [CrossRef]
  161. Chu, C.; Wu, K.; Luo, B.; Cao, Q.; Zhang, H. Hydrogen storage by liquid organic hydrogen carriers: Catalyst, renewable carrier, and technology—A review. Carbon. Resour. Conver. 2023, 6, 334–351. [Google Scholar] [CrossRef]
  162. Rao, P.C.; Kim, Y.; Kim, H.; Son, Y.; Choi, Y.; Na, K.; Yoon, M. Methylbenzyl naphthalene: Liquid organic hydrogen carrier for facile hydrogen storage and release. ACS Sustain. Chem. Eng. 2023, 11, 12656–12666. [Google Scholar] [CrossRef]
  163. Meng, Q.; Yan, J.; Wu, R.; Liu, H.; Sun, Y.; Wu, N.-N.; Xiang, J.; Zheng, L.; Zhang, J.; Han, B. Sustainable production of benzene from lignin. Nat. Commun. 2021, 12, 4534. [Google Scholar] [CrossRef] [PubMed]
  164. Van Hoecke, L.; Kummamuru, N.B.; Pourfallah, H.; Verbruggen, S.W.; Perreault, P. Intensified swirling reactor for the dehydrogenation of LOHC. Int. J. Hydrogen Energy 2024, 51, 611–623. [Google Scholar] [CrossRef]
  165. Makepeace, J.W.; He, T.; Weidenthaler, C.; Jensen, T.R.; Chang, F.; Vegge, T.; Ngene, P.; Kojima, Y.; Jongh, P.E.D.; Chen, P.; et al. Reversible ammonia-based and liquid organic hydrogen carriers for high-density hydrogen storage: Recent progress. Int. J. Hydrogen Energy 2019, 44, 7746–7767. [Google Scholar] [CrossRef]
  166. Tarkowski, R.; Uliasz-Misiak, B. Towards underground hydrogen storage: A review of barriers. Renew. Sustain. Energy Rev. 2022, 162, 112451. [Google Scholar] [CrossRef]
  167. Sage, V.; Patel, J.; Hazewinkel, P.; Yasin, Q.U.A.; Wang, F.; Yang, Y.; Kozielski, K.; Li, C. Recent progress and techno-economic analysis of liquid organic hydrogen carriers for Australian renewable energy export—A critical review. Int. J. Hydrogen Energy 2024, 56, 1419–1434. [Google Scholar] [CrossRef]
  168. Modisha, P.M.; Ouma, C.N.M.; Garidzirai, R.; Wasserscheid, P.; Bessarabov, D. The prospect of hydrogen storage using liquid organic hydrogen carriers. Energy Fuels 2019, 33, 2778–2796. [Google Scholar] [CrossRef]
  169. Martynenko, E.A.; Vostrikov, S.V.; Pimerzin, A.A. Hydrogen production from decalin over silica-supported platinum catalysts: A kinetic and thermodynamic study. Reac. Kinet. Mech. Cat. 2021, 133, 713–728. [Google Scholar] [CrossRef]
  170. Muller, K.; Stark, K.; Emel’yanenko, V.N.; Varfolomeev, M.A.; Zaitsau, D.H.; Shoifet, E.; Schick, C.; Verevkin, S.P.; Arlt, W. Liquid organic hydrogen carriers: Thermophysical and thermochemical studies of benzyl-and dibenzyl-toluene derivatives. Ind. Eng. Chem. Res. 2015, 54, 7967–7976. [Google Scholar] [CrossRef]
  171. Srivastava, N.; Singh, R.; Srivastava, M.; Mohammad, A.; Harakeh, S.; Singh, R.P.; Pal, D.B.; Haque, S.; Tayeb, H.H.; Moulay, M.; et al. Impact of nanomaterials on sustainable pretreatment of lignocellulosic biomass for biofuels production: An advanced approach. Bioresour. Technol. 2023, 369, 128471. [Google Scholar] [CrossRef] [PubMed]
  172. Yang, Y.; Wu, Z.; Li, R.; Wang, H.; Ren, J.; Li, B.; Yang, F.; Zhang, Z. Review on the thermal neutrality of application-oriented liquid organic hydrogen carrier for hydrogen energy storage and delivery. Res. Eng. 2023, 19, 101394. [Google Scholar] [CrossRef]
