Soluble Gd₆Cu₂₄ clusters: effective molecular electrocatalysts for water oxidation

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-(GdCu2II)-Cu-III-H2O, underwent two consecutive two-electron two-proton coupled transfer processes to form high-valent Gd-III-O-O-Cu-2(III) 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.