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

The electrocatalytic reduction of CO2 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 CO2 to CO on ZnO. Using in situ experimental techniques and quantum chemical calculations, we find that defects in ZnO promote the formation of Zn–ZnOx interfaces during CO2 reduction, which mediates an intimate-junction exciton state by the metal semiconductor heterophase. This promotes the formation of CO2 radicals, exposing electron donation centers for CO2 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 CO2.