Modification of BiOI Microplates with CdS QDs for Enhancing Stability, Optical Property, Electronic Behavior toward Rhodamine B Decolorization, and Photocatalytic Hydrogen Evolution

Fast recombination of photoinduced charge carriers is a major problem in the case of semiconductor based photocatalysts, which must be solved for their potential application in photocatalysis. In this work, photostable CdS QDs/BiOI composites have been successfully fabricated by a two-step precipitation–deposition method. The prepared samples were characterized by X-ray diffraction (XRD), UV–vis diffuse reflection spectroscopy (UV–vis DRS), photoluminescence (PL) spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Mott–Schottky, and electrochemical impedance analysis. The potential applications of CdS QDs/BiOI composite materials have been tested toward decolorization of rhodamine B (RhB) solution and hydrogen generation under solar light and visible light irradiation, respectively. It has been observed that hydroxyl radicals, electrons, and holes played a major role in decolorization of RhB solution. Among all prepared photocatalysts, 4% CdS QDs/BiOI composite was able to decolorize 82% of RhB solution in 1 h and 203 μmol/h of H<sub>2</sub> under solar light and visible light irradiation, respectively. The highest activity has been ascribed to optimal loading of CdS QDs, good formation of composites, and the lowest recombination of charge carriers.