  173. Bárkányi, A.; Tarcsay, B.L.; Lovas, L.; Mérő, T.; Chován, T.; Egedy, A. Future of hydrogen economy: Simulation-based comparison of LOHC systems. Clean Technol. Environ. Policy 2024, 26, 1521–1536. [Google Scholar] [CrossRef]
  174. Yang, M.; Hunger, R.; Berrettoni, S.; Sprecher, B.; Wang, B. A review of hydrogen storage and transport technologies. Clean. Energy 2023, 7, 190–216. [Google Scholar] [CrossRef]
  175. Jahanbakhsh, A.; Potapov-Crighton, A.L.; Mosallanezhad, A.; Kaloorazi, N.T.; Maroto-Valer, M.M. Underground hydrogen storage: A UK perspective. Renew. Sustain. Energy. Rev. 2024, 189, 114001. [Google Scholar] [CrossRef]
  176. Xu, Y.; Zhou, Y.; Li, Y.; Hao, Y.; Wu, P.; Ding, Z. Magnesium-based hydrogen storage alloys: Advances, strategies, and future outlook for clean energy applications. Molecules 2024, 29, 2525. [Google Scholar] [CrossRef] [PubMed]
  177. Faye, O.; Szpunar, J.; Eduok, U. A critical review on the current technologies for the generation, storage, and transportation of hydrogen. Int. J. Hydrogen Energy 2022, 47, 13771–13802. [Google Scholar] [CrossRef]
  178. Rong, Y.; Chen, S.; Li, C.; Chen, X.; Xie, L.; Chen, J.; Long, R. Techno-economic analysis of hydrogen storage and transportation from hydrogen plant to terminal refueling station. Int. J. Hydrogen Energy 2024, 52, 547–558. [Google Scholar] [CrossRef]
  179. Dragassi, M.-C.; Royon, L.; Redolfi, M.; Ammar, S. Hydrogen storage as a key energy vector for car transportation: A tutorial review. Hydrogen 2023, 4, 831–861. [Google Scholar] [CrossRef]
  180. Rolo, I.; Costa, V.A.F.; Brito, F.P. Hydrogen-based energy systems: Current technology development status, opportunities and challenges. Energies 2024, 17, 180. [Google Scholar] [CrossRef]
  181. Noyan, O.F.; Hasan, M.M.; Pala, N. A global review of the hydrogen energy eco-system. Energies 2023, 16, 1484. [Google Scholar] [CrossRef]
  182. Li, H.; Cao, X.; Liu, Y.; Shao, Y.; Nan, Z.; Teng, L.; Peng, W.; Bian, J. Safety of hydrogen storage and transportation: An overview on mechanisms, techniques, and challenges. Energy Rep. 2022, 8, 6258–6269. [Google Scholar] [CrossRef]
  183. Yang, Y.; Yao, J.; Wang, H.; Yang, F.; Wu, Z.; Zhang, Z. Study on high hydrogen yield for large-scale hydrogen fuel storage and transportation based on liquid organic hydrogen carrier reactor. Fuel 2022, 321, 124095. [Google Scholar] [CrossRef]
  184. Elaouzy, Y.; El Fadar, A. Water-energy-carbon-cost nexus in hydrogen production, storage, transportation and utilization. Int. J. Hydrogen Energy 2024, 53, 1190–1209. [Google Scholar] [CrossRef]
  185. Patel, S.K.S.; Kalia, V.C.; Joo, J.B.; Kang, Y.C.; Lee, J.-K. Biotransformation of methane into methanol by methanotrophs immobilized on coconut coir. Bioresour. Technol. 2020, 297, 122433. [Google Scholar] [CrossRef]
  186. Patel, S.K.S.; Shanmugam, R.; Kalia, V.C.; Lee, J.-K. Methanol production by polymer-encapsulated methanotrophs from simulated biogas in the presence of methane vector. Bioresour. Technol. 2020, 304, 123022. [Google Scholar] [CrossRef]
  187. Hu, L.; Guo, S.; Wang, B.; Fu, R.; Fan, D.; Jiang, M.; Fei, Q.; Gonzalez, R. Bio-valorization of C1 gaseous substrates into bioalcohols: Potentials and challenges in reducing carbon emissions. Biotechnol. Adv. 2022, 59, 107954. [Google Scholar] [CrossRef]
