Band-gap engineering in AB(O$_x$S$_{1-x}$)$_{3}$ perovskite oxysulfides: A route to strongly polar materials for photocatalytic water splitting

TL;DR

This study uses density functional theory to explore how epitaxial strain can induce polar distortions in AB(O$_x$S$_{1-x}$)$_{3}$ perovskites, increasing their band gaps to optimize them for photocatalytic water splitting.

Contribution

It demonstrates that applying epitaxial strain to AB(O$_x$S$_{1-x}$)$_{3}$ perovskites can enhance their polar properties and band gaps, making them suitable for photocatalytic applications.

Findings

BaZr$_y$Ti$_{1-y}$O$_2$S compounds show large polar distortions.

Strain-induced band gap increases make these materials suitable for water splitting.

Epitaxial strain can balance polar distortion and band gap requirements.

Abstract

Polar heterogeneous photocatalysts were shown to lead to enhanced charge-carrier separation that results in superior activity for example for photocatalytic water splitting. Promising photocatalyst materials such as oxynitrides can be rendered polar by epitaxial strain, which however also increases their band gap, making them unsuitable for visible light absorption. This suggests a trade-off between small band gaps and polar distortions - both being crucial for the catalyst's efficiency. In this paper we investigate, using density functional theory calculations, the suitability of strained AB(O$_x$S$_{1-x}$)$_{3}$ perovskites for photocatalytic water splitting. These materials normally have band gaps too small for water splitting but inducing polar distortions via epitaxial strain can increase the band gap to the suitable range. We find perovskite BaZr$_y$Ti$_{1-y}$O$_2$S compounds to be highly promising for photocatalytic water splitting due to large polar distortions and suitable band gaps.