Titanium oxynitride microspheres with the rock-salt structure for use as visible-light photocatalystsElectronic supplementary information (ESI) available. See DOI: 10.1039/c5ta06758h

Novel photocatalysts (TiO 2 @TiO 1− x N x ) with the core-shell geometry were synthesized by controlled nitridation of TiO 2 microspheres using ammonia gas. The oxynitride phases (TiO 1− x N x ) with a cubic rock-salt structure are exclusively formed on the surface of the TiO 2 microspheres while the cores of the microspheres retain the TiO 2 phase without nitrogen doping. Various spectroscopic data confirm the formation of the core-shell structure, denoted as TiO 2 @TiO 1− x N x . The TiO 2 @TiO 1− x N x materials showed superior photocatalytic activities for the decomposition of methylene blue as well as the generation of photocurrent under visible-light. It is evident that the TiO 1− x N x phase is the key element to induce the photocatalytic activity. Specifically, the partial doping of nitrogen into the TiO matrix is crucial for visible-light absorption. Novel photocatalysts (TiO 2 @TiO 1− x N x ) with the core-shell structure, prepared by controlled nitridation of TiO 2 microspheres, show photocatalytic activity under visible-light irradiation.