Facile Synthesis of a Z-Scheme ZnIn₂S₄/MoO₃ Heterojunction with Enhanced Photocatalytic Activity under Visible Light Irradiation

Employing a visible-light-driven direct Z-scheme photocatalytic system for the abatement of organic pollutants has become the key scientific approach in the area of photocatalysis. In this study, a highly efficient Z-scheme ZnIn₂S₄/MoO₃ heterojunction was prepared through the hydrothermal method, followed by the impregnation technique that facilitates the formation of an interface between the two phases for efficient photocatalysis. The structural, optical, and surface elemental composition and morphology of the prepared samples were characterized in detail through X-ray diffraction, UV-vis diffuse reflectance spectra, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The results indicate that the composite materials have a strong intimate contact between the two phases, which is beneficial for the effective separation of photoinduced charge carriers. The visible-light-mediated photocatalytic activity of the samples was tested by studying the degradation of methyl orange (MO), rhodamine B (RhB), and paracetamol in aqueous suspension. An optimum loading content of 40 wt % ZnIn₂S₄/MoO₃ exhibits the best degradation efficiency toward the above pollutants compared to bare MoO₃ and ZnIn₂S₄. The improved photocatalytic activity could be ascribed to the efficient light-harvesting property and prolonged charge separation ability of the Z-scheme ZnIn₂S₄/MoO₃ catalyst. Based on reactive species determination results, the Z-scheme charge transfer mechanism of ZnIn₂S₄/MoO₃ was discussed and proposed. This study paves the way toward the development of highly efficient direct Z-scheme structures for a multitude of applications.