By merging visible light with electrochemistry, scientists have improved the transformation of carbon dioxide into useful products, leading to an unexpected finding. The research team discovered that visible light greatly enhanced a key chemical feature known as selectivity, which paves the way for advancements in CO2 conversion and various other chemical processes involved in catalysis studies and industrial production.
By merging visible light with electrochemistry, scientists have improved the transformation of carbon dioxide into useful products, leading to an unexpected finding. The research team discovered that visible light greatly enhanced a key chemical feature known as selectivity, which paves the way for advancements not only in CO2 conversion but also in many other chemical processes involved in catalysis studies and industrial production.
A method chemists use to convert CO2 into valuable goods is called electrochemical reduction. In this process, a flow of CO2 gas passes through an electrolysis cell, which breaks the CO2 along with water into carbon monoxide and hydrogen. These can then be transformed into desired hydrocarbon products, as explained by Prashant Jain, a chemistry professor at the University of Illinois Urbana-Champaign. “The reaction, however, is slow, and it requires large electrodes filled with costly catalyst materials like gold or copper. Therefore, our lab seeks ways to accelerate this process and minimize the need for expensive catalysts, making it a more feasible solution for the alternative fuels sector,” he said.
The study, authored by Jain and former graduate student Francis Alcorn and published in the Proceedings of the National Academy of Sciences, outlines a technique that integrates the effects of visible light with electrodes coated in nanoparticles of a gold-copper alloy. This combination enables a much faster CO2 reduction and allows for better control over selectivity compared to existing methods.
“These innovative electrodes function like tiny antennas that capture photons from visible light and link them to the chemical reaction process,” Jain noted.
In the laboratory, the electrodes are submerged in a mixture of CO2, water, and an electrolyte to boost conductivity. A voltage is then applied across the electrode while a visible light laser illuminates its surface. This interaction quickly produces carbon monoxide by splitting CO2 and hydrogen from the breakdown of water molecules.
“We were thrilled to observe the increase in productivity with the introduction of visible light. However, we did not anticipate that it would significantly influence chemical selectivity, which is the real breakthrough here,” Jain remarked.
In the realm of catalysis, chemical selectivity refers to a reaction’s ability to prefer one pathway or type of molecule over another. The researchers discovered that the reaction involving water that generates hydrogen gas was preferentially enhanced with light. This discovery led the team to conduct further experiments and model their findings with assistance from George Schatz, a chemistry professor at Northwestern University, and his postdoctoral researcher Sajal Kumar Giri.
“The findings indicated that visible light presents a distinct opportunity to modify the ratio of carbon monoxide to hydrogen produced, which is vital for industrial synthetic gas production,” Jain explained. “This discovery sets the stage for a more sustainable and efficient energy future.”
Utilizing light to facilitate chemical reactions isn’t without challenges, Jain cautioned. Because incorporating light into a reaction may also introduce heat, the team needed to perform meticulous measurements and controlled experiments to determine if the increased reaction rates and selectivity were due solely to the heating effect of light.
“We conducted tests both with and without the laser at the same temperature produced by light excitation and eliminated heating as a factor,” Jain confirmed. “Instead, it was the electric fields and directed charge flow from light excitement that led to enhanced productivity and improved selectivity in water splitting, a finding supported by our collaborators’ simulations,” he explained.
The research team faces various challenges moving forward. For example, the repeated usage of the nanoparticle-based electrode is likely to cause wear over time, particularly in large-scale industrial settings. Furthermore, ongoing research is needed to enhance the overall energy efficiency of the process and manage light optimally.
“What we discovered in this study introduces entirely new perspectives on electrochemistry and catalysis,” Jain stated. “By utilizing light, we not only boost the activity of the catalyst, but we also alter the selectivity in unexpected ways. This opens up new chemical possibilities for generating various products. And why limit ourselves to CO2 reduction or water splitting? This approach could be beneficial for many other catalytic processes that are critical to the chemical sector.”
Researchers Maya Chattoraj and Rachel Nixon from Illinois also played a role in this investigation. The research was supported by the National Science Foundation, the U.S. Department of Energy, the Robert C. and Carolyn J. Springborn Endowment, and the Future Interdisciplinary Research Explorations Grant.
Jain is also connected with the Materials Research Laboratory, physics, and the Illinois Quantum Information Science and Technology Center at Illinois.
