Tandem catalysts CuSe/AuX for increasing local *CO concentration to promote the photocatalytic CO2 reduction to C2H4

It is highly desired yet challenging to strategically steer CO₂ reduction reaction (CO₂RR) toward ethylene (C₂H₄) with high activity under visible light irradiation. The key to achieving this goal is increasing the local *CO concentration on the catalyst surface and promoting the C-C coupling progress. Here, we prepare tandem catalysts of CuSe/Au_X to realize the photocatalytic reduction of CO₂ to C₂H₄ with high activity. Under light irradiation, the loaded Au NPs are used to activate and transfer CO₂ to *CO. The generated *CO intermediate could migrate to the surface of CuSe and cause the C-C coupling process. Moreover, the theoretical calculation results show that the transport process of *CO from Au NPs to CuSe is spontaneous, which plays a critical role in guaranteeing the high concentration of *CO intermediate on the surface of CuSe. This work not only reveals the effect of tandem catalysis on CO₂RR to C2 products but also explores the most suitable tandem catalyst to produce C₂H₄ with high activity by adjusting the loading amounts of Au NPs. Thus, it provides a way to adjust the Cu-based catalyst used in the production of C2 products by photocatalytic CO₂RR, which may attract extensive attention in the field.