Synthesis of BiVO4via oxidant peroxo-method: insights into the photocatalytic performance and degradation mechanism of pollutants

Abstract

This paper reports the synthesis of monoclinic bismuth vanadate (BiVO₄) by the oxidant peroxide method with crystallization under hydrothermal conditions, and its catalytic performance on the photodegradation of pollutants under visible light. The as-synthesized BiVO₄ materials were characterized by means of X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), Raman spectroscopy, Ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS) and scanning electron microscopy (SEM). Hydrothermal treatment above 80 °C was required to obtain pure monoclinic BiVO₄ phase by releasing V⁵⁺ ions from vanadium peroxo complexes. With the increase in hydrothermal reaction temperature, the particle size decreased. All BiVO₄ samples presented large size and shape distribution and band gap of approximately 2.40 eV. The as-prepared BiVO₄ catalysts showed high photoactivity for decomposition of model pollutants, methylene blue (MB) and rhodamine B (RhB) dyes, under exposure to visible light. The photodegradation mechanism was evaluated by adding scavengers, DMSO and KBrO₃, which were used to probe ˙OH radical and conduction band (CB) electrons, respectively. It was observed that photodegradation of MB and RhB dyes is caused by the action of ˙OH radicals, and that BiVO₄ CB electrons do not have reduction potential sufficiently high to reduce dissolved oxygen to O₂⁻˙. It was proven that the indirect mechanism, i.e. ˙OH radical formation, plays the major role on the BiVO₄-assisted photodegradation process.