Unique NiCo₂S₄@ZnS/CdS Yolk–Shell\nHeterojunction for Efficient Visible-Light-Driven Photocatalytic Water\nSplitting

Abstract

Construction\nof rational heterojunction nanostructures is an effective\napproach to enhance photocatalytic performance of semiconductor photocatalysts\nfor solar-driven hydrogen production from water splitting. Herein,\na unique non-noble-metal hollow heterostructure NiCo₂S₄@ZnS/CdS assembled by a ZnS/CdS light absorber with tunable\ncompositions and a yolk–shell NiCo₂S₄ cocatalyst was constructed for the first time. Interestingly, the\nyolk–shell NiCo₂S₄ microspheres have\na uniform size, and the composition of the ZnS/CdS coating layer can\nbe tuned via adjusting the cation-exchange reaction time. Remarkably,\nsuch hollow NiCo₂S₄@ZnS/CdS yolk–shell\nheterostructures displayed enhanced H₂ evolution reaction\n(HER) activity of 20.17 mmol·g^–1·h^–1 under visible-light (λ > 420 nm) irradiation,\napproximately 14.4- and 5.6-fold that of ZnS/CdS and 3 wt % Pt-loaded\nZnS/CdS, respectively. Moreover, the NiCo₂S₄@ZnS/CdS hybrids owned favorable photocatalytic stability as confirmed\nby the cycling and long-term H₂ evolution tests. The excellent\nphotocatalytic capacity of NiCo₂S₄@ZnS/CdS can\nbe ascribed to the heightened light absorption enabled by the yolk–shell\narchitecture, efficient charge transfer and separation by the interfacial\nheterojunctions, as well as numerous active sites from the NiCo₂S₄ cocatalyst. The findings presented here could\nenlighten the rational structural regulation of semiconductor nanomaterials\nto promote solar conversion and utilization.