Proton Turnover Dominated Cascade Route for CO2 Photoreduction

Abstract Photoreduction carbon dioxide (CO 2 ) and water (H 2 O) into valuable chemicals is a huge potential to mitigate immoderate CO 2 emissions and energy crisis. To date, tremendous attention is concentrated on the improvement of independent CO 2 reduction or H 2 O oxidation behaviors. However, the simultaneous control of efficient electron and hole utilization is still a huge challenge due to the complex cascade redox reactions. Here, a proton turnover exists in the whole CO 2 photoreduction process is discovered, which is defined as the pivot to concatenate the hole and electron behaviors. As a demonstration of the concept, the efficient activated hydrogen (*H) production centers of copper (Cu) and rapid hydrogenation centers of nickel (Ni) are coupled by an alloying strategy, and the proton turnover behaviors could be directly determined by adjustment of the molar ratios of Cu x Ni y . Moreover, Cu 3 Ni 1 –TiO 2 exhibits the highest electron selectivity of 93.7% for methane (CH 4 ) production with a rate of 175.9 µmol g −1 h −1 , while Cu 1 Ni 5 –TiO 2 reaches up to the highest carbon monoxide (CO) electron selectivity and generation rate at 84.4% and 164.6 µmol g −1 h −1 , respectively. Consequently, the experimental and theoretical analysis all clarify the predominate proton turnover effect during the overall CO 2 photoreduction process, which directly determines the categories and generated efficiency of C‐based products by regulating variable reaction pathways. Therefore, the revelation of the proton turnover pivot could broaden the new sights by bidirectional optimization of dynamics during the overall CO 2 photoreduction system, which favors the efficient, selective, and stable photocatalytic CO 2 reduction with H 2 O.