Conjugated polyene-modified Bi2MO6 (M[dbnd]Mo or W) for enhancing visible light photocatalytic activity

Abstract

Nanohybrids of Bi2MO6 (MMo or W) and a conjugated polyene (CP) were successfully prepared by calcining precursor Bi2MO6/polyvinyl alcohol composites. The morphology, structure, and photocatalytic performance of the nanohybrids were investigated. The CP adheres to the surface of the Bi2MO6 hollow microspheres via the metal (Bi and Mo or W)OC bonds. Coordination interactions between the hydroxyl groups in polyvinyl alcohol and the metal (Bi and Mo or W) atoms in Bi2MO6 promote the formation of metal OC bonds in the calcination process. For the degradation of the model pollutant, Rhodamine B (RhB), under visible light irradiation, the Bi2MoO6/CP and Bi2WO6/CP nanohybrids exhibit photocatalytic efficiencies that are, respectively, four times and twice those of the corresponding pure Bi2MO6. The photocatalytic activity enhancement stems from the electron transfer through the metal OC bonds between Bi2MO6 and CP. Interestingly, two different mechanisms by which CP enhances the photocatalytic activity of Bi2MO6 were confirmed. For the Bi2MoO6/CP nanohybrids, the CP acts as an electron reservoir, accepting and shuttling the electrons from Bi2MoO6. For the Bi2WO6/CP nanohybrids, however, the CP acts as a photosensitizer, injecting electrons into Bi2WO6. The nanohybrids both exhibit good recyclability. The photocatalytic performance of the Bi2MO6/CP nanohybrids is comparable with that reported for Bi2MO6 modified using expensive conjugated carbon materials (CCMs) such as graphenes, fullerenes (e.g., C60), and carbon nanotubes. Thus, CP is an ideal substitute for these expensive CCMs in the preparation of composite photocatalysts, because of its low cost and simple preparation process.