Ti³⁺ Self-Doping of TiO₂ Boosts Its Photocatalytic Performance: A Synergistic Mechanism

Pollution remains one of the most significant global challenges. Photocatalysis consists of a new organic pollutant removal technology, with TiO₂ widely studied as a photocatalyst in the photocatalytic removal of water pollution. However, intrinsic TiO₂ has the disadvantages of weak visible light absorption, low electron separation, and transmission efficiency, as well as few active sites. In this study, anatase-phase Ti³⁺ self-doped TiO₂ (B-TiO₂) with a core-shell structure was successfully prepared by forming an amorphous layer rich in oxygen vacancies (OVs) and Ti³⁺ defects on the TiO₂ surface under a nitrogen atmosphere using NaBH₄ as a chemical-reducing agent. The visible light absorption performance of the catalyst was notably improved when exposed to light irradiation. The bending of surface energy bands facilitated the separation of photogenerated electron-hole pairs, and the core-shell structure allowed the electron-hole pairs to be transported to the surface of the catalyst and participate in the reaction faster. We observed that 92.86% of Rhodamine B (RhB) was degraded in only 5 min, an increase of 2.73 times that of the degradation rate observed in commercial P25. With extraordinary stability, the photocatalytic efficiency of the catalyst remained at 96.2% after five degradation cycles.