Electrocatalytic Water Oxidation by a Trinuclear Copper(II) Complex

Abstract

Considering the ongoing decrease in the cost of electricity, the development of electrocatalytic processes will gain increasingly more importance in the future. Moreover, with the dwindling of the primary energy source that drives our society, fossil fuels, and the consequences that their utilization has on the environment, it is pivotal to find alternative sustainable energy sources from renewable and carbon free resources. Artificial photosynthesis is a promising strategy for meeting the growing energy demands, where a crucial half-reaction in both natural and artificial photosynthesis is water oxidn. (2H₂O --> O₂ + 4H+ + 4e-), using water as a source of electrons and protons. Inspired by nature, where water oxidn. occurs at the