In situ synthesis and enhanced visible light photocatalytic activities of novel PANI–g-C3N4 composite photocatalysts

Novel polyaniline–graphitic carbon nitride (PANI–g-C3N4) composite photocatalysts with different PANI:g-C3N4 ratios were synthesized by “in situ” deposition oxidative polymerization of aniline monomer in the presence of g-C3N4 powder cooled in an ice bath. The resulting PANI–g-C3N4 composite photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible diffuse reflection spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy (PL). The photoelectrochemical measurements were performed using several on–off cycles of visible light irradiation. The photocatalytic activities of the novel photocatalysts were evaluated using methylene blue as a target pollutant. The PANI–g-C3N4 composites exhibit obviously enhanced photocatalytic performance under visible light irradiation, which is much higher than that of TiO2 (P25). The synergistic effect between PANI and g-C3N4 is found to lead to an improved photo-generated carrier separation. A possible photocatalytic mechanism of PANI on the enhancement of visible light performance is proposed to guide further improvement of their photocatalytic activity.