Scientists have identified a new way to improve the process for using sunlight to make a liquid fuel from carbon dioxide. Researchers showed that three-dimensional silicon scaffolds on photoelectrodes improve the yield of the desired products of chemical reactions.

Two examples of silicon photoelectrodes. Left: Micropillar silicon with cobalt catalysts reduces carbon dioxide (CO₂) to methanol (CH₃OH). Right: Porous silicon with rhenium catalysts reduces carbon dioxide (CO₂) to carbon monoxide (CO). Credit: Image courtesy of Daniel Kurtz, Bo Shang, and Eleanor Stewart-Jones

Notably, the process can convert carbon dioxide to methanol, which can potentially be used as a fuel. In addition, the process allows researchers to study the catalysts on the photoelectrodes at the molecular level. The photoelectrodes represent a state-of-the-art approach to liquid solar fuel generation.

While scientists have known of high-surface area silicon for many decades, they have not used these materials as light absorbing semiconductors for liquid fuel formation. Research carried out by the Center for Hybrid Approaches in Solar Energy to Liquid Fuels (CHASE) demonstrates that high-surface area silicon materials have important benefits for use in hybrid photoelectrodes.

In the first example, a cobalt catalyst deposited on silicon micropillars reduces carbon dioxide to methanol with improved current density providing the state-of-the-art photoelectrode for potential liquid fuel generation. The second hybrid photoelectrode example consisted of a rhenium catalyst integrated with nanoporous silicon. This example reduced carbon dioxide to carbon monoxide with high selectivity and durability.

Together, these studies demonstrate that there are inherent advantages to building higher surface area silicon semiconductors for application in hybrid photoelectrodes. This research is an important step toward generating liquid fuels using sunlight as the energy source and only the carbon dioxide and water in the air as the inputs.

This work was primarily supported as part of CHASE, an Energy Innovation Hub funded by the Department of Energy (DOE) Office of Science, Office of Basic Energy Sciences. Funding for equipment used in this research was provided by DOE, the US National Institutes of Health, the Air Force Office of Scientific Research, and the National Science Foundation.

AFM characterization work was supported by the US National Science Foundation and by the US-Israel Binational Science Foundation.

Resources

• Jia, Xiaofan, Stewart-Jones, Eleanor, Alvarez-Hernandez, Jose L., Bein, Gabriella P., Dempsey, Jillian L., Donley, Carrie L., Hazari, Nilay, Houck, Madison N., Li, Min, Mayer, James M., Nedzbala, Hannah S., and Powers, Rebecca E. Photoelectrochemical CO₂ Reduction to CO Enabled by a Molecular Catalyst Attached to High-Surface-Area Porous Silicon. United States: N. p., 2024. Web. doi: 10.1021/jacs.3c10837.

• Shang, Bo, Zhao, Fengyi, Suo, Sa, Gao, Yuanzuo, Sheehan, Colton, Jeon, Sungho, Li, Jing, Rooney, Conor L., Leitner, Oliver, Xiao, Langqiu, Fan, Hanqing, Elimelech, Menachem, Wang, Leizhi, Meyer, Gerald J., Stach, Eric A., Mallouk, Thomas E., Lian, Tianquan, and Wang, Hailiang. Tailoring Interfaces for Enhanced Methanol Production from Photoelectrochemical CO₂ Reduction. United States: N. p., 2024. Web. doi: 10.1021/jacs.3c13540.