After 150 years, a breakthrough in understanding the conversion of CO2 to electrofuels

Scientists have long sought ways to convert abundant CO2 to useful products such as chemicals and fuel. As early as in 1869, they were able to electrocatalytically convert CO2 to formic acid. Over the past two decades, the rise of CO2 in the Earth's atmosphere has significantly accelerated research in CO2 conversion using renewable energy resources, including solar, wind, and tidal. Because these resources are intermittent—the sun doesn't shine every day, nor does the wind constantly blow—how to store renewable energy safely and cost-effectively is a major challenge.

Recent research in electrocatalytic CO2 conversion points the way to using CO2 as a feedstock and renewable electricity as an energy supply for the synthesis of different types of fuel and value-added chemicals such as ethylene, ethanol, and propane. But scientists still do not understand even the first step of these reactions—CO2 activation, or the transformation of the linear CO2 molecule at the catalyst surface upon accepting the first electron. Knowing the exact structure of the activated CO2 is essential because its structure dictates both the end product of the reaction and its energy cost. This reaction can start from many initial steps and go through many pathways, giving typically a mixture of products. If scientists figure out how the process works, they will be better able to selectively promote or inhibit certain pathways, which will lead to the development of a commercially viable catalyst for this technology.

Columbia Engineering researchers announced today that they solved the first piece of the puzzle—they have proved that CO2electroreduction begins with one common intermediate, not two as was commonly thought. They applied a comprehensive suite of experimental and theoretical methods to identify the structure of the first intermediate of CO2 electroreduction: carboxylate CO2—that is attached to the surface with C and O atoms. Their breakthrough, published online today in PNAS, came by applying surface enhanced Raman scattering (SERS) instead of the more frequently used surface enhanced infrared spectroscopy (SEIRAS). The spectroscopic results were corroborated by quantum chemical modeling.

"Our findings about CO2 activation will open the door to an incredibly broad range of possibilities: if we can fully understand CO2electroreduction, we'll be able to reduce our dependence on fossil fuels, contributing to the mitigation of climate change," says the paper's lead author Irina Chernyshova, associate research scientist, department of earth and environmental engineering. "In addition, our insight into CO2 activation at the solid-water interface will enable researchers to better model the prebiotic scenarios from CO2 to complex organic molecules that may have led to the origin of life on our planet."