Controllable Synthesis of Mesoporous TiO₂ Polymorphs with Tunable Crystal Structure for Enhanced Photocatalytic H₂ Production

Abstract

Abstract Multiphasic titanium dioxide (TiO 2 ) possessing abundant heterophase junctions have been widely used for various photocatalytic applications. Current synthesis of multiphasic TiO 2 mainly involves the process of thermal treatment and multiple steps of rigorous reactions, which is adverse to controlling the crystal phases and phase ratios of multiphasic TiO 2 . Meanwhile, the resulting products have relatively low surface area and nonporous structure. Here, a facile polymer‐assisted coordination‐mediated self‐assembly method to synthesize mesoporous TiO 2 polymorphs with controllable heterophase junctions and large surface area by using polyethylenimine as the porogen in an acidic aqueous synthesis system is reported. Using this approach, the crystal phases (triphase, biphase, and monophase) and phase compositions (0–100%) are easily tailored by selecting the suitable acidic media. Furthermore, the specific surface areas (77–228 m 2 g −1 ) and pore sizes (2.9–10.1 nm) are readily tailored by changing the reaction temperature. The photocatalytic activity of mesoporous TiO 2 polymorphs is evaluated by photocatalytic hydrogen evolution. The triphasic TiO 2 exhibits an excellent photocatalytic H 2 generation rate of 3.57 mmol h −1 g −1 as compared to other polymorphs, which is attributed to the synergistic effects of heterophase junctions and mesostructure. The band diagram of possible electron transfer pathway for triphasic TiO 2 is also elucidated.