  188. Dutta, N.; Usman, M.; Ashraf, M.A.; Luo, G.; El-Din, M.G.; Zhang, S. Methods to convert lignocellulosic waste into biohydrogen, biogas, bioethanol, biodiesel and value-added chemicals: A review. Environ. Chem. Lett. 2023, 21, 803–820. [Google Scholar] [CrossRef]
  189. Patel, S.K.S.; Gupta, R.K.; Kondaveeti, S.; Otari, S.V.; Kumar, A.; Kalia, V.C.; Lee, J.-K. Conversion of biogas to methanol by methanotrophs immobilized on chemically modified chitosan. Bioresour. Technol. 2020, 315, 123791. [Google Scholar] [CrossRef] [PubMed]
  190. Patel, S.K.S.; Gupta, R.K.; Kalia, V.C.; Lee, J.-K. Synthetic design of methanotroph co-cultures and their immobilization within polymers containing magnetic nanoparticles to enhance methanol production from wheat straw-based biogas. Bioresour. Technol. 2022, 364, 128032. [Google Scholar] [CrossRef] [PubMed]
  191. Patel, S.K.S.; Singh, M.; Kalia, V.C. Hydrogen and polyhydroxybutyrate producing abilities of Bacillus spp. from glucose in two stage system. Indian J. Microbiol. 2011, 51, 418–423. [Google Scholar] [CrossRef]
  192. Kaloudas, D.; Pavlova, N.; Penchovsky, R. Lignocellulose, algal biomass, biofuels and biohydrogen: A review. Environ. Chem. Lett. 2021, 19, 2809–2824. [Google Scholar] [CrossRef]
  193. Mahmood, T.; Hussain, N.; Shahbaz, A.; Mulla, S.I.; Iqbal, H.M.N.; Bilal, M. Sustainable production of biofuels from the algae-derived biomass. Bioprocess. Biosyst. Eng. 2023, 46, 1077–1097. [Google Scholar] [CrossRef] [PubMed]
  194. Niño-Navarro, C.; Chairez, I.; Christen, P.; Canul-Chan, M.; García-Peña, E.I. Enhanced hydrogen production by a sequential dark and photo fermentation process: Effects of initial feedstock composition, dilution and microbial population. Renew. Energy 2020, 147, 924–936. [Google Scholar] [CrossRef]
  195. Li, Y.; Fan, X.; Zhang, H.; Ai, F.; Jiao, Y.; Zhang, Q.; Zhang, Z. Pretreatment of corn stover by torrefaction for improving reducing sugar and biohydrogen production. Bioresour. Technol. 2022, 351, 126905. [Google Scholar] [CrossRef] [PubMed]
  196. Goveas, L.C.; Nayak, S.; Kumar, P.S.; Vinayagam, R.; Selvaraj, R.; Rangasamy, G. Recent advances in fermentative biohydrogen production. Int. J. Hydrogen Energy 2024, 54, 200–217. [Google Scholar] [CrossRef]
  197. Patel, S.K.S.; Ray, S.; Prakash, J.; Wee, J.H.; Kim, S.-Y.; Lee, J.-K.; Kalia, V.C. Co-digestion of biowastes to enhance biological hydrogen process by defined mixed bacterial cultures. Indian J. Microbiol. 2019, 59, 154–160. [Google Scholar] [CrossRef] [PubMed]
  198. Kee, S.H.; Chiongson, J.B.V.; Saludes, J.P.; Vigneswari, S.; Ramakrishna, S.; Bhubalan, K. Bioconversion of agro-industry sourced biowaste into biomaterials via microbial factories—A viable domain of circular economy. Environ. Pollut. 2021, 271, 116311. [Google Scholar] [CrossRef]
  199. Patel, S.K.S.; Gupta, R.K.; Das, D.; Lee, J.-K.; Kalia, V.C. Continuous biohydrogen production from poplar biomass hydrolysate by a defined bacterial mixture immobilized on lignocellulosic materials under non-sterile conditions. J. Clean. Prod. 2021, 287, 125037. [Google Scholar] [CrossRef]
