Branched core-shell a-TiO 2 @N-TiO 2 nanospheres with gradient-doped N for highly efficient photocatalytic applications

A branched core-shell nanosphere composed of an anatase TiO 2 (a-TiO 2 ) core and a TiO 2 nanobranch shell with gradient-doped N (a-TiO 2 @N-TiO 2 ) is synthesized by a simple in situ doping method, in which mixed crystal anatase-rutile TiO 2 (ar-TiO 2 ) nanosphere is first prepared by oxidizing Ti using H 2 O 2 , and then is etched by NH 3 middotH 2 O to form (NH 4 ) 2 TiO 3 nanobranches, which is converted into a-TiO 2 @N-TiO 2 following an ambient annealing process. The diameter of a-TiO 2 core is similar to 500 nm, and the thickness of NTiO 2 branched shell is similar to 100 nm with gradually increased N concentration from the bottom to the edge. Ultra-thin amorphous coating layers on the branches are also observed. The morphology of the composites could be further tuned by the amount of NH 3 middotH 2 O, and its effect on the photocatalytic performance is also investigated. The optimized a-TiO 2 @N-TiO 2 shows an outstanding hydrogen evolution rate of 308.1 mu mol g -1 h -1 under air mass (AM) 1.5 illumination, and also exhibits highly active in photocatalytic degradation of various refractory organic pollutants, including organic dyes, phenols, antibiotics, and personal care products, with removal ratios higher than 96% after 2 h operation. This can be due to the gradient-doped N-TiO 2 nanobranches, which not only provide bending band structure and defect level derived from the N impurities and O vacancies, resulting the formation of n-n + heterojunctions to improve the charge separation, but also enhance the charge transfer at the liquid-solid interface due to the numerous nanobranches and amorphous coating layers.(c) 2023 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.

Automated summary

A branched core-shell nanosphere composed of an anatase TiO2 core and a TiO2 nanobranch shell with gradient-doped N has been synthesized. The optimized nanosphere exhibits outstanding hydrogen evolution rate and high activity in photocatalytic degradation of various refractory organic pollutants.