Recycling carbon dioxide into household chemicals

A low-cost, tin-based catalyst can selectively convert carbon dioxide to three widely produced chemicals — ethanol, acetic acid and formic acid.

Lurking within the emissions from many industrial operations is an untapped resource — carbon dioxide (CO₂). A contributor of greenhouse gas and global warming, it could instead be captured and converted to value-added chemicals.

In a collaborative project involving the U.S. Department of Energy’s (DOE) Argonne National Laboratory, Northern Illinois University and Valparaiso University, scientists report a family of catalysts that efficiently converts CO₂ into ethanol, acetic acid or formic acid. These liquid hydrocarbons are among the most produced chemicals in the U.S. and are found in many commercial products. For example, ethanol is a key ingredient in numerous household products and an additive to nearly all U.S. gasoline.

The catalysts are based on tin metal deposited over a carbon support. ​“If fully developed, our catalysts could convert the CO₂ produced at various industrial sources to valuable chemicals,” said Di-Jia Liu. ​“These sources include fossil fuel power plants and bio-fermentation and waste treatment facilities.” Liu is a senior chemist at Argonne and a senior scientist in the Pritzker School of Molecular Engineering at the University of Chicago.

“Our finding of a changing reaction path by the catalyst size is unprecedented.” — Di-Jia Liu, senior chemist

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,” Liu said.

Computational and experimental studies revealed several insights into the reaction mechanisms forming the three hydrocarbons. 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.

This 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 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.

According to Liu, ​“Our ultimate goal is to use locally generated electricity from wind and solar to produce desired chemicals for local consumption.”

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.

“If we can selectively produce only the chemicals in need near the site, we can help to cut down on CO₂ transport and storage costs,” Liu noted. ​“It would truly be a win-win situation for local adopters of our technology.”

The corresponding scientific paper appeared in the Journal of the American Chemical Society. In addition to Di-Jia Liu and Chengjun Sun, authors include Haiping Xu, Jianxin Wang, Haiying He, Inhui Hwang, Yuzi Liu, Haozhe Zhang, Tao Li, John V. Muntean and Tao Xu.

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.

About Argonne’s Center for Nanoscale Materials
The Center for Nanoscale Materials is one of the five DOE Nanoscale Science Research Centers, premier national user facilities for interdisciplinary research at the nanoscale supported by the DOE Office of Science. Together the NSRCs comprise a suite of complementary facilities that provide researchers with state-of-the-art capabilities to fabricate, process, characterize and model nanoscale materials, and constitute the largest infrastructure investment of the National Nanotechnology Initiative. The NSRCs are located at DOE’s Argonne, Brookhaven, Lawrence Berkeley, Oak Ridge, Sandia and Los Alamos National Laboratories. For more information about the DOE NSRCs, please visit https://​sci​ence​.osti​.gov/​U​s​e​r​-​F​a​c​i​l​i​t​i​e​s​/​U​s​e​r​-​F​a​c​i​l​i​t​i​e​s​-​a​t​-​a​-​G​lance.

About the Advanced Photon Source

The U. S. Department of Energy Office of Science’s Advanced Photon Source (APS) at Argonne National Laboratory is one of the world’s most productive X-ray light source facilities. The APS provides high-brightness X-ray beams to a diverse community of researchers in materials science, chemistry, condensed matter physics, the life and environmental sciences, and applied research. These X-rays are ideally suited for explorations of materials and biological structures; elemental distribution; chemical, magnetic, electronic states; and a wide range of technologically important engineering systems from batteries to fuel injector sprays, all of which are the foundations of our nation’s economic, technological, and physical well-being. Each year, more than 5,000 researchers use the APS to produce over 2,000 publications detailing impactful discoveries, and solve more vital biological protein structures than users of any other X-ray light source research facility. APS scientists and engineers innovate technology that is at the heart of advancing accelerator and light-source operations. This includes the insertion devices that produce extreme-brightness X-rays prized by researchers, lenses that focus the X-rays down to a few nanometers, instrumentation that maximizes the way the X-rays interact with samples being studied, and software that gathers and manages the massive quantity of data resulting from discovery research at the APS.

This research used resources of the Advanced Photon Source, a U.S. DOE Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.

Argonne National Laboratory seeks solutions to pressing national problems in science and technology by conducting leading-edge basic and applied research in virtually every scientific discipline. Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science.

The U.S. Department of Energy’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, visit https://​ener​gy​.gov/​s​c​ience.