Unveiling the high-activity origins of BiVO4-Zn tandems for CO2 photoreduction

Herein, we demonstrated the integration of BiVO₄-based photoanode with metallic Zn cathode for high-performance CO₂ reduction, and a record CO production rate of 113.32 μmol cm⁻² h⁻¹ with a FE_CO of 90.57 % has been achieved under simulated sunlight (AM 1.5 G, 100 mW), accompanying with an excellent stability. More importantly, the direct observation of spatial charge separation/transfer and dynamic surface catalysis for both H₂O oxidation and CO₂ reduction has been firstly achieved by the combination of in situ X-ray photoelectron spectroscopy (IS-XPS) with Fourier transform infrared reflection (IS-FTIR). Under light irradiation, the electron-hole pairs have been generated on BiVO₄ photoanode, and holes rapidly transfer to photoanode surfaces for participating in oxygen evolution reaction (OER) through the formation of *OH and *OOH intermediates. Simultaneously, the proton-coupled electron transfer to the Zn cathode surfaces drive the reduction of adsorbed CO₂ molecules into CO via the formation *COOH and *CO intermediates. Thereby, this work offers new insights into fundamental understanding of CO₂ reduction process, which facilitates the future development of highly efficient carbon fixation systems.