Facile solvothermal synthesis of highly active monoclinic scheelite BiVO4 for photocatalytic degradation of methylene blue under white LED light irradiation

In this study, BiVO₄ was successfully synthesized via the solvothermal process using a solvent mixture of ethylene glycol and water under different synthesis conditions of temperature and pH. Physicochemical properties such as crystal phase, morphology, and optical absorption of the as-synthesized BiVO₄ samples were characterized by X-ray diffraction (XRD), Raman spectra, field emission scanning electron microscopy (FE-SEM), and ultraviolet–visible diffraction reflection spectroscopy (UV–vis DRS). The XRD analysis showed that different synthesis conditions of temperature and pH significantly affected the growth of monoclinic BiVO₄ crystals oriented along (0 4 0) facets. Form SEM results, the synthesis conditions, including pH and temperature, have a great effect on the morphology of monoclinic structured BiVO₄. As the pH value increases in the range of 0–9 and temperature increases from 80 °C to 180 °C, the morphology of BiVO₄ changed from peanut-, rod-, and leaf-like shapes. The photocatalytic activities of as-synthesized BiVO₄ photocatalysts were evaluated by the photodegradation of methylene blue (MB) dye under irradiation of white LED light. We have found that by using appropriate synthesis conditions (the synthesis temperature of 140 °C and the synthesis pH of 7) the BiVO₄ exhibited high photocatalytic efficiency for MB degradation (about 82.30% after 180 min of irradiation). This result is due to the development of the BiVO₄ crystals oriented along (0 4 0) facets with an increase in the intensity ratio of I_(0 4 0)/I_(1 2 1). The growth of BiVO₄ crystals oriented along (0 4 0) facets may be beneficial to enhance the photocatalytic activity of monoclinic scheelite BiVO₄.