Involving CeVO4 in improving the photocatalytic activity of a Bi2WO6/allophane composite for the degradation of gaseous acetaldehyde under visible light

Abstract

Indoor air quality is affected by hazardous chemical substances emitted from buildings, construction and decoration materials, indoor equipments or even due to human activities. In this study, the hydrothermal synthesis and mechanical mixing were applied to synthesize Bi2WO6/CeVO4/allophane composites (BW/CV/A), and their photocatalytic performance for the degradation of acetaldehyde, as a common indoor air pollutant, was evaluated under visible-light irradiation. The as-prepared composites were characterized by X-ray diffraction (XRD), Raman spectroscopy, high-resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), and UV–visible (UV–vis) spectroscopy. The results demonstrated that the prepared composites had microstructures consisting of nanosheets of hierarchical flower-like Bi2WO6 microspheres on which the CeVO4 nanocrystals were fully embedded in the presence of allophane nanoparticles. The specific surface areas of the as-synthesized and mechanically mixed BW1/CV1/A composites were in the range of 110–182m2g−1. The effect of the amount of CeVO4 on photocatalytic activity of the Bi2WO6/allophane composite was explored, and the highest photocatalytic activity was observed for the BW1/CV1/A composite (Bi2WO6:CeVO4=1:1 mass ratio). Compared with the Bi2WO6/allophane and CeVO4/allophane composites, the hydrothermally synthesized BW1/CV1/A composite showed a significantly higher photocatalytic activity for the degradation of acetaldehyde under visible-light irradiation. The enhancement in the photocatalytic activity of the Bi2WO6/allophane composite achieved by involving the CeVO4 nanocrystals is due presumably to an extended light absorption range, appropriate band structures of Bi2WO6 and CeVO4, the formed p–n heterojunction, and the co-existence of Ce3+ and Ce4+ in CeVO4, resulting in effective separation of photogenerated electron-hole pairs.