Hole-Phonon Relaxation and Photocatalytic Properties of Titanium Dioxide and Zinc Oxide: First-Principles Approach

First-principles calculations for the temporal characteristicsof hole-phonon relaxation in the valence band of titanium dioxideand zinc oxide have been performed. A first-principles methodfor the calculations of the quasistationary distribution functionof holes has been developed. The results show that the quasistationary distribution of the holes in TiO2 extends to an energylevel approximately 1 eV below the top of the valence band. Thisconclusion in turn helps to elucidate the origin of the spectraldependence of the photocatalytic activity of TiO2. Analysis ofthe analogous data for ZnO shows that in this material spectraldependence of photocatalytic activity in the oxidative reactionsis unlikely.