Soluble Gd6Cu24 clusters: effective molecular electrocatalysts for water oxidation

Abstract

The water oxidation half reaction in water splitting for hydrogen production is extremely rate-limiting. This study reports the synthesis of two heterometallic clusters (Gd₆Cu₂₄-IM and Gd₆Cu₂₄-AC) for application as efficient water oxidation catalysts. Interestingly, the maximum turnover frequency of Gd₆Cu₂₄-IM in an NaAc solution of a weak acid (pH 6) was 319 s⁻¹. The trimetallic catalytic site, H₂O–Gd^IIICu^II₂–H₂O, underwent two consecutive two-electron two-proton coupled transfer processes to form high-valent Gd^III–O–O–Cu^III₂ intermediates. Furthermore, the O–O bond was formed via intramolecular interactions between the Cu^III and Gd^III centers. The results of this study revealed that synergistic catalytic water oxidation between polymetallic sites can be an effective strategy for regulating O–O bond formation.