Soluble Gd 6 Cu 24 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 (Gd 6 Cu 24 -IM and Gd 6 Cu 24 -AC) for application as efficient water oxidation catalysts. Interestingly, the maximum turnover frequency of Gd 6 Cu 24 -IM in an NaAc solution of a weak acid (pH 6) was 319 s -1 . The trimetallic catalytic site, H 2 O-Gd III Cu II 2 -H 2 O, underwent two consecutive two-electron two-proton coupled transfer processes to form high-valent Gd III -O-O-Cu III 2 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.