In the race to reuse carbon dioxide and curb greenhouse gas emissions, researchers are seeking ways to turn waste gases into useful chemicals.
A new study from the University of Chicago Pritzker School of Molecular Engineering (UChicago PME) takes a key step in that direction by uncovering how the microscopic behavior of water influences these chemical reactions.
The team showed that carefully controlling how water molecules cluster together in organic solvents dramatically changes what products form when carbon monoxide is electrochemically converted. It makes it possible to steer the reaction toward valuable fuels and chemicals like methane and ethylene—rather than undesired hydrogen gas.
“This insight opens up new possibilities for how we design electrolytes to convert carbon dioxide and carbon monoxide into something useful,” said Chibueze Amanchukwu, the Neubauer Family Assistant Professor of Molecular Engineering and senior author of the new study, published in the Journal of the American Chemical Society. “It’s not just about what chemicals are present, but how they’re arranged at the molecular level.”
From accident to insight
The study focused on a reaction known as carbon monoxide electroreduction, which is part of a broader process that turns the greenhouse gas carbon dioxide into more useful chemical feedstocks. This process generally converts carbon dioxide into carbon monoxide and then attempts to create chemicals like ethylene and methane – the building blocks of many industrial products.
Most previous research in this area has used water-based systems to carry out the reduction of carbon monoxide, but graduate student Hannah Fejzić tried something different: non-aqueous solvents like acetonitrile and DMSO (dimethyl sulfoxide), combined with precise amounts of added water.
The goal was to reduce a side reaction known as hydrogen evolution, which competes with the desired fuel-forming reaction, yielding hydrogen alongside the desired product and lowering the efficiency of the chemical reaction.
“What I saw instead was more interesting—some solvents led to the formation of ethylene and methane, and others didn’t. That sent me down a path to figure out why,” said Fejzić.
Using a mix of spectroscopy, molecular simulations, and electrochemical experiments, the team discovered that solvents like acetonitrile allow water molecules to cluster together rather than dispersing evenly. These “microheterogeneous” water structures enabled the efficient formation of methane and ethylene. In contrast, solvents like DMSO and DMF (N, N,-dimethylformamide) formed more uniform mixtures, where water bonded tightly with the solvent and failed to produce useful fuels. When the team measured water activity in the different solvents they found that the solvents that led to higher water activity, likeacetonitrile, supported hydrogenated product formation while those that supported lower water activity, like DMSO, did not.
“This is one of the first studies to show how water microstructure and activity within organic solvents can directly influence electrochemical product distribution,” Fejzić said.
A path to sustainable fuels and plastics
The new data on microheterogeneous water structures build off other recent advances in understanding how water’s reactivity changes in the presence of organic solvents. A better understanding of how this occurs could have implications beyond carbon monoxide reduction.
Fejzić is now working on extending the approach to carbon dioxide directly, as well as testing a broader range of solvents to further refine the reaction conditions.
Ultimately, she hopes that the findings help optimize systems that convert carbon dioxide directly into hydrocarbons—providing cleaner pathways to generate fuels and key chemicals like ethylene, which is currently derived from fossil fuels.
“Ethylene is one of the most in-demand industrial chemicals in the world,” said Fejzić. “If we can make it renewably from carbon dioxide, that would be a big step forward.”
She also hopes that the path to her conclusions inspire other chemists to follow their results in new directions.
“There was trial-and-error involved in this project,” she said. “It started with an accidental observation, but I kept following the thread to better understand the phenomena. I hope it inspires other researchers to do the same—even if the result isn’t what you expected, it might be something better.”
Citation: “Water Clustering Modulates Activity and Enables Hydrogenated Product Formation during Carbon Monoxide Electroreduction in Aprotic Media,” Fejzić et al, Journal of the American Chemical Society (JACS), May 19 2025. DOI: jacs.4c07865
Funding: This work and the researchers involved were supported by the U.S. Department of Energy Office of Science Basic Energy Sciences, Early Career Research Program (DE-SC0024103), a CIFAR Azrieli Global Scholar Award, the Catalyst Design for Decarbonization Center (CD4DC), the National Science Foundation Graduate Research Fellowship Program, the Eric and Wendy Schmidt AI in Science Postdoctoral Fellowship, a Schmidt Futures Program, and the Roberto Rocca Scholars Program