Characterization and photocatalytic properties of N-doped BiVO4 synthesized via a sol-gel method

A N-doped BiVO4 photocatalyst with high visible light activity was synthesized by the complexing sol-gel method using citric acid as a chelate and hexamethylene tetramine (C6H12N4) as a nitrogen source. The as-prepared N-doped BiVO4 samples were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), specific surface area (BET) and UV-Vis diffuse reflectance spectroscopy (DRS). The photocatalytic activity was evaluated by photocatalytic degradation of methyl orange (MO) solution under visible light. This technique revealed that pure BiVO4 and all the N-doped samples were in a monoclinic phase; no peaks of any other phases or impurities were detected. Nitrogen atoms were doped into the BiVO4 lattice and filled the atomic sites of oxygen to form O-Bi-N-V-O bonds, which contributed to the appearance of the more active species V4+ and oxygen vacancies. The doped nitrogen resulted in a red shift in the absorption edge. However, the N-doping only slightly changed the morphologies and BET special surface areas of the samples. The photocatalytic activity of BiVO4 significantly depended on the N-doping content and the calcination temperature. The maximum activity was observed for the catalyst obtained via calcination at 500 degrees C, for which the molar ratio of N to Bi was 0.20. Excess N-doping decreased the light absorption. (c) 2012 Elsevier B. V. All rights reserved.