Bulk and surface properties of the Ruddlesden-Popper oxynitride Sr$_2$TaO$_3$N

TL;DR

This study uses DFT calculations to analyze the structural and electronic properties of the layered Sr$_2$TaO$_3$N oxynitride, revealing surface features that enhance photocatalytic performance by suppressing exciton recombination.

Contribution

It provides detailed insights into the surface and bulk properties of Sr$_2$TaO$_3$N, highlighting configurations that improve photocatalytic efficiency compared to previous materials.

Findings

Bulk favors in-plane cis anion order with TaO6 octahedral rotations.

TaON-terminated surface suppresses exciton recombination.

Surface states are higher in energy, aiding photocatalytic activity.

Abstract

Oxynitrides with the perovskite structure are promising candidates for photocatalysis under visible light due to their appropriate optical and electronic properties. Recently, layered perovskites have attracted attention for their improved performance with respect to the bulk perovskites in photocatalytic water splitting. In this paper, we investigate the structural and electronic properties of the layered Ruddlesden-Popper oxynitride Sr$_2$TaO$_3$N and its (001) surfaces using density functional theory (DFT) calculations. We find that the energetically favoured configuration of the bulk has an in-plane \textit{cis} anion order and exhibits rotations of the TaO$_6$ octahedra. Furthermore, we show that the TaON-terminated (001) surface suppresses exciton recombination due to higher-energy surface states, giving a potential explanation for the good photocatalytic performance.