Reaction Mechanisms of the Electrochemical Conversion of Carbon Dioxide to Formic Acid on Tin Oxide Electrodes

Recent reports on the electrochemical production of formate demonstrate that reduced metal oxides play a key role in activating stable CO2 molecules. To expand a pre-existing design principle of catalysts to a higher level, one of the remaining issues is to clearly understand the reaction mechanism. In recent years, mechanistic studies on SnOx catalysts, one of the most popular candidates for CO2 conversion to formate, have been intensively conducted in various aspects. In this Minireview, we summarize the reaction mechanisms of formate production based on computational, electrokinetic and in situ analyses focusing on SnOx catalysts. Starting from theoretical points including key intermediates, reaction pathway, and selectivity for formate production over pure metals, the discussion is expanded to the reaction mechanism on oxide surface.