Z-scheme CdS–Au–BiVO4 with enhanced photocatalytic activity for organic contaminant decomposition

Abstract

A Z-scheme heterogeneous photocatalyst CdS–Au–BiVO₄ was synthesized for the first time by photo-reduction and deposition–precipitation methods. The microstructures and optical properties of the as-prepared samples were investigated by means of scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectroscopy (DRS). Due to the oriented accumulation of electrons on the {010} facets of BiVO₄ crystals, Au nanoparticles were successfully anchored on the {010} facets of BiVO₄ crystals via the photo-reduction process. CdS was further selectively deposited on the surface of Au nanoparticles, benefitting from the strong S–Au interaction. Photocatalytic degradations of tetracycline and Rhodamine B indicated that CdS–Au–BiVO₄ exhibits much higher photocatalytic activity than BiVO₄, Au–BiVO₄, and CdS–BiVO₄. Radical trapping experiments confirmed that in the case of CdS–Au–BiVO₄, the main reactive species responsible for organic contaminant degradation are h⁺, ˙OH, and ˙O₂⁻, while only h⁺ can be produced in the case of CdS–BiVO₄. Based on the photoelectrochemical analysis and radical trapping experiments, it can be deduced that the Z-scheme structure of CdS–Au–BiVO₄ not only decreases the recombination rate of photo-generated carriers but also makes the holes and electrons keep a higher redox ability.