Boosting the activity and stability of Ag-Cu2O/ZnO nanorods for photocatalytic CO2 reduction

To construct semiconductor-based photocatalysts for carbon dioxide (CO2) reduction with high activity and stability remains a long-term goal. Herein, we report a ternary Ag-Cu2O/ZnO nanorods (NRs) hybrid catalyst with efficient charge carrier separation/transfer and CO2 adsorption capacity, which demonstrates much improved activity in comparison with bare ZnO NRs for photocatalytic CO2 reduction to carbon monoxide (CO) under UV–vis light. Mechanistic studies reveal that the deposited Cu2O enhances the CO2 chemisorption on the surface of catalysts and the formation of Z-scheme system between Cu2O and ZnO facilitates the photogenerated charge separation. The subsequent assembly of Ag nanoparticles (NPs) onto Cu2O is able to further promote the transfer of electrons due to the “electron sink” effect of Ag, which leads to the higher photocatalytic activity. As such, the synergy effect of strong CO2 chemisorption and multiple electrons transfer results in the boosted photocatalytic activity of Ag-Cu2O/ZnO NRs for CO2 reduction. In addition, compared with the binary Cu2O/ZnO NRs, the activity of Ag-Cu2O/ZnO NRs can be well maintained after multiple-cycle reaction. The possible reason is that the deposited Ag can alleviate the self-photoreduction of Cu2O by transferring the excess electrons accumulated in the conduction band (CB) of Cu2O, thus preserving the stability of the Ag-Cu2O/ZnO NRs photocatalyst.