DeKalb, IL – NIU Chemistry Professor Tao Xu has a vision for a cooler, cleaner world: Give industry a financial incentive to capture its carbon dioxide (CO2) emissions by making the process profitable.
NIU Chemistry Professor Tao Xu.
Xu and his collaborators, including scientists at the U.S. Department of Energy’s (DOE) Argonne National Laboratory, aim to accomplish this by further developing a process that can turn carbon dioxide emissions into valuable products. When producing goods, the manufacturing sector emits carbon dioxide and other greenhouse gases that contribute to global warming, both by burning fossil fuels and through certain industrial processes, according to the Congressional Budget Office.
In 2020, Xu co-led a team of scientists that announced the discovery of a new electrocatalyst that converts CO2 and water into ethanol. Now the scientists have identified a family of tin-based catalysts that efficiently converts CO2 into ethanol, acetic acid or formic acid—commonly produced chemicals that are found in many commercial products. For example, ethanol is an additive to nearly all U.S. gasoline. Acetic acid is used in household cleaning products. Formic acid is used in the leather, rubber, textile and other industries.
The scientists reported their new findings recently in the Journal of the American Chemical Society.
Atomic-Level mechanism
“Through years of hard work, the NIU and Argonne team has revealed an astonishing atomic-level mechanism that selectively guides the electrocatalytic conversion of CO2 to different value-added organics, including ethanol, acetate or formate,” said Xu, who is leading a current DOE project to expand further upon the research.
Jianxin Wang and Tao Xu working in the lab at NIU.
“I’m hopeful that industrial decarbonization could be stimulated if the implementation can be a profitable process to the relevant manufacturing sectors,” he added. “The cost of creating this process would be covered by the profit from the newly created products.”
In addition to Xu, the research team on the new study included equal first authors Haiping Xu and Jianxin Wang, who both earned their Ph.D.s at NIU under Xu’s advisory. Haiping Xu was a postdoctoral researcher at Argonne, and Wang served at the laboratory as a guest graduate student. NIU Chemistry Professor Tao Li also was a member of the research team, along with additional scientists from Argonne and Valparaiso University.
Electrocatalytic conversion method
The method used by the team is called electrocatalytic conversion, meaning that CO2 conversion over a catalyst is driven by electricity. By varying the size of tin used from single atoms to ultrasmall clusters and also to larger nano-crystallites, the team could control the CO2 conversion to acetic acid, ethanol and formic acid, respectively. Selectivity for each of these chemicals was 90% or higher.
“Our finding of a changing reaction path by the catalyst size is unprecedented,” said co-author Di-Jia Liu, a senior chemist at Argonne and a senior scientist in the Pritzker School of Molecular Engineering at the University of Chicago.
Computational and experimental studies revealed several insights into the reaction mechanisms forming the three organic chemicals. One important insight was that the reaction path completely changes when the ordinary water used in the conversion is switched to deuterated water (deuterium is an isotope of hydrogen). This phenomenon is known as the kinetic isotope effect. It has never been previously observed in CO2 conversion.
Capture of chemical and electronic structures
The research benefited from two DOE Office of Science user facilities at Argonne— the Advanced Photon Source (APS) and Center for Nanoscale Materials (CNM).
“Using the hard X-ray beams available at the APS, we captured the chemical and electronic structures of the tin-based catalysts with different tin loadings,” said co-author Chengjun Sun, an Argonne physicist. In addition, the high spatial resolution possible with a transmission electron microscope at CNM directly imaged the arrangement of tin atoms, from single atoms to small clusters, with the different catalyst loadings.
The scientists’ goal is to use locally generated electricity from wind and solar to produce desired chemicals. This would require integrating the newly discovered catalysts into a low-temperature electrolyzer to carry out the CO2 conversion with electricity supplied by renewable energy. Low-temperature electrolyzers can operate at near ambient temperature and pressure. This allows rapid start and stop to accommodate the intermittent supply of renewable energy. It is an ideal technology to serve this purpose.
“This scientific discovery and its further applications could lead to profitable industrial decarbonization or even carbon negative manufacturing,” Xu said.
Support for the research came from DOE’s Office of Energy Efficiency and Renewable Energy under the Advanced Manufacturing Office, Industrial Efficiency & Decarbonization Office. Additional support was provided by Argonne’s Laboratory Directed Research and Development fund.
Media Contact: Tom Parisi
About NIU
Northern Illinois University is a student-centered, nationally recognized public research university, with expertise that benefits its region and spans the globe in a wide variety of fields, including the sciences, humanities, arts, business, engineering, education, health and law. Through its main campus in DeKalb, Illinois, and education centers for students and working professionals in Chicago, Naperville, Oregon and Rockford, NIU offers more than 100 areas of study while serving a diverse and international student body.
