Stable Cs2ReX6 (X – Cl, Br) vacancy-ordered perovskites for solar water splitting

Abstract

In this work, we report two vacancy ordered perovskites based on Cs₂ReX₆ (X – Cl, Br) for stable solar water oxidation. Instability of halide perovskites in aqueous media restricts their deployment in solar photoelectrochemical systems. The rhenium based VOPs reported in this work are shown to be highly stable in harsh pH media between pH1 and pH11 and show excellent visible and NIR absorption. The materials crystallize in the cubic phase similar to Cs₂PtX₆. The electrochemical stability window and flat band potential were determined for Cs₂ReX₆ and they were employed as photoanodes. Both these materials clearly show photocurrent under AM1.5G illumination and show excellent stability which is analysed by using chopped and continuous illumination.