Two-Dimensional Perovskite Oxynitride K LaTa O N with an H /K Exchangeability in Aqueous Solution Forming a Stable Photocatalyst for Visible-Light H Evolution.

Undoped layered oxynitrides have not been considered as promising H -evolution photocatalysts because of the low chemical stability of oxynitrides in aqueous solution. Here, we demonstrate the synthesis of a new layered perovskite oxynitride, K LaTa O N, as an exceptional example of a water-tolerant photocatalyst for H evolution under visible light. The material underwent in-situ H /K exchange in aqueous solution while keeping its visible-light-absorption capability. Protonated K LaTa O N, modified with an Ir cocatalyst, exhibited excellent catalytic activity toward H evolution in the presence of I as an electron donor and under visible light; the activity was six times higher than Pt/ZrO /TaON, one of the best-performing oxynitride photocatalysts for H evolution. Overall water splitting was also achieved using the Ir-loaded, protonated K LaTa O N in combination with Cs-modified Pt/WO as an O evolution photocatalyst in the presence of an I /I shuttle redox couple.