Preparation of annular TiO2 nanoparticles constructed by high-energy surfaces and enhanced visible-light photocatalytic activity

Abstract

Controlling overexposed facets with high energy is pivotal for various applications, particularly catalytic reactions which occur on the surfaces of nanostructures. Herein, we report a combined solvothermal and etching method to synthesize anatase TiO₂ nanocrystals with energetic exposed facets, which exhibit enhanced visible light photodegradation activity towards RhB. Electron microscopic photographs revealed that the initially prepared nanocrystals had a hierarchical structure stacked by secondary nanoplates, and time dependent experiments proved that the formation process followed an oriented aggregation mechanism and a subsequent grain growth. In addition, quantum mechanical calculations revealed that the etching process could occur along three directions of TiO₂ nanocrystals, and the formation of Ti³⁺ defects was thermodynamically favorable, which was further demonstrated by XPS spectra. The reasons for the enhanced photodegradation activity are also discussed through the production of reactive oxygen species (ROS), which revealed that the adsorption of surface hydroxyls and H₂O may be the main reason for this enhancement.