Peculiarities of the Behavior of Porous Titanium Dioxide in the Photocatalytic Evolution of Molecular Hydrogen from Aqueous Ethanolic Solutions

Peculiarities of the behavior of porous titanium dioxide in the photocatalytic evolution of molecular hydrogen from aqueous ethanolic solutions are shown to arise from the accumulation of long lived "free" electrons and titanium(III) ions in the irradiated samples, and the slow transport of electrons to the surface of the TiO₂ particles. This explains the dependence of the effectiveness of the process on both the intensity of the irradiation and on the length of time the irradiated samples are kept in the dark.