Constructing Cascade Built‐In Electric Fields via Dual‐Epitaxial Heterointerfaces for Photocatalytic CO 2 ‐to‐C 2 H 4 Conversion

Constructing heterojunctions with built‐in electric fields (BIEFs) has emerged as an effective strategy to enhance charge separation in photocatalytic CO 2 reduction. However, the photocatalytic activity and C 2+ selectivity of current copper oxide‐based heterojunctions remain insufficient for practical applications, largely due to inefficient interfacial charge transport and limited C─C coupling efficiency. Herein, we report a 0D/1D CuO x /ZnO‐A400 photocatalyst featuring dual‐coherent Cu 2 O/CuO/ZnO heterointerfaces with cascade built‐in electric fields to realize a photocatalytic C 2 H 4 evolution rate of 12.7 µ mol h −1 (5 mg of catalyst) with a selectivity of 44.1%. Advanced electron microscopy combined with density functional theory calculations reveals the formation of atomically coherent Cu 2 O/CuO and CuO/ZnO interfaces. The directionally aligned BIEFs across the interfaces, pointing from Cu 2 O to CuO and from CuO to ZnO, establish a cascade charge‐transfer pathway that accelerates the separation and migration of photogenerated carriers, thereby promoting the C─C coupling of CO 2 molecules. This work provides an effective strategy for atomic‐scale interface engineering in multicomponent heterojunctions and offers new insights into the design of efficient photocatalytic systems for selective CO 2 conversion into value‐added multicarbon products.