Scientists Borrow Nature's Playbook To Transform Carbon Dioxide Into Useful Chemicals

Scientists at UNC-Chapel Hill and the University of Pennsylvania have developed a new way to turn carbon dioxide into a more useful chemical while reducing waste, an advance that could make future carbon recycling technologies more practical and efficient.

The ACS Central Science study, “Controlled Acidity Gradients Enable CO₂ Reduction to Formic Acid (Not Formate) by Molecular Electrocatalysts,” introduces a strategy inspired by nature that carefully controls where acidity evolves inside an electrochemical system.

The study, which was conducted through the Center for Hybrid Approaches in Solar Energy to Liquid Fuels (CHASE), an Energy Innovation Hub funded by the U.S. Department of Energy, was led by the research groups of Alex Miller and René Lopez at UNC-Chapel Hill and Thomas Mallouk at the University of Pennsylvania, with co-authors Amanda Arnoff of UPenn, and Sergi Fernández, Pablo Fernandez, Elizabeth Scholer, Charlotte Montgomery and Jillian Dempsey of UNC-Chapel Hill.

The advance could help make it easier to convert carbon dioxide into useful fuels and industrial chemicals while using less energy and producing fewer unwanted byproducts. More broadly, the research shows how a better understanding of chemical reactions at the molecular level can lead to practical technologies that support cleaner energy.

“This work is significant because it showcases how advances in catalysis can be achieved by combining fundamental understanding of a molecular catalyst with a systems-level perspective,” said Dr. Jillian Dempsey, director of CHASE and Francis Preston Venable Distinguished Professor. “Overcoming the challenges of generating formic acid electrochemically opens the doors for new fuel production strategies within CHASE.”

The researchers developed a new method to prepare formic acid from carbon dioxide, an inexpensive and attractive carbon source. Formic acid is already used in manufacturing, can serve to store hydrogen for clean energy applications and can act as an important building block for producing other useful chemicals. Despite its value, making formic acid directly from carbon dioxide has been surprisingly difficult. If the reaction is carried out in a highly acidic environment, it tends to produce hydrogen gas instead of the desired product. To avoid that problem, scientists usually perform the reaction under less acidic conditions, but that produces formate instead of formic acid, along with unwanted carbonate salts that waste carbon dioxide and require extra energy to remove.

The team’s solution was inspired by the way living cells separate different chemical processes using biological membranes. In plants, for example, photosynthesis carefully keeps more and less acidic environments apart so that each reaction happens under the right conditions. The researchers borrowed that idea by designing a system that creates areas with different levels of acidity inside the device, allowing each part of the chemical reaction to happen under the best conditions.

The system contains two liquids separated by a special membrane. When electricity is applied, hydrogen ions—tiny particles that make liquids more acidic—move through the membrane but spread slowly, much like a drop of food coloring slowly dispersing in still water. That creates a small acidic zone exactly where it is needed, allowing carbon dioxide to be converted efficiently while avoiding unwanted chemical reactions. The hydrogen ions then combine with the converted carbon dioxide to produce formic acid.

“The key challenge was to understand how the acidity gradient develops to be able to control it instead of simply making the entire reaction more acidic,” said Dr. Sergi Fernandez, a former postdoc in the Miller group who now works at the University of Girona. “By creating a carefully managed acidity gradient, we were able to produce formic acid directly while greatly reducing the formation of unwanted carbonate waste.”

The researchers demonstrated that their approach also worked with other molecular catalysts based on different metals, suggesting the strategy could be used in a wider range of carbon dioxide conversion technologies.

To better understand why the system worked, the team combined laboratory experiments with advanced computer modeling. The researchers developed a time-dependent COMSOL model that simulated how protons, catalysts and reaction products moved throughout the electrochemical cell over time. The simulations revealed how acidity developed in different parts of the device, explaining why formic acid formed while unwanted hydrogen production remained limited.

“The computer modeling allowed us to visualize chemical processes that cannot be observed directly during the reaction,” said Pablo Fernandez, a Ph.D. student. “By tracking how acidity changed throughout the system, we could explain why this design favors formic acid production and use those insights to guide future improvements.”

Beyond explaining the experimental results, the modeling offers a roadmap for designing larger carbon dioxide electrolyzers that can better regulate acidity and improve efficiency. Pablo Fernandez said the work demonstrates that controlling large-scale acidity gradients could reshape how scientists design future electrochemical reactors.

“This research shows that managing acidity across an entire reaction system, not just at the catalyst surface, can fundamentally change what products are formed,” he said. “That opens new possibilities for converting carbon dioxide into valuable chemicals more efficiently while reducing waste.”