Interfacial regulation of the semiconductor heterostructure for enhanced photoelectrochemical and photocatalytic performances

•The band positions of the semiconductor crystals in nanoscale experience a significant shift when they are joined together.•The introduction of Au nanoparticles into the heterojunction interface instigates an additional band offset.•Compared to Si/ZnO array, Si/Au/ZnO array decreases resistance from 85 to 52 Ω and improves photocurrent from 0.5 to 4.0 µA for the superior band alignment.•The reaction rate of Si/Au/ZnO array is nearly twice that of Si/ZnO array and 2.53 times that of Si array.•The change of band position and band alignment by the interfacial regulation can be applied to other semiconductor heterostructures. The exotic performances of semiconductor heterostructures are generally ascribed to the band alignment and band bending at the heterojunction interface for the built-in potential. Herein, theoretic computations and experiments reveal for the first time that the band positions of Si and ZnO experience a significant shift when they are joined together. The introduction of Au nanoparticles into this interfacial layer matrix instigates an additional band offset, leading to the change from type-I to type-II band alignment. Compared to the binary architecture, the superior band alignment of the ternary architecture augments light absorption, concurrently suppressing photoluminescence and reducing resistance from 85 to 52 Ω. Moreover, a substantial improvement in photocurrent is achieved, increasing from 0.5 to 4.0 µA, alongside a significant elevation in photocatalytic activity from 1.90 × 10−3 to 3.67 × 10−3 min−1, indicating potential of the Si/Au/ZnO heterostructure as a promising candidate in optoelectronics and photocatalysis. The current work highlights the band offset and interfacial regulation of the semiconductor heterostructures, which diverges from the band bending for the built-in potential and can be extended to design heterogeneous semiconductor nanomaterials with suitable band alignment for their potential applications. Band offset and interfacial regulation of the core-shell Si/Au/ZnO nanowire array lead to the enhanced photoelectrochemical and photocatalytic performances. [Display omitted]