2D MPX₃-Based Noble-Metal-Free NiPS₃/ZnIn₂S₄ Heterojunction Catalyst for Enhanced Photocatalytic Hydrogen Evolution

Two-dimensional (2D) MPX 3 (X = S, Se) materials possess an abundance of catalytically active sites, making them promising candidates for efficient catalysis. In this study, NiPS 3 -loaded ZnIn 2 S 4 (NPS/ZIS) heterostructures were synthesized. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) confirmed the formation of a tightly integrated heterojunction between NPS and ZIS. Diffuse reflectance spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS) observations indicate that ZIS and NPS form a type I heterojunction. Furthermore, density functional theory (DFT) calculations reveal the presence of a built-in electric field from ZIS to NPS, facilitating effective electron transfer. Meanwhile, NPS functions as an efficient reductive cocatalyst, lowering the energy barrier for hydrogen evolution and thereby enhancing reaction efficiency. Photocatalytic experiments revealed that the introduction of NPS significantly promotes the photocatalytic hydrogen evolution under visible light irradiation (>420 nm). Specifically, the photocatalytic hydrogen evolution rate of the 2-NPS/ZIS heterostructure (containing 5.0 wt % NPS) reaches 7.8 mmol·g –1 ·h –1, which is 7.0 times higher than that of pristine ZIS and significantly exceeds the activity of traditional noble-metal cocatalyst Pt-loaded ZIS. Cycling tests showed that 2-NPS/ZIS remained stable during photocatalytic hydrogen evolution reaction (HER), with no significant decay in HER activity over an 18 h reaction period. This study provides valuable insights and approaches for the development of low-cost, high-efficiency photocatalysts for photocatalytic hydrogen production.