Phosphorus-doped g-C3N4 nanosheets coated with square flake-like TiO2: Synthesis, characterization and photocatalytic performance in visible light

Photocatalysts Phosphorus-Doped g-C 3 N 4 (P(x%)-g-C 3 N 4 ) were successfully prepared by a two-step method using melamine and phosphonitrilic chloride trimer (Cl 6 N 3 P 3 ). Then, the Phosphorus-doped g-C 3 N 4 sheets coated with TiO 2 nanoparticles (P(x%)-g-C 3 N 4 /TiO 2 ) were prepared by solvent-thermal method. The as-prepared P(x%)-g-C 3 N 4 /TiO 2 composites showed enhanced light absorption and photocatalytic properties in visible light region. The morphology of g-C 3 N 4 nanosheets and square flake TiO 2 nanoparticles were analyzed with field emission scanning electron microscopy (FESEM) and scanning electron microscopy (SEM). X-ray photoelectron spectroscopy (XPS) proved that the P-C bonds were generated in P(x%)-g-C 3 N 4 . Photoluminescence (PL) spectra revealed that the phosphorus doping improved the separation and transfer of photogenerated electrons and holes in P(x%)-g-C 3 N 4 , UV–vis diffuse reflectance spectra (UV-vis DRS) indicated that the P(x%)-g-C 3 N 4 /TiO 2 heterostructure enhanced the absorption of visible light. The photocatalytic activity of the P(x%)-g-C 3 N 4 was evaluated by photocatalytic degradation of Methyl Blue (MB) under visible light irradiation. The result indicated that the P(0.1%)-g-C 3 N 4 /TiO 2 composite present considerably high photocatalytic degradation activities on MB, and the degradation of MB by P(0.1%)-g-C 3 N 4 /TiO 2 were 5.1 times and 2.9 times as high as that of g-C 3 N 4 and P25, respectively. At the end of article, a possible photocatalytic mechanism was discussed based on the experimental results.