Photocatalytic Activity of TiO/g-CN Nanocomposites for Removal of Monochlorophenols from Water.

This research employed g-CN nanosheets in the hydrothermal synthesis of TiO/g-CN hybrid photocatalysts. The TiO/g-CN heterojunctions, well-dispersed TiO nanoparticles on the g-CN 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/g-CN, 1 g/L) and irradiation with UV-Vis light. Treatment of CP solutions with g-CN nanosheets or TiO 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/g-CN nanocomposite. Superoxide and hydroxyl radicals are key active species produced during CP photodegradation. In addition, the observed nitrogen and Ti defects and oxygen vacancies in the TiO/g-CN 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/g-CN nanocomposites may also enhance MCP degradation.