  200. Patel, S.K.S.; Gupta, R.K.; Kalia, V.C.; Lee, J.-K. Integrating anaerobic digestion of potato peels to methanol production by methanotrophs immobilized on banana leaves. Bioresour. Technol. 2021, 232, 124550. [Google Scholar] [CrossRef]
  201. Moreira, J.B.; Santos, T.D.; Duarte, J.H.; Bezerra, P.Q.M.; de Morais, M.G.; Costa, J.A.V. Role of microalgae in circular bioeconomy: From waste treatment to biofuel production. Clean Technol. Environ. Policy 2023, 25, 427–437. [Google Scholar] [CrossRef]
  202. Ding, D.; Wu, X.-Y. Hydrogen fuel cell electric trains: Technologies, current status, and future. Appl. Energy Combust. Sci. 2024, 17, 100255. [Google Scholar] [CrossRef]
  203. Guo, L.; Su, J.; Wang, Z.; Shi, J.; Guan, X.; Cao, W.; Ou, Z. Hydrogen safety: An obstacle that must be overcome on the road towards future hydrogen economy. Int. J. Hydrogen Energy 2024, 51, 1055–1078. [Google Scholar] [CrossRef]
  204. Riera, J.A.; Lima, R.M.; Knio, O.M. A review of hydrogen production and supply chain modeling and optimization. Int. J. Hydrogen Energy 2023, 48, 13731–13755. [Google Scholar] [CrossRef]
  205. Usman, M.R. Hydrogen storage methods: Review and current status. Renew. Sustain. Energy Rev. 2022, 167, 112743. [Google Scholar] [CrossRef]
  206. Panigrahi, P.K.; Chandu, B.; Motapothula, M.R.; Puvvada, N. Potential benefits, challenges and perspectives of various methods and materials used for hydrogen storage. Energy Fuels 2024, 38, 2630–2653. [Google Scholar] [CrossRef]
  207. Papadias, D.D.; Peng, J.-K.; Ahluwalia, R.K. Hydrogen carriers: Production, transmission, decomposition, and storage. Int. J. Hydrogen Energy 2021, 46, 24169–24189. [Google Scholar] [CrossRef]
  208. Sharma, G.D.; Verma, M.; Taheri, B.; Chopra, R.; Parihar, J.S. Socio-economic aspects of hydrogen energy: An integrative review. Technol. Forecast. Soc. Chang. 2023, 192, 122574. [Google Scholar] [CrossRef]
  209. Almaraz, S.D.; Kocsis, T.; Azzaro-Pantel, C.; Szanto, Z.O. Identifying social aspects related to the hydrogen economy: Review, synthesis, and research perspectives. Int. J. Hydrogen Energy 2024, 49, 601–618. [Google Scholar] [CrossRef]
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Figure 1. Illustration of various routes for H2 production.
Figure 1. Illustration of various routes for H2 production.
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Figure 2. Illustration of H2 production through various electrolytic routes.
Figure 2. Illustration of H2 production through various electrolytic routes.
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Figure 3. Illustration of H2 storage processes.
Figure 3. Illustration of H2 storage processes.
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Figure 4. Illustration of H2 transportation processes.
Figure 4. Illustration of H2 transportation processes.
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Table 1. Hydrogen (H2) production routes, reaction conditions, benefits, and disadvantages.
Table 1. Hydrogen (H2) production routes, reaction conditions, benefits, and disadvantages.
