An improvement of photocatalytic activity of TiO2 Degussa P25 powder

•Surface of TiO2 Degussa P25 powder is modified by annealing in air and in vacuum.•Essential changes in surface composition were confirmed by XPS.•An adsorption measurement exhibits several structural features.•By annealing in vacuum the photocatalytic activity can be significantly increased.•Specific kinetic constant calculations permit to reveal efficiency of adsorption. The photocatalytic activities of Degussa P25 powders annealed at various temperatures in vacuum and air were studied together with investigations of their compositions by XPS, of their crystal structures by XRD and of their specific surface areas by BET. It is shown that the photocatalytic activity of P25 powders was remarkably enhanced after vacuum annealing; the kinetic coefficient can be raised by 75% during annealing at 400°C. It is obvious that this enhancement is not related to the adhesion ability of the P25 powders.