Effect of charge balance vacancies on the ultraviolet photocatalytic activity of Fe3+-doped anatase

The presence of Fe3+ dopant ions rastically decreases the activity of TiO2 powders in the photocatalytic decolorization of methyl orange. A comparison of the photocatalytic activities of the 0.6 at% Fe3+: TiO2 and 0.6 at% Cr3+: TiO2 samples before and after their hydrogen annealing shows that this negative effect is mainly due to the formation of charge balance oxygen vacancies VO, and it does almost not depend on the physicochemical properties of M3+ dopants. The 57Fe Mossbauer spectrum of 2 at% Fe3+: TiO2 indicates that nearly every other Fe3+ ion introduced into TiO2 possesses a vacancy VO in its nearest surrounding.