Constructing Anatase–Brookite TiO2 Phase Junction by Thermal Topotactic Transition to Promote Charge Separation for Superior Photocatalytic H2 Generation

Phase junctions of photocatalysts can promote the separation of photogenerated charge carriers for efficient utilization of the carriers. Construction of phase junctions and establishing their structure–performance relationship are still required. Herein, polycrystalline TiO2 decahedral plates with different phases were synthesized by thermal treatment-induced topotactic transition of titanium oxalate crystals. The phase of TiO2 evolved from pure anatase to anatase–brookite, anatase–brookite–rutile, and then to anatase–rutile, while the morphology of the decahedral plates was well maintained. The biphase anatase–brookite was found to be most efficient in photocatalytic hydrogen generation. Specifically, the hydrogen generation rate of the biphase anatase–brookite TiO2 was nearly 2.4 times greater than that of the biphase anatase–rutile TiO2. The spatially resolved surface photovoltage measurements indicate the more efficient separation of photogenerated charge carriers and thus greater photocatalytic activity of the former. This work provides a strategy for developing efficient phase-junction photocatalysts.