Fabrication of polymer@TiO2 NPs hybrid membrane based on covalent bonding and coordination and its mechanism of enhancing photocatalytic performance

PVDF@TiO2 NPs hybrid membranes with different hybrid modes were fabricated. The chemical structure, surface characteristic features and optical properties of the hybrid membranes were characterised. The effects of different hybrid modes on photocatalytic performance are discussed for the first time. The results indicated that the membrane with both chemical bonding and coordination between TiO2 NPs and polymer matrix showed the best photocatalytic performance. Furthermore, the aggregation tendency of TiO2 NPs on the hybrid membrane surface was effectively suppressed and the band gap of TiO2 NPs was significantly reduced. The photogenerated electron-hole recombination rate was significantly decreased by the strongly electronegative fluorine (F), carboxyl and ester groups. Additionally, the negatively charged carboxyl groups on the surface of hybrid membrane facilitated the adsorption of methylene blue (MB) dye and promoted the adsorption-photocatalytic degradation of the MB. The photocatalytic degradation efficiency (η) of MB was higher than 95.4% and the η remained greater than 90% after 5 recycling cycles. Compared with membranes prepared by dip coating or blending, the grafted membrane exhibited higher degradation efficiency and improved recyclability. Therefore, this membrane provided a simple method for preparing stable hybrid membranes with better photocatalytic performance.