One-step hydrothermal synthesis of N/Ti3+ co-doping multiphasic TiO2/BiOBr heterojunctions towards enhanced sonocatalytic performance.

N/Ti3+ co-doping multiphasic TiO2/BiOBr heterojunctions (NT-TBx) were prepared by one-step in situ hydrothermal processes. The crystal phase, morphology, component, and optical properties of the heterojunctions were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope, X-ray photoelectron spectroscopy, and Ultraviolet-visible diffuse reflectance spectroscopy techniques, respectively. The as-prepared samples exhibit better sonocatalytic activity for the degradation methylene blue, Rhodamine B, and p-Nitrophenol aqueous solution compared with pristine TiO2 and N/Ti3+ co-doping multiphasic TiO2. Especially, the highest degradation ratio of methylene blue was achieved for NT-TB0.3 up to 98.2% after 50 min under ultrasonic irradiation. The high sonocatalytic activity has been kept after four cycles with the tiny decline, indicating the excellent stability of the as-prepared samples. The improvement of sonocatalytic activity could be attributed to the formation of doping level and multiphasic TiO2/BiOBr heterojunctions, which account for the absorption of long wavelength light and the electron-hole pair separation, respectively. Furthermore, superoxide radical (O2-) was demonstrated to be the main reactive species for the degradation of methylene blue under ultrasonic irradiation. This study provides a facile fabrication procedure for N/Ti3+ co-doping multiphasic TiO2/BiOBr heterojunctions and demonstrates an efficient route to promote the application of TiO2 in addressing environment-related issues.