Photocatalytic performance of AgS/ZnO/ZnS nanocomposites with high visible light response prepared via microwave-assisted hydrothermal two-step method.

A series of different ratios of AgS/ZnO/ZnS nanocomposites with visible light response were prepared by a microwave-assisted hydrothermal two-step method, whose composition, crystalline structure, morphology and surface physicochemical properties were well-characterized via X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (UV-vis/DRS), photoluminescence spectrum (PL), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and N adsorption-desorption measurements. Results showed that as-composites mainly consisted of ZnS crystal phase, whose grain size increased obviously compared with non AgS samples. At the same time, due to the introduction of narrow band gap AgS, the synthesized composite can effectively increase the visible optical absorption of ZnO/ZnS composites. Among them, 1% AgS/ZnO/ZnS showed a mixed structure of nano-line and nano-particle, of which BET value increased significantly, and the morphology was more excellent. Photocatalytic activities of a series of AgS/ZnO/ZnS composites under different light sources were studied using methyl orange as a model molecule, and 1% AgS/ZnO/ZnS was taken as the best one. Meanwhile, 1% AgS/ZnO/ZnS also showed a good degradation effect on other dyes with different structures, and its degradation efficiency did not change significantly after three cycles, showing certain stability. In addition, composites with AgS loading of 1% possessed the highest hydrogen production ability of photolysis water, indicating that the introduction of AgS had significantly enhanced the catalytic performance.