Two-dimensional Janus heterostructures for superior Z-scheme photocatalytic water splitting

Abstract

Abstract Developing robust water splitting photocatalyst remains a pivot challenge for solar-to-fuel conversion. Herein, two-dimensional (2D) Janus bilayer heterostructures are reported by sulfur-vacancy-confined-in ZnIn2S4 (Vs-ZnIn2S4) and WO3 nanosheets as an all-solid-state Z-scheme prototype. First-principle calculations and experimental observations clearly confirm the spontaneous formation of this redox-mediator-free Z-scheme van der Waals heterostructure at atomic level, not only facilitating the space separation of photoexcited carriers with high charge density, enhancing charge dynamics and optimizing charge lifetime, but also accumulating electrons in conduction band of Vs-ZnIn2S4 and holes in valence band of WO3 by internal electric field through W–S bonds. After integrated by NiS quantum dots, novel 2D/2D NiS/Vs-ZnIn2S4/WO3 heterostructures with high stability exhibited an outstanding visible-light hydrogen evolution rate of 11.09 mmol g−1 h−1 and an apparent quantum efficiency about 72% at 420 nm, the highest value so far reported among the family of ZnIn2S4 photocatalysts. This work not only presents novel Janus heterostructures but also paves the atomic-level structural and interfacial design and the construction of 2D Janus bilayer Z-scheme heterojunctions for solar energy conversion applications.