Possibilities and Limits of Decreasing the Gap of Anatase TiO2 by Alloying with Nitrogen

• Published in: Journal of physical chemistry. C Vol. 125; no. 5; pp. 3192 - 3197
• Main Authors: Gupta, Verena Kristin, Lorke, Michael, Frauenheim, Thomas, Deák, Peter
• Format: Journal Article
• Language: English
• Published: American Chemical Society 11.02.2021
• Subjects: C: Physical Properties of Materials and Interfaces
• DOI: 10.1021/acs.jpcc.0c09986
• ISSN: 1932-7447

Nitrogen doping has been suggested to increase the photocatalytic activity of titanium dioxide in the visible. For this purpose, narrowing of the mobility gap (the gap between conductive states) would be necessary, but the effect of nitrogen doping in this respect is controversial. Using hybrid functional calculations on special quasi-random structures (SQS) to model anatase-TiO2–x N x alloys, we find a limited narrowing of the mobility gap. With increasing N-concentration the narrowing increases but, before becoming substantial, the formation of donor oxygen vacancies, which compensate the nitrogen acceptors, leads to the destruction of the crystal structure. Our results allow the semiquantitative interpretation of spectroscopic observations.