Effects of morphology on the visible-light-driven photocatalytic and bactericidal properties of BiVO4/CdS heterojunctions: A discussion on photocatalysis mechanism

BiVO 4 /CdS composites with different morphologies and mass ratios were successfully prepared via a facile deposition-precipitation method by adding different dispersants. Compared with spherical BiVO 4 (BS), sheet-like BiVO 4 nanoarrays (BA) showed higher (020) exposed areas, as confirmed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). X-ray photoelectron spectroscopy (XPS) revealed further details on the microstructure of the composites namely, CdS was deposited on the surface of BiVO 4 forming an S-(111) interface layer. The photocatalytic properties of the samples were tested by studying the degradation of Rhodamine B (RhB) and the sterilization of Escherichia coli ( E. coli ) under visible-light irradiation. The BAC-60 sample showed the best photocatalytic performance among all the catalysts owing to its: (i) improved high separation efficiency of the photo-induced charge carriers and (ii) high exposure activity of the (020) plane. Electrochemical tests with non-equilibrium carrier injection and free radical trapping experiments are introduced to analyze the mechanism, such as the effects of different crystal planes on the photocatalytic reaction and the flow direction of carriers at the CdS–BiVO 4 interface.