Non-covalent ligand-oxide interaction promotes oxygen evolution

Strategies to generate high-valence metal species capable of oxidizing water often employ composition and coordination tuning of oxide-based catalysts, where strong covalent interactions with metal sites are crucial. However, it remains unexplored whether a relatively weak “non-bonding” interaction between ligands and oxides can mediate the electronic states of metal sites in oxides. Here we present an unusual non-covalent phenanthroline-CoO(2) interaction that substantially elevates the population of Co(4+) sites for improved water oxidation. We find that phenanthroline only coordinates with Co(2+) forming soluble Co(phenanthroline)(2)(OH)(2) complex in alkaline electrolytes, which can be deposited as amorphous CoO(x)H(y) film containing non-bonding phenanthroline upon oxidation of Co(2+) to Co(3+/4+). This in situ deposited catalyst demonstrates a low overpotential of 216 mV at 10 mA cm(−2) and sustainable activity over 1600 h with Faradaic efficiency above 97%. Density functional theory calculations reveal that the presence of phenanthroline can stabilize CoO(2) through the non-covalent interaction and generate polaron-like electronic states at the Co-Co center.