Photocatalytic properties of BiOCl-TiO2 composites for phenol photodegradation

BiOCl-TiO2 composites were synthesized by sol-gel method; using two commercial BiOCl (P2600 and SB) with different BiOCl-TiO2 weight ratios. They were characterized by different techniques such as X-ray diffraction (XRD), electron microscopy (SEM, HRTEM and TEM), Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), time resolved micro-wave conductivity (TRMC) and UV-vis diffuse reflectance spectroscopy (UV-DRS). In addition, these composites (BiOCl-TiO2) were evaluated for the photodegradation of phenol (50 mgL(-1)) under visible irradiation (lambda > 450 nm). The results showed effective phenol degradation with the PTi-75 composite, which has 75% by weight of TiO2, obtaining up to 40% of degradation during 6 h of reaction. The SEM analysis showed that micro-sheets of BiOCl are irregularly embedded on agglomerates of TiO2 nanoparticles. A mechanism was proposed, which considers the excitation by the overlap of the BiOCl-TiO2 bands; where the TiO2 has a conduction band more electronegative than that of BiOCl, allowing that TiO2 electron of the conduction band can be transferred to conduction band of BiOCl; while the holes present in the valence band of BiOCl can be moved to TiO2 valence band preventing the electron-holes recombination.