Disentangling Local Interfacial Confinement and Remote Spillover Effects in Oxide-Oxide Interactions

Supportedoxides are widely used in many important catalytic reactions,in which the interaction between the oxide catalyst and oxide supportis critical but still remains elusive. Here, we construct a chemicallybonded oxide-oxide interface by chemical deposition of Co3O4 onto ZnO powder (Co3O4/ZnO), in which complete reduction of Co3O4 to Co-0 has been strongly impeded. It was revealed thatthe local interfacial confinement effect between Co oxide and theZnO support helps to maintain a metastable CoO x state in CO2 hydrogenation reaction, producing93% CO. In contrast, a physically contacted oxide-oxide interfacewas formed by mechanically mixing Co3O4 andZnO powders (Co3O4-ZnO), in which reductionof Co3O4 to Co-0 was significantlypromoted, demonstrating a quick increase of CO2 conversionto 45% and a high selectivity toward CH4 (92%) in the CO2 hydrogenation reaction. This interface effect is ascribedto unusual remote spillover of dissociated hydrogen species from ZnOnanoparticles to the neighboring Co oxide nanoparticles. This workclearly illustrates the equally important but opposite local and remoteeffects at the oxide-oxide interfaces. The distinct oxide-oxideinteractions contribute to many diverse interface phenomena in oxide-oxidecatalytic systems.