Titanium oxynitride microspheres with the rock-salt structure for use as visible-light photocatalysts

Novel photocatalysts (TiO2@TiO1-xNx) with the core-shell geometry were synthesized by controlled nitridation of TiO2 microspheres using ammonia gas. The oxynitride phases (TiO1-xNx) with a cubic rock-salt structure are exclusively formed on the surface of the TiO2 microspheres while the cores of the microspheres retain the TiO2 phase without nitrogen doping. Various spectroscopic data confirm the formation of the core-shell structure, denoted as TiO2@TiO1-xNx. The TiO2@ TiO1-xNx 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 TiO1-xNx 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.