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.