Highly Efficient Photocatalytic Degradation of Bisphenol A Under UV–Visible Light Irradiation Using Au/Zn3In2S6 Schottky Junction Photocatalyst

Designing and constructing heterojunctions has emerged as a pivotal strategy for improving the photocatalytic efficiency of semiconductors. In this study, we report the controlled synthesis of an Au/Zn3In2S6 Schottky junction through a combination of hydrothermal and in situ photodeposition methods. The structural, morphological, and photoelectrochemical properties of the catalyst were meticulously characterized using a suite of techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), photoelectrochemical (PEC) measurements, and electron spin resonance (ESR) spectroscopy. The optimized 3% Au/Zn3In2S6 composite exhibited a remarkable enhancement in both photocatalytic activity and stability, achieving a 90.4% removal of bisphenol A (BPA) under UV–visible light irradiation within 100 min. The corresponding first-order reaction rate constant was approximately 1.366 h−1, nearly 4.37 times greater than that of the pristine Zn3In2S6. This substantial improvement can be attributed to several key factors, including increased BPA adsorption, enhanced light absorption, and the efficient charge separation facilitated by the Au/Zn3In2S6 heterojunction. Photogenerated holes, superoxide radicals, and hydroxyl radicals were identified as the primary reactive species responsible for the BPA degradation. This work highlights the potential of metal-modified semiconductors for advanced photocatalytic applications, offering insights into the design of highly efficient materials for environmental remediation.