Add visible light energy to your carbon dioxide recycling process and you get a two-for-one deal

By combining visible light and electrochemistry, researchers accelerated the conversion of carbon dioxide into valuable products and stumbled upon a surprising discovery. The research team shows that visible light significantly improves an important chemical property called selectivity, opening new avenues not only for CO2 conversion but also for many other chemical reactions used in catalysis research and chemical manufacturing. I discovered that.

One way chemists recycle CO2 into valuable products is through a process called electrochemical reduction. In this process, a stream of CO2 gas passes through an electrolysis cell, splitting CO2 and water into carbon monoxide and hydrogen, which can then be used to create new desired products. Prashant Jain, a chemistry professor at the University of Illinois at Urbana-Champaign, says that hydrocarbon products:

“However, the reaction is slow, and the process requires large electrodes containing lots of expensive catalytic materials such as gold and copper. Therefore, our lab has developed methods to speed up the process by reducing the required catalytic materials. “We’ve been pursuing ways to make this a more viable option for the alternative fuel industry,” Jain said.

The new research, led by Jain and former graduate student Francis Alcorn and published in the Proceedings of the National Academy of Sciences, combines electrodes coated with gold-copper alloy nanoparticles with the action of visible light to induce CO2 reduction. The method to do so is detailed. This is a much higher ratio than seen with current methods, allowing for more controlled selectivity.

“These new electrodes act like tiny antennas that seek out photons in the visible light range and link them into chemical reaction pathways,” Jain said.

In the lab, electrodes are soaked in a solution of CO2, water, and electrolytes to increase conductivity. The team then applied a voltage between the electrodes while a visible light laser illuminated the surface of the electrodes. The resulting reactions rapidly produce carbon monoxide from the decomposition of CO2 and hydrogen from the decomposition of water molecules.

“We were very excited to see that using visible light would increase productivity. However, we did not expect that using visible light would have such a significant impact on chemoselectivity. This is an important advance. ” said Jain.

In catalysis, chemoselectivity is the ability of a chemical reaction to favor or target one type of pathway or molecule over another. In this study, researchers discovered that the use of light selectively accelerates the water splitting reaction that produces hydrogen gas. This led the team to further experiments and model the results with the help of Northwestern University chemistry professor George Schatz and postdoctoral researcher Sajal Kumar Giri.

“This result suggests that visible light provides a unique opportunity to tune the ratio of carbon monoxide to hydrogen gas produced, a critical factor for the industrial production of syngas.” he said. “This discovery paves the way for a more sustainable and efficient energy future.”

But using light to accelerate chemical reactions is not without controversy, Jain says. Because adding light to a chemical reaction also adds heat, the team said careful measurements and controlled experiments will help determine whether it is simply the heating effect of the light that led to the increased reaction rate and selectivity. was essential for.

“We ran experiments with and without a laser at exactly the same temperatures produced by optical excitation, ruling out the possibility that heating was the cause,” Jain said. “Rather, the electric field and directional charge flow induced by photoexcitation are responsible for the increased productivity and selectivity of water splitting, which is captured in our collaborators’ simulations. .”

The team still faces some challenges moving forward. For example, repeated use of nanoparticle-based electrodes will inevitably lead to degradation over time, especially in large-scale scenarios required for industrial applications. Additionally, energy efficiency and lighting management throughout the process require further research and improvement.

“What we discovered in this study presents an entirely new way of thinking about electrochemistry and catalysis,” Jain said. “By using light, we increase the activity of this catalyst, but surprisingly, we also change its selectivity. This opens up new chemical routes for producing a variety of products. Why stop at CO2 reduction and water splitting? This could be applied to many things.” So are other catalytic reactions important to the chemical industry. ”