Synthesis of ZnS@CdS–Te composites with p–n heterostructures for enhanced photocatalytic hydrogen production by microwave-assisted hydrothermal method

Abstract

In this paper, ZnS@CdS–Te composites with visible light response were successfully prepared by microwave-assisted hydrothermal method. X-ray diffraction(XRD), UV–vis diffuse reflectance spectroscopy (UV–vis/DRS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy–energy dispersive spectrometer (SEM–EDS), high-resolution transmission electron microscopy (HR-TEM), and N2 adsorption–desorption measurements were utilized to test the structure, composition, morphology, surface physical and chemical properties, and optical absorption properties of ZnS@CdS–Te. The results show that the composites consist of hexagonal Te, hexagonal CdS, and cubic ZnS. Compared with CdS–Te, the crystallinity of ZnS@CdS–Te is significantly improved. The composites introduce ZnS, which inhibites the growth of (110) crystal plane of CdS. In addition, the obtained products have uniform size and the shape of the string structure. Furthermore, the crystallite size, specific surface area, and pore volume have a significant increase after recombination. Using malachite green (MG) as the model molecule, a series of photocatalysts degradation of MG was studied and compared. The results of photocatalytic degradation show that the synthesized ZnS@CdS–Te composites own favourable photocatalytic performance under ultraviolet light, visible light, and simulated sunlight. Moreover, compared with the monomer, ZnS@CdS–Te composites exhibit excellent hydrogen production capacity (592.5 μmol g−1 h−1), which is 48.4 times larger than the activity of commercial P25. Besides that, ZnS@CdS–Te composites could maintain high hydrolysis capacity of hydrogen after four cycles, proving that the composites have certain stability.