Facile synthesis of Ti³⁺-TiO₂ mesocrystals for efficient visible-light photocatalysis

Defect-rich TiO₂ mesocrystals were successfully synthesized by facile vapor hydrolysis method for the first time. The as-prepared TiO₂ mesocrystals showed typical mesoporous structure, and the specific surface area reached 124.88 m² g⁻¹. The as-prepared samples exhibited amazing visible light absorption and highly enhanced visible light photocatalytic activity for hydrogen production in comparison to that of P25 TiO₂, and the highest visible light photocatalytic activity of Ti³⁺ doped TiO₂ mesocrystals for hydrogen production reached 301.1 μmol g^-1 h^-1, which was about 131 times as high as that of P25 TiO₂ photocatalyst. It was the formation of Ti³⁺ species, the long carriers’ lifetimes and effective conduction pathways that highly enhanced the visible light photocatalytic activity of Ti³⁺-TiO₂ mesocrystals. Finally, the schematic illustration of possible photo-generated electrons and holes transfer mechanism and visible light photocatalytic mechanism of Ti³⁺-TiO₂ mesocrystals for hydrogen production were also proposed in detail.