Efficient electrochemical water oxidation mediated by a binuclear copper complex with a helical structure

Abstract

Herein, electrochemical water oxidation catalyzed by a binuclear copper complex [Cu₂(MePy₃P)₂] (1, MePy₃PH₂ = N,N′-bis[2-(2-pyridyl)methyl]pyridine-2,6-dicarbox-amide) with a helical structure is reported. Oxygen evolution occurs with a low onset overpotential of 483 mV, high turnover frequency of 18.04 s⁻¹ and moderate faradaic efficiency in neutral phosphate buffer solution, performing better than numerous copper-based homogeneous catalysts. Kinetic tests and electrochemical examinations reveal that complex 1 homogeneously catalyzes water oxidation. The mechanism of electrochemical water oxidation mediated by complex 1 is proposed according to electrochemical test results, which reveals that the two Cu cores of complex 1 undergo nucleophilic attack by water and then take part in the formation of an O–O bond. The outstanding catalytic activity of complex 1 may be attributed to the intramolecular interactions of its two adjacent Cu cores during the catalytic cycle. This work suggests that development of copper complexes with a neighboring multinuclear structure is a feasible strategy to obtain an efficient water oxidation catalyst.