Composite of g-C3N4/ZnIn2S4 for efficient adsorption and visible light photocatalytic reduction of Cr(VI)

In this paper, the g-C3N4/ZnIn2S4 composite was synthesized by a two-stage hydrothermal method. The microstructure, surface, and optical properties of the composite were thoroughly characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) surface area analysis, and UV-Vis absorption spectroscopic analysis. The removal capacity of Cr(VI) was optimized by using ZnIn2S4 loaded in the composite. Meanwhile, the optimal pH environment for the reduction of Cr(VI) was determined to be about pH 3, and the reduction efficiency could reach more than 99% within 60 min. Further, the results of UV-Vis absorption analysis indicated the high and wide range of light absorption by composite compared with pure g-C3N4. Therefore, the enhanced photocatalytic performance of the composite could be attributed to the well-matched energy band structure between g-C3N4 and ZnIn2S4, which apparently promoted the effective separation and transfer of photogenerated carriers. In addition, the composite showed good stability in the visible light catalytic reaction, and the possible mechanism of the photocatalytic activity of Cr(VI) reduction by the composite was proposed.