Boron-doped rutile TiO₂/ anatase TiO₂/ ZrTiO₄ ternary heterojunction photocatalyst with optimized phase interface and band structure

To improve the photocatalytic performance of TiO₂-based heterostructures, Z-scheme/Ⅱ-type rutile TiO₂ (R)/anatase TiO₂ (A)/ZrTiO₄ ternary heterojunction photocatalyst was designed and prepared via a facile one-step calcining strategy. Phase interface and band structure of the materials were controlled and optimized by regulating R–TiO₂/A–TiO₂ mass ratio in the TiO₂ (A, R)/ZrTiO₄ structures using boron doping. The highest photocatalytic performance and excellent catalytic stability of Rhodamine B removal was observed from the heterojunction with a low R–TiO₂/A–TiO₂ mass ratio of 0.066, even after five testing cycles, accompanying with low photoluminescence intensity and electrochemical impedance, high photocurrent and charge carrier density (5.12 × 10²² cm⁻³), and a positive shift of valence band position (from +2.06 to + 2.16 eV). The increased photodegradation behaviour was due to the remarkably enhanced separation efficiency and improved redox ability of the photo-induced charge carriers as a result of the high content of oxygen vacancies and the formed anatase TiO₂/rutile TiO₂ Z-scheme heterojunction.