Enhanced Photocarrier Separation in Hierarchical Graphitic-C₃N₄-Supported CuInS₂ for Noble-Metal-Free Z-Scheme Photocatalytic Water Splitting

The effective separation of photogenerated electrons and holes in photocatalysts is a prerequisite for efficient photocatalytic water splitting. CuInS₂ (CIS) is a widely used light absorber that works properly in photovoltaics but only shows limited performance in solar-driven hydrogen evolution due to its intrinsically severe charge recombination. Here, we prepare hierarchical graphitic C₃N₄-supported CuInS₂ (denoted as GsC) by an in situ growth of CIS directly on exfoliated thin graphitic C₃N₄ nanosheets (g-C₃N₄ NS) and demonstrate efficient separation of photoinduced charge carriers in the GsC by forming the Z-scheme system for the first time in CIS-catalyzed water splitting. Under visible light illumination, the GsC features an enhanced hydrogen evolution rate up to 1290 μmol g^-1 h^-1, which is 3.3 and 6.1 times higher than that of g-C₃N₄ NS and bare-CIS, respectively, thus setting a new performance benchmark for CIS-based water-splitting photocatalysts.