Effects of pH on the microstructure and surface charge of BiVO4 prepared via hydrothermal method: formation mechanism and photocatalytic performance

A simple and feasible hydrothermal method was employed to regulate the surface charge and growth degree of active facet of BiVO4 by varying the pH value of precursor. The prepared products were characterized by XRD, Raman spectra, SEM, N-2 adsorption and desorption, zeta potential, and UV-Vis DRS. It is found that with increasing the pH value, not only do the phase composition, micro-morphology, specific surface area, and light absorption of BiVO4 products have obvious changes, but so do the surface charge and growth degree of {010} facet. A possible formation mechanism is proposed on the basis of the characterization results. The photocatalytic activities were evaluated by the degradation of rhodamine B solution under visible light irradiation. The results showed that monoclinic scheelite BiVO4 (m-BiVO4) particles prepared at pH 4 exhibit the maximum adsorption capacity and the best photocatalytic performance, which was mainly attributed to the negatively charged surface. On the contrary, the similar degradation rate and kinetic constant of the m-BiVO4 prepared at pH 3 could be ascribed to the preferential growth of {010} facets.