Theoretical Insight into the Trends that Guide the Electrochemical Reduction of Carbon Dioxide to Formic Acid

The electrochemical reduction (electroreduction) of CO₂ toformic acid (HCOOH) and its competing reactions, that is, theelectroreduction of CO₂ to CO and the hydrogen evolution reaction(HER), on twenty-seven different metal surfaces havebeen investigated using density functional theory (DFT) calculations.Owing to a strong linear correlation between the freeenergies of COOH* and H*, it seems highly unlikely that theelectroreduction of CO₂ to HCOOH via the COOH* intermediateoccurs without a large fraction of the current going to HER. On the other hand, the selective electroreduction of CO₂ to HCOOH seems plausible if the reaction occurs via the HCOO*intermediate, as there is little correlation between the free energies of HCOO* and H*. Lead and silver surfaces are found to be the most promising monometallic catalysts showing high faradaic efficiencies for the electroreduction of CO₂ to HCOOH with small overpotentials. Our methodology is widely applicable,not only to metal surfaces, but also to other classes of materialsenabling the computational search for electrocatalysts for CO₂ reduction to HCOOH.