ProcessConditionsBenefitsDisadvantagesReference
Biomass gasification600–1000 °CHighly efficient process for H2 production and operational at commercial scaleHigh capital and operational cost, catalyst deactivation, high risk of corrosion via slug formation, impure H2 production, high energy input, and CO2 emission[8,46]
Ethanol steam-reforming700–850 °C and 30–250 MPaHigh-grade H2 production, mature production technology, and operational at commercial scale High cost of metal catalysts, catalyst deactivation via coke deposition, high energy consumption, high purity required for feedstock, and high air/CO2 emission[6,138]
CH4 partial oxidation1150–1500 °CEconomically attractive process with no heat requirement, feasible at high CH4 concentration, no catalysts required, fast start-up/short response period, and entirely operational at commercial scaleCatalyst deactivation via coke deposition, low H2/CO ratio, and CO2 emission[6,30]
Autothermal-reforming800–100 °C and 40 MPaLow operation temperature, economically attractive process with no heat requirement, and feasible at CH4 concentrationRequires O2/air, catalyst deactivation, limited commercial feasibility[139,140]
Plasma-reforming>2000 °CHigh conversion efficiency and no catalysts requiredThe extensive energy input required to generate plasma, high electrode erosion, and CO2 emission[141]
Supercritical H2O gasification350–600 °C and 22 MPaHigh conversion efficiency, operation with biomass having high moisture, and low tar formationHigh capital cost and energy input, costly feedstock harvesting, and CO2 emission[142,143]
Solar thermochemical H2600–1450 °CHigh solar energy conversion efficiencySolar system constrains due to high reaction temperatures, requires advanced materials to achieve high efficiency, and high operational and component costs[57]
Alkaline electrolysis60–90 °C and 20–100 MPaLow capital cost, no catalysts requirement, and fully commercial phase technology with electrolytic efficiency of 60–75%Extensive energy input for electrolysis operation at low temperatures, corrosive electrolyte environments, low current density generation, high maintenance cost, and long response time[44,76]
Proton exchange membrane electrolysis50–90 °C and 150–300 MPaSimple design, early on the commercial phase production, and emerging technology with electrolytic efficiency of 70–90%Extensive energy input for electrolysis operation at low temperatures, use of costly membranes and catalysts, operational in acidic environments, and immature technology[4,44]
Solid oxide electrolysis500–1000 °C and <300 MPaEnergy efficient, no catalyst requirement, and eco-friendly emerging technology with electrolytic efficiency of 85–100%High capital cost and energy input, bulky system design, and immature technology[8,44]
Dark fermentationLow temperature (≤70 °C) and low pressureLow operating cost and energy input, easy reactor design, pilot-scale production, and CO2-neutralSlow bioprocess and lower yield than theoretical production[95,124,144]
Photo-fermentationLow temperature and low pressureLow operating cost, pilot-scale production, and CO2-neutralHigh capital cost for enzymatic production, slow bioprocess, and high energy input[123,127,134]
Table 2. Hydrogen storage materials and properties.
Table 2. Hydrogen storage materials and properties.
LOHC System (Storage/Carrier)Storage Capacity
(wt%)/Energy Density (kJ/g)		Number of H2 StoredReference
Benzene (C6H6)/cyclohexane (C6H12)7.19/- a3[158,168]
Toluene (C7H8)/methylcyclohexane (C7H14)6.20/7.393[168]
2-Methylindole (C9H9N)/8H-2-methylndole (C9H17N)5.76/-4[159]
Naphthalene (C10H8)/decalin (C10H18)7.30/8.755[35,169]
Biphenyl (C12H10)/bicyclohexyl (C12H22)7.27/8.766[29,156]
Carbazole (C12H8N)/dodecahydro-carbazole (C12H20N)6.70/-6[159]
Diphenylmethane (C13H12)/dicyclohexylmethane (C13H24)6.60/-6[29]
N-Propylcarbazole (C15H15N)/12H-N-propylcarbazole (C15H27N)5.43/6.556[159]
Perhydro-N-ethylcarbazole (C14H13N)/N-ethylcarbazole (C14H25N)5.80/7.006[168]
cis-Perhydro-1-(N-phenylethyl)naphthalene/trans-Perhydro-1-(N-phenylethyl)naphthalene6.49/-8[153]
Dibenzyltoluene (C21H20)/perhydrodibenzyltoluene (C21H38)6.20/7.509[36,170]
a Not available or reported.
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Patel, S.K.S.; Gupta, R.K.; Rohit, M.V.; Lee, J.-K. Recent Developments in Hydrogen Production, Storage, and Transportation: Challenges, Opportunities, and Perspectives. Fire 2024, 7, 233. https://doi.org/10.3390/fire7070233

AMA Style

Patel SKS, Gupta RK, Rohit MV, Lee J-K. Recent Developments in Hydrogen Production, Storage, and Transportation: Challenges, Opportunities, and Perspectives. Fire. 2024; 7(7):233. https://doi.org/10.3390/fire7070233

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Patel, Sanjay Kumar Singh, Rahul K. Gupta, M. V. Rohit, and Jung-Kul Lee. 2024. "Recent Developments in Hydrogen Production, Storage, and Transportation: Challenges, Opportunities, and Perspectives" Fire 7, no. 7: 233. https://doi.org/10.3390/fire7070233

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