Yttrium Tantalum Oxynitride Multiphases as Photoanodes for Water Oxidation

TL;DR

This study explores yttrium tantalum oxynitride multiphases as photoanodes for water oxidation, highlighting their visible light responsiveness and potential for solar water splitting, with performance improvements via cocatalyst loading.

Contribution

It reveals the existence of multiple yttrium tantalum oxynitride phases with different photoelectrochemical properties, and demonstrates the enhancement of water oxidation performance through cocatalyst application.

Findings

Yttrium tantalum oxynitride exists in multiple phases with bandgaps 2.13-2.31 eV.

N-doped YTaO4 shows promising water oxidation activity.

Loading IrOx cocatalyst improves photoelectrochemical performance.

Abstract

Perovskite yttrium tantalum oxynitride is theoretically proposed as a promising semiconductor for solar water splitting because of the predicted bandgap and energy positions of band edges. In experiment, however, we show here that depending on processing parameters, yttrium tantalum oxynitrides exist in multiphases, including the desired perovskite YTaON2, defect fluorite YTa(O,N,o)4, and N-doped YTaO4. These multiphases have bandgaps ranging between 2.13 and 2.31 eV, all responsive to visible light. The N-doped YTaO4, perovskite main phase, and fluorite main phase derived from crystalline fergusonite oxide precursors exhibit interesting photoelectrochemical performances for water oxidation, while the defect fluorite derived from low crystallized scheelite-type oxide precursors show negligible activity. Preliminarily measurements show that loading IrOx cocatalyst on N-doped YTaO4 significantly improves its photoelectrochemical performance encouraging further studies to optimize this new material for solar fuel production.