Rational design of MoS2/g-C3N4/ZnIn2S4 hierarchical heterostructures with efficient charge transfer for significantly enhanced photocatalytic H2 production

Abstract

The rational design of hierarchical heterojunction photocatalysts with efficient spatial charge separation remains an intense challenge in hydrogen generation from photocatalytic water splitting. Herein, a noble-metal-free MoS2/g-C3N4/ZnIn2S4 ternary heterostructure with a hierarchical flower-like architecture was developed by in situ growth of 3D flower-like ZnIn2S4 nanospheres on 2D MoS2 and 2D g-C3N4 nanosheets. Benefiting from the favorable 2D-2D-3D hierarchical heterojunction structure, the resultant MoS2/g-C3N4/ZnIn2S4 nanocomposite loaded with 3 wt% g-C3N4 and 1.5 wt% MoS2 displayed the optimal hydrogen evolution activity (6291 μmol g−1 h−1), which was a 6.96-fold and 2.54-fold enhancement compared to bare ZnIn2S4 and binary g-C3N4/ZnIn2S4, respectively. Structural characterizations reveal that the significantly boosted photoactivity is closely associated with the multichannel charge transfer among ZnIn2S4, MoS2, and g-C3N4 components with suitable band-edge alignments in the composites, where the photogenerated electrons migrate from g-C3N4 to ZnIn2S4 and MoS2 through the intimate heterojunction interfaces, thus enabling efficient electron-hole separation and high photoactivity for hydrogen evolution. In addition, the introduction of MoS2 nanosheets highly benefits the improved light-harvesting capacity and the reduced H2-evolution overpotential, further promoting the photocatalytic H2-evolution performance. Moreover, the MoS2/g-C3N4/ZnIn2S4 ternary heterostructure possesses prominent stability during the photoreaction process owing to the migration of photoinduced holes from ZnIn2S4 to g-C3N4, which is deemed to be central to practical applications in solar hydrogen production.