CdS QDs modified three-dimensional ordered hollow spherical ZnTiO3-ZnO-TiO2 composite with improved photocatalytic performance

Three-dimensional ordered hollow spherical ZnTiO3-ZnO-TiO2 composite (3DOH ZnTiO3-ZnO-TiO2) was prepared by vacuum impregnation combined with calcination method using polystyrene (PS) colloidal microspheres as the template, and the CdS QDs were modified into 3DOH ZnTiO3-ZnO-TiO2 by water bath method. The crystal structure, chemical composition, surface morphology, optical absorption and surface physicochemical properties of CdS QDs modified 3DOH ZnTiO3-ZnO-TiO2 (CdS QDs 3DOH ZnTiO3-ZnO-TiO2) composite were well characterized. The results show that the three-dimensional ordered hollow spherical CdS QDs 3DOH ZnTiO3-ZnO-TiO2 composite mainly composes of anatase phase TiO2, rutile phase TiO2, and hexagonal phase ZnTiO3 and hexagonal phase ZnO. Among them, a homojunction is formed between the mixed crystal phase of TiO2 (anatase–rutile), and a heterojunction is found between hexagonal phase ZnTiO3 and hexagonal phase ZnO. In addition, the composite treated by the polystyrene (PS) colloidal microspheres template has formed the three-dimensional ordered hollow sphere structure, the hollow spheres are arranged neatly and orderly, and the sphere wall is formed by stacking nanoparticles. At the same time, the three-dimensional ordered hollow spherical structure of CdS QDs 3DOH ZnTiO3-ZnO-TiO2 composite provides more transfer paths for material transport and promotes repeated light absorption, prolonging the lifetime of photogenerated charge carriers. Moreover, due to the close connection between CdS QDs, ZnTiO3, ZnO and TiO2, the separation of electrons and hole pairs is facilitated, and the recombination of electron and hole pairs is effectively suppressed, so that CdS QDs 3DOH ZnTiO3-ZnO-TiO2 composite exhibits extremely high photocatalytic activity. Its hydrogen production is more than 300 times that of pure TiO2, moreover, of which cycle stability also shows better.