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

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 H-2-reduced rutile TiO2 is much more active than mixed-phase P25 for photocatalytic H-2 evolution under ultraviolet irradiation. An important factor to improve the photocatalytic activity of rutile TiO2 is H-2 reduction treatment. H-2-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 H-2 evolution of H-2-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 H-2 reduction treatment at 700 degrees C for 2 h.