Tuning activity and selectivity of CO2 hydrogenation via metal-oxide interfaces over ZnO-supported metal catalysts

Abstract

Metal-oxide interface is generally regarded as the active sites in CO2 hydrogenation while their structure–property relationships are hardly identified. Herein, ZnO-supported Ru (Ru/ZnO) and Ni (Ni/ZnO) catalysts were used for CO2 hydrogenation. Their interfacial structures were finely tuned by altering the nature of supported metal particles and the support morphology, which significantly affect the catalytic activity and product selectivity. Direct evidences indicate that the weak basic sites are responsible for catalytic activity. The catalytic reaction proceeds through the dissociation mechanism involving the key intermediate of adsorbed CO species, whose strength determines product selectivity. A weak CO adsorption capacity on Ni species leads to high CO selectivity on Ni/ZnO catalysts, while CH4 could be produced on Ru/ZnO catalysts with strong CO binding capacity on low-coordination Ru species. Consequently, more low-coordination Ru species presented on Ru/p-ZnO (nanoplates) induced by stronger metal-support interactions contribute to a higher CH4 selectivity. These results deepen the understanding of metal-oxide interface in CO2 hydrogenation and broaden the concept of morphology-dependent catalysis of oxide-based catalysts.