Yuta Aoki

Alternative structure of TiO2 with higher energy valence band edge

We propose an alternative structure of TiO2 anatase that has a higher energy oxygen p-like valence band maximum than the pristine TiO2 anatase and thus has a much better alignment with the water splitting levels. This alternative structure is unique when considering a large subspace of possible structural distortions of TiO2 anatase. We propose two routes towards this state and argue that one of them might have been realized in the recently discovered so-called black TiO2.

Impurities Effects on the Electronic Structure of Titanium Dioxide

Effects of substitutional doping of nitrogen to TiO2 are studied within the framework of the density-functional theory (DFT). We compare the total energy and the electronic structure of pristine TiO2 with those of nitrogen-doped TiO2. It is found that the smaller the concentration of doped nitrogen is, the more energy is required for the substitutional doping of the nitrogen atom in both rutile and anatase phases. This result suggests that the doped nitrogen atoms tend to be clustered. A sizable reduction of the photoexcitation energy is also suggested in the rutile structure.