Mesocrystalline Ti³⁺[sbnd]TiO₂ hybridized g-C₃N₄ for efficient visible-light photocatalysis

TiO₂ mesocrystals are often considered to be a fascinating and efficient photocatalyst because of its long lifetime carriers and effective conduction pathways. However, TiO₂ mesocrystals showed no visible light response and visible light photocatalytic activity. To overcome these shortages, mesocrystalline Ti³⁺[sbnd]TiO₂ (meso-TiO₂) and its composites are highly desired to have strong capacity for harvesting visible light and photocatalytic hydrogen production. In this work, Ti³⁺ doped TiO₂ mesocrystals were successfully prepared through oriented attachment mechanisms, and direct Z-scheme Ti³⁺ self-doped TiO₂ mesocrystals/g-C₃N₄ composites were also prepared by facile solvethermal method. The as-prepared Ti³⁺[sbnd]TiO₂ mesocrystals showed visible light absorption and photocatalytic activity for hydrogen production. Interestingly, the as-prepared Ti³⁺ doped meso-TiO₂/g-C₃N₄ composites displayed highly improved visible light absorption and visible light photocatalytic activity for hydrogen production, and the highest photocatalytic activity for hydrogen production was about 3748.46 μmol g⁻¹ h⁻¹ with an apparent quantum efficiency of 1.42% at 400 nm (sacrificial agent, triethanolamine) and 983.56 μmol g⁻¹ h⁻¹ (sacrificial agent, methanol), much higher than that of g-C₃N₄ and Ti³⁺ doped TiO₂ mesocrystals, mainly due to the high charge separation efficiency, long lifetime carriers and effective transport pathways. Finally, possible direct Z-scheme photocatalytic mechanism of Ti³⁺ doped meso-TiO₂/g-C₃N₄ composites were proposed in detail.