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

Abstract

Novel photocatalysts (TiO₂@TiO_1−xN_x) with the core–shell geometry were synthesized by controlled nitridation of TiO₂ microspheres using ammonia gas. The oxynitride phases (TiO_1−xN_x) 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@TiO_1−xN_x. The TiO₂@TiO_1−xN_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−xN_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.