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

Abstract

• Direct Z-scheme catalyst of NiCoP/ZIS was prepared through hydrothermal method. • The 37.5% Ni 0.7 Co 0.3 P/ZnIn 2 S 4 showed the best H 2 evolution rate of 3.84 mmol g −1 h −1 . • The charge transfer pathway of NiCoP/ZIS followed the Z-scheme mechanism. 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 ZnIn 2 S 4 (ZIS) nanoflowers under solvothermal method. The compact heterojunction structural characteristic of NiCoP/ZIS afford the composite prominent enhanced photocatalytic hydrogen (H 2 ) 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% Ni 0.7 Co 0.3 P/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 −1 h −1 , which is approximately 8 times higher than that of single ZIS. The apparent quantum efficiency (AQE) for 37.5% Ni 0.7 Co 0.3 P/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 Ni 0.7 Co 0.3 P/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.