Constructing Cascade Built-In Electric Fields via Dual-Epitaxial Heterointerfaces for Photocatalytic CO2-to-C2H4 Conversion.

Constructing heterojunctions with built-in electric fields (BIEFs) has emerged as an effective strategy to enhance charge separation in photocatalytic CO2 reduction. However, the photocatalytic activity and C2+ 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 CuOx/ZnO-A400 photocatalyst featuring dual-coherent Cu2O/CuO/ZnO heterointerfaces with cascade built-in electric fields to realize a photocatalytic C2H4 evolution rate of 12.7 µmol 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 Cu2O/CuO and CuO/ZnO interfaces. The directionally aligned BIEFs across the interfaces, pointing from Cu2O 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 CO2 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 CO2 conversion into value-added multicarbon products.