CO Hydrogenation Promoted by Oxygen Atoms Adsorbed onto Cu(100)

The electrochemical CO₂ reduction reaction (CO₂RR) on Cu-based catalysts is a promising method for converting anthropogenic CO₂ to valuable chemical feedstocks and fuels. Although pure CO₂ gas has been widely used as a reactant in CO₂RR-related research, CO₂ gas collected from the atmosphere inevitably includes some amount of various impurity gases in the actual application of this method. Among such impurities, O₂ gas has high reactivity and can easily contaminate the reaction environment, thereby substantially affecting the reactivity of the CO₂RR. Herein, we performed first-principles calculations for the CO₂RR in the presence of O₂ reduction reaction intermediates on the Cu(100) surface. Specifically, we calculated the reaction and activation free energies for the hydrogenation of adsorbed CO* to CHO* on a Cu(100) surface covered with O* or OH*. When the coverage of O* reached 25%, the initial state of CO hydrogenation became destabilized to a greater extent than the transition state, which decreased the reaction and activation free energies by 0.27 and 0.16 eV, respectively. The projected density of states analyses revealed that O* weakens the interaction between CO* and the Cu surface, whereas OH* less strongly affects CO hydrogenation.