Fabrication of Ti3+ self-doped TiO2(A) nanoparticle/TiO2(R) nanorod heterojunctions with enhanced visible-light-driven photocatalytic properties

Abstract

Ti³⁺ self-doped TiO₂(A)/TiO₂(R) heterojunctions comprising anatase TiO₂ (TiO₂(A)) nanoparticles and rutile TiO₂ (TiO₂(R)) nanorods were synthesized by a simple hydrothermal method using Zn as the reductant. The structure, crystallinity, morphology, and chemical state of the as-prepared samples were characterized by X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and UV-Vis diffuse reflectance spectroscopy. The heterojunction architectures and Ti³⁺ contents could be controlled by adjusting the temperature of the hydrothermal treatment. Zn acts as a reducing agent and Zn²⁺ stabilizes the oxygen vacancies. Meanwhile, the generated ZnO clusters promote phase transformation from TiO₂(A) to TiO₂(R). The visible-light photocatalytic degradation of dyes was analyzed. The Ti³⁺ self-doped TiO₂(A)/TiO₂(R) heterojunctions exhibited an extended visible light absorption and higher visible-light photocatalytic activity than that of commercial P25 TiO₂ in the photodegradation of Methylene blue and Rhodamine B under visible-light irradiation (λ ≥ 400 nm). Ti³⁺ self-doping expanded the light-response range, and the formed heterojunctions at the interface of TiO₂(A) nanoparticles and TiO₂(R) nanorods efficiently reduced the recombination of photoinduced electron–hole pairs. This self-doping increased the lifetime of charge carriers by 15 times that of P25 TiO₂ and enhanced the corresponding photocatalytic activity of the self-doped heterojunctions.