Synthesis and photocatalytic activity of poly-o-phenylenediamine (PoPD)/TiO2 composite under VIS-light irradiation

Poly-o-phenylenediamine (PoPD)/TiO2 composite photocatalyst with high activity and easy separation was facilely synthesized using ultraviolet light photoinitiating method. In this method, hydroxyl radicals produced by TiO2 under the ultraviolet light irradiation replaced conventional oxidant such as ammonium persulfate (APS) to induce polymerization of o-phenylenediamine (oPD) monomer on the surface of TiO2. The factors that influence the synthesis of PoPD/TiO2 composite photocatalyst and the optimum reaction conditions were studied thoroughly. The as prepared PoPD/TiO2 composite photocatalyst was characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), and UV–vis absorption spectra. The results showed that a dense conductive PoPD layer with moderate thickness was formed on the surface of TiO2, which can favor adsorption of organic pollutants and make full use of visible light. The novel PoPD/TiO2 composite catalyst was evaluated for their photocatalytic activity towards the degradation of methylene blue (MB) under visible light irradiation. The results were compared with synthesized pure TiO2 nanoparticles and the enhanced degradation was obtained with PoPD/TiO2 composite photocatalyst. More significantly, the PoPD/TiO2 composite photocatalyst exhibited easy separation and less deactivation after several runs. The advantages of the prepared PoPD/TiO2 composite photocatalysts revealed its great practical potential in photocatalytic reactions.