Photocatalytic Activity of TiO 2 /g-C 3 N 4 Nanocomposites for Removal of Monochlorophenols from Water.

This research employed g-C 3 N 4 nanosheets in the hydrothermal synthesis of TiO 2 /g-C 3 N 4 hybrid photocatalysts. The TiO 2 /g-C 3 N 4 heterojunctions, well-dispersed TiO 2 nanoparticles on the g-C 3 N 4 nanosheets, are effective photocatalysts for the degradation of monochlorophenols (MCPs: 2-CP, 3-CP, and 4-CP) which are prominent water contaminants. The removal efficiency of 2-CP and 4-CP reached 87% and 64%, respectively, after treatment of 25 ppm CP solutions with the photocatalyst (40TiO 2 /g-C 3 N 4 , 1 g/L) and irradiation with UV-Vis light. Treatment of CP solutions with g-C 3 N 4 nanosheets or TiO 2 alone in conjunction with irradiation gave removal efficiencies lower than 50%, which suggests the two act synergically to enhance the photocatalytic activity of the 40TiO 2 /g-C 3 N 4 nanocomposite. Superoxide and hydroxyl radicals are key active species produced during CP photodegradation. In addition, the observed nitrogen and Ti 3+ defects and oxygen vacancies in the TiO 2 /g-C 3 N 4 nanocomposites may improve the light-harvesting ability of the composite and assist preventing rapid electron-hole recombination on the surface, enhancing the photocatalytic performance. In addition, interfacial interactions between the MCPs (low polarity) and thermally exfoliated carbon nitride in the TiO 2 /g-C 3 N 4 nanocomposites may also enhance MCP degradation.