Insulating titanium oxynitride for visible light photocatalysis

Yuta Aoki; Sinisa Coh; Steven G. Louie; Marvin L. Cohen; Susumu Saito

doi:10.1103/PhysRevB.99.075203

paper

Insulating titanium oxynitride for visible light photocatalysis

arXiv:1701.06251 · doi:10.1103/PhysRevB.99.075203

Abstract

We propose a systematic approach to obtain various forms of insulating titanium oxynitrides Ti $_{n}$ N $_{2}$ O $_{2 n - 3}$ and we conduct a detailed study on its $n = 2$ case, Ti $_{2}$ N $_{2}$ O. We study the energetics and the electronic structures of Ti $_{2}$ N $_{2}$ O and compare these results with those of pristine and nitrogen-doped TiO $_{2}$ within the framework of the density-functional theory (DFT) and the GW approximation. We find that Ti $_{2}$ N $_{2}$ O is semiconducting with the calculated band-gap of 1.81 eV, which is significantly smaller than those of pristine TiO $_{2}$ rutile (3.14 eV) or anatase (3.55 eV). Furthermore, the reduction of the band-gap of Ti $_{2}$ N $_{2}$ O is realized not by lowering of the conduction-band minimum but by rising the valence-band maximum. Therefore the proposed Ti $_{2}$ N $_{2}$ O has suitable band-edge alignment for water-splitting photocatalysis. Finally, total energy calculations indicate that Ti $_{2}$ N $_{2}$ O is potentially easier to synthesize than nitrogen-doped TiO $_{2}$ . Based on these results, we propose Ti $_{2}$ N $_{2}$ O as a promising visible-light photocatalytic material.

10 pages, 7 figures