Preparation of MoS2/CuS Heterojunction and Its Photocatalytic Degradation of Malachite Green

Copper sulfide (CuS), molybdenum disulfide (MoS2) monomers, and MoS2/CuS heterojunction photocatalysts with MoS2 molar fractions of 5%, 10%, 15%, and 20% were prepared via a hydrothermal method. The synthesis of MoS2/CuS heterojunctions was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis-DRS), electrochemical impedance spectroscopy (EIS), Mott-Schottky (MS) measurements, and other techniques. Their degradation performance towards malachite green (MG) was evaluated. Compared with pure CuS and MoS2, the 20% MoS2/CuS catalyst exhibited the optimal activity, achieving a degradation rate of 93.66% for MG under xenon lamp irradiation for 4 hours. Combined with the characterization results of XPS, MS, and ultraviolet photoelectron spectroscopy (UPS), it was confirmed that electrons transfer from CuS to MoS2 in the heterojunction, following a Z-scheme charge transfer mechanism. Radical quenching experiments revealed that superoxide radicals (·O2−) and holes (h+) are the main active species in the MoS2/CuS system, with ·O2− playing a dominant role in the photocatalytic degradation of MG. By constructing a MoS2/CuS heterojunction, an efficient Z-scheme photocatalytic system was successfully realized, proposing a practical approach to the design and band engineering of composite photocatalysts.