Chemical Engineering

High effi ciency with stable performance and utilization of visible light is a key challenge to sunlight-induced photochemical generation of H₂, the cleanest energy carrier. Recently, black TiO_2-x materials were achieved by creating oxygen vacancies and/or defects at the surface using diff erent methods. Fascinatingly, they exhibited an extended absorption in VIS and IR as well as UV light, along with a band gap decrease from 3.2 (anatase) to ~1 eV. However, despite the dramatic enhancement of optical absorption of black TiO_2-x material, it fails to show expected visible light-assisted water splitting effi ciency.

 

                                                       

Therefore, a new reduced TiO₂ material with optimized properties would be highly desired for visible light photocatalysis. Herein, we report H-doped reduced TiO2-x nanoparticles prepared by a controlled reduction via the simultaneous presence of two active reducing species, [Mg] and [H] in a confined microenvironment at the surface of TiO₂. Th is new material exhibits outstanding activity (31.4 mmolg-1h-1) and excellent stability aft er Pt deposition for photochemical H₂ generation from methanol-water in simulated sunlight. Th e excellent photoactivity of H:TiO_2-x is attributed to the oxygen vacancies and H doping at the TiO₂ surface generated by [Mg] and [H]. The photocatalyst works at wavelengths <700 nm and exhibits reasonable visible-light activity with a quantum yield of 17.8, 7.62 and 3.72% at 400, 420 and 454 nm, respectively, along with an exceptionally high turnover number (238680) with respect to Pt. Th is outstanding activity can be correlated with the extended absorption of visible light, perfect band position, presence of an appropriate amount of Ti3+ and oxygen vacancy and slower charge recombination.