Ti³⁺ self-doped rutile/anatase/TiO₂(B) mixed-crystal tri-phase heterojunctions as effective visible-light-driven photocatalysts

Ti³⁺ self-doped rutile/anatase/TiO₂(B) mixed-crystal tri-phase heterojunctions photocatalysts are fabricated via hydrothermal approach and mechanochemical process, followed by in-situ solid-state chemical reduction approach. The as-prepared samples are characterized by X-ray diffraction, Raman, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and UV–vis diffuse reflectance spectroscopy. The photocatalysts are consisted by anatase/rutile TiO₂ nanoparticles and 1D TiO₂(B) single-crystalline nanorods, which form rutile/anatase/TiO₂(B) tri-phase heterojunctions. The visible-light-driven photocatalytic degradation rates of methyl orange and phenol are up to ∼98 and 97%, which are 2.2 and 1.8 times higher than that of commercial Degussa P25, 2.3 and 2.2 times higher than that of pure TiO₂(B) as well. The enhancement can be attributed to the synergistic effect of special nanostructure, tri-phase heterojunctions, oxygen vacancy and Ti³⁺ self-doping, which facilitates the absorption of visible light and the spatial separation of photo-generated charge carriers. This work provides a new perspective for designing high-active visible-light-driven photocatalyst in future.