A Binuclear Cobalt Complex in the Electrochemical Water Oxidation Reaction

Abstract

The water splitting reaction represents an appealing approach to store solar energy. The 4e−/4H+ oxidation of water generating O2 is considered as the bottleneck in this reaction and usually requires a rather large over potential. We report on the synthesis and application of a binuclear cobalt(III) complex, 1, with two μ-OH ligands and tripodal triazole ligands, L, in the electrochemical water oxidation reaction (WOR; L=tris((1-phenyl-1H-1,2,3-triazol-4-yl)methyl)amine). The cobalt(III) centres in the complex exhibit an octahedral coordination geometry and the complex is stable in water. Electrochemical studies revealed that solutions of 1NO3 catalyse the WOR in phosphate or borate buffer. However, further analysis showed, that 1NO3 is a precursor and decomposes under the applied potential. A smooth deposit is formed on the electrode surface, which is a highly active water oxidation catalysis. The deposit consists of mainly cobalt oxide/hydroxide, which accounts for the catalytic activity, and small amounts of 1NO3.