Construction of Z-scheme heterojunction interfacial charge transfer pathways in ZnIn2S4@NENU-5 for photocatalytic hydrogen evolution

Abstract

Utilizing the design of heterojunction structures formed between photocatalysts to enhance photoelectrochemical performance represents an effective strategy for improving the efficiency of photocatalytic hydrogen production. In this work, a straightforward one-step solvothermal method was employed to embed NENU-5 nano-octahedra within ZnIn₂S₄ nanoflowers, forming ZnIn₂S₄@NENU-5 heterostructures. Hydrogen production tests conducted over 5 h revealed a hydrogen evolution activity of 5282.14 μmol g⁻¹ h⁻¹ in triethanolamine (TEOA) solution at pH = 9, which is 4.9 times and 264 times higher than that of pure ZnIn₂S₄ and NENU-5, respectively. The significant enhancement in the photocatalytic performance indicates that the constructed Z-scheme heterojunction increases the active sites on the catalyst surface and plays a crucial role in photocarrier transfer. Furthermore, the formation of the Z-scheme heterojunction is confirmed through Mott–Schottky (M–S) analysis, ultraviolet photoelectron spectroscopy (UPS), and valence band X-ray photoelectron spectroscopy (VB-XPS). The effective charge transfer at the ZnIn₂S₄@NENU-5 heterojunction interface is validated based on X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) analysis, and density functional theory (DFT) calculations. In summary, this work offers an effective approach to designing novel heterojunction photocatalysts by combining MOF materials with bimetallic sulfides, thereby promoting the efficiency of photocatalytic hydrogen production.