Enhancing visible-light photocatalytic activity of g-C3N4 by doping phosphorus and coupling with CeO2 for the degradation of methyl orange under visible light irradiation

CeO2/P-C3N4 composite photocatalysts were designed by doping phosphorus and coupling with CeO2 species. The structure and optical properties of the as-prepared samples were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy and photoluminescence spectroscopy. The photocatalytic activity of the CeO2/P-C3N4 was evaluated by photocatalytic degradation of methyl orange (MO) under visible light irradiation (lambda > 420 nm). The results indicated that the optimum photocatalytic activity of CeO2/P-C3N4 at a weight content of 13.8% CeO2 for the degradation of MO was 7.4 and 4.9 times as high as that of pure CeO2 and g-C3N4, respectively. The remarkable enhancement of photocatalytic activity could be attributed to the synergistic effect between CeO2 and P-C3N4, which was found to extend the visible light absorption range, enhance visible light absorption and improve photogenerated electron-hole pairs separation efficiency after doping phosphorus and coupling with CeO2. Additionally, the superoxide radical anions (O-center dot(2)-) and holes (h(+)) were considered as the main reactive species during the photodegradation MO process, and a possible photocatalytic mechanism over CeO2/P-C3N4 composite photocatalyst was proposed based on the experimental results.