Issue 21, 2019

Vacancy diffusion barriers in TaON and Ta3N5 water-splitting photocatalysts

Abstract

Mixed anion semiconductors such as oxynitrides offer a wide range of properties that can be tuned for various catalytic applications, such as photocatalytic water splitting. In this work, first-principles simulations are used to predict the competing stabilities and mobilities of nitrogen and oxygen anion vacancies in the archetypal (oxy)nitride photocatalysts TaON and Ta3N5. The results demonstrate how the local Ta5+ coordination environment, vacancy defect charge and anion coordination number each influence the dominant ionic diffusion mechanism. Defect charge is intrinsically tied to the nature and kinetics of defect migration in these materials. Specifically, for neutral and low-charge defects in TaON, oxygen anion diffusion dominates ionic mobility, while higher charge states impede oxygen diffusion and simultaneously lower nitrogen diffusion barriers. This result provides a potential explanation for why TaON and Ta3N5 (and related (oxy)nitrides) are prone to becoming nitrogen deficient under catalytic operating conditions. Charge additionally stabilises oxygen anti-site defects in TaON, and oxygen impurity defects in Ta3N5, which is consistent with the tendancy of these materials to undergo oxidative decomposition, reforming pure oxide compounds such as Ta2O5. These insights highlight the importance of metal ion coordination and structural packing in retaining nitrogen content in oxynitride semiconductors for enhanced stability.

Graphical abstract: Vacancy diffusion barriers in TaON and Ta3N5 water-splitting photocatalysts

Supplementary files

Article information

Article type
Paper
Submitted
01 Mar 2019
Accepted
30 Mar 2019
First published
01 Apr 2019

J. Mater. Chem. A, 2019,7, 13029-13035

Vacancy diffusion barriers in TaON and Ta3N5 water-splitting photocatalysts

J. J. Bown and A. J. Page, J. Mater. Chem. A, 2019, 7, 13029 DOI: 10.1039/C9TA02280E

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements