Soluble GdCu 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 (GdCu-IM and GdCu-AC) for application as efficient water oxidation catalysts. Interestingly, the maximum turnover frequency of GdCu-IM in an NaAc solution of a weak acid (pH 6) was 319 s. The trimetallic catalytic site, HO-GdCu-HO, underwent two consecutive two-electron two-proton coupled transfer processes to form high-valent Gd-O-O-Cu intermediates. Furthermore, the O-O bond was formed intramolecular interactions between the Cu and Gd 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.