Rational design of direct Z-scheme heterostructure NiCoP/ZIS for highly efficient photocatalytic hydrogen evolution under visible light irradiation

Construction of Z-scheme heterojunctions has been recognized as one of the most efficient strategies to significantly improve the charge-separation efficiency and achieve highly efficient solar energy conversion in photochemical reactions. Herein, a novel direct Z-scheme catalyst of NiCoP/ZIS was rational designed and prepared by dispersing ternary metal phosphide NiCoP in ZnIn2S4 (ZIS) nanoflowers under solvothermal method. The compact heterojunction structural characteristic of NiCoP/ZIS afford the composite prominent enhanced photocatalytic hydrogen (H2) production performance. The relative quantities of Ni and Co in NiCoP/ZIS composite can significantly influence the photocatalytic activities of the material, and the 37.5% Ni0.7Co0.3P/ZIS composite with a Ni/Co mole ratio of 0.7: 0.3 had the best hydrogen production efficiency with a hydrogen evolution rate of 3.84 mmol g−1h−1, which is approximately 8 times higher than that of single ZIS. The apparent quantum efficiency (AQE) for 37.5% Ni0.7Co0.3P/ZIS is about 5.14% under the incident monochromatic light of 405 nm. The subsequent electrochemical analyses proved the significant roles of the direct Z-scheme heterojunction in accumulating the electrons at the conduction bands of ZIS with more negative potential, which contributed to the stronger reduction activity in the promoted hydrogen generation for Ni0.7Co0.3P/ZIS. This work not only reported a a novel direct Z-scheme catalyst of NiCoP/ZIS heterostructure with enhanced photocatalytic hydrogen generation performance, but also provided a promising approach to rational design and construct efficient visible-light-driven photocatalysts for solar energy utilization.