Understanding of C=O bonding activation during CO2 electroreduction: A case study of CO2 reduction to CO on ZnO

Summary The electrocatalytic reduction of CO 2 is an attractive method for reducing greenhouse gases and producing chemical feedstocks. However, the activation of C=O bonds limits the reaction kinetics; therefore, understanding the mechanism of C=O bond activation can guide the design of high-performance catalysts. Here, we investigate the C=O bond activation mechanism during the electroreduction of CO 2 to CO on ZnO. Using in situ experimental techniques and quantum chemical calculations , we find that defects in ZnO promote the formation of Zn–ZnO x interfaces during CO 2 reduction, which mediates an intimate-junction exciton state by the metal semiconductor heterophase. This promotes the formation of CO 2 radicals, exposing electron donation centers for CO 2 adsorption and redox centers for cleaving stable C=O bonds. The internal electric field generated by the heterojunction enhances the initial C=O activation by facilitating the interaction between the metalized Zn d-orbital and the O π -orbital in CO 2 .