Origin of the Selective Electroreduction of Carbon Dioxide to Formate by Chalcogen Modified Copper

The electrochemical reduction of atmospheric CO₂ by renewable electricity opens new routes to synthesize fuels and chemicals, but more selective and efficient catalysts are needed. Herein, by combining experimental and first-principles studies, we explain why chalcogen modified copper catalysts are selective toward formate as the only carbon product. On the unmodified copper, adsorbed CO₂ is the key intermediate, yielding carbon monoxide and formate as carbon products. On sulfur, selenium, or tellurium modified copper, chalcogen adatoms are present on the surface and actively participate in the reaction, either by transferring a hydride or by tethering CO₂ thus suppressing the formation of CO. These results highlight the active role of chalcogen centers via chemical steps and point toward basicity as the key descriptor for the stability and selectivity of these catalysts.