Theoretical studies of CO oxidation with lattice oxygen on Co3O4 surfaces

Abstract

Low-temperature CO oxidation has attracted extensive interest in heterogeneous catalysis because of the potential applications in fuel cells, air cleaning, and automotive emission reduction. In the present study, theoretical investigations have been performed using density functional theory to elucidate the crystal plane effect and structure sensitivity of Co3O4 nano-catalysts toward catalyzing CO oxidation. It is shown that the surface Co–O ion pairs are the active site for CO oxidation on the Co3O4 surface. Because of stronger CO adsorption and easier removal of lattice oxygen ions, the Co3O4(011) surface is shown to be more reactive for CO oxidation than the Co3O4(001) surface, which is consistent with previous experimental results. By comparing the reaction pathways at different sites on each surface, we have further elucidated the nature of the crystal plane effect on Co3O4 surfaces and attributed the reactivity to the surface reducibility. Our results suggest that CO oxidation catalyzed by Co3O4 nanocrystals has a strong crystal plane effect and structure sensitivity. Lowering the vacancy formation energy of the oxide surface is key for high CO oxidation reactivity.