Rutile titanium dioxide prepared by hydrogen reduction of Degussa P25 for highly efficient photocatalytic hydrogen evolution

Abstract

Degussa (Evonik) TiO₂ P25 consisting of a mixture of anatase and rutile crystallites is a well-known commercial material with high photocatalytic efficiency. The mixture of anatase and rutile phases in P25 is reportedly more active than the individual polymorphs of TiO₂. Contrary to this viewpoint, we demonstrate that H₂-reduced rutile TiO₂ is much more active than mixed-phase P25 for photocatalytic H₂ evolution under ultraviolet irradiation. An important factor to improve the photocatalytic activity of rutile TiO₂ is H₂ reduction treatment. H₂-reduced rutile TiO₂ outperforms anatase-rich TiO₂ because of the wider absorption range caused by its smaller band gap (3.0 eV for rutile and 3.2 eV for anatase). The apparent quantum efficiency for H₂ evolution of H₂-reduced rutile TiO₂ was estimated to be 46% under 390 nm irradiation, which was 3.3 times higher than that of mixed-phase P25. This highly efficient rutile photocatalyst is easily fabricated from P25 by H₂ reduction treatment at 700 °C for 2 h.