Photoelectrochemical performance enhancement of ZnO photoanodes from ZnIn2S4 nanosheets coating

Developing photoanodes with high light-harvesting efficiency and great electronic transmission capacity remains a key challenge in photoelectrochemical (PEC) water splitting. In this paper, we reported an effective approach to enhance the PEC performance of ZnO nanowire arrays (NAs) photoanodes via overcoating ZnIn2S4 nanosheets onto the ZnO surfaces. The ZnIn2S4 electrocatalyst nanosheets were grown on the reduced graphene oxide (RGO) substrates by solvothermal synthesis and then grafted onto ZnO NAs, forming ZnO NAs/RGO/ZnIn2S4 heterojunctions. The ZnIn2S4 shells acted as visible light sensitizers, and the type-II band alignment between the ZnIn2S4 shells and the ZnO cores contributed to charge separation and transport. Meanwhile, the introduction of RGO nanosheets largely increased the surface area and accelerated the PEC process by reducing the energy barrier of interfacial electrochemical reaction. As a result, over 200% enhancement of photo-to-hydrogen conversion efficiency was achieved from the ZnO NAs/RGO/ZnIn2S4 heterojunctions compared to bare ZnO NAs. The results demonstrate that the RGO-based core/shell heterojunction arrays can provide a facile and compatible configuration for the potential applications in solar water splitting.