Enhanced photocatalytic activity of S-doped BiVO4 photocatalysts

Abstract

S-doped BiVO₄ photocatalysts were synthesized using a surfactant-free hydrothermal method without any further treatments and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), inductively coupled plasma atomic emission spectrometry (ICP-AES), ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), photoluminescence spectroscopy (PL) techniques, and transient photocurrent responses. The results show that S²⁻ ions can be doped into the BiVO₄ crystal lattices and substitute the O²⁻ ions, which can increase the BiVO₄ lattice parameters, increase the number of V⁴⁺ species and oxygen vacancies, and cause a red shift of the reflectance spectra. Compared with the pure BiVO₄ photocatalyst, S-doped BiVO₄ photocatalysts exhibit much higher photocatalytic activity in the degradation of methylene blue (MB) under visible light irradiation, because an appropriate amount of S²⁻ ions can improve the separation efficiency of photogenerated electron–hole pairs, and hinder their recombination. The photo-stability of the S-doped BiVO₄ photocatalysts, and the effects of the active species involved in the photocatalytic process from which we deduced a possible mechanism for MB photocatalytic degradation were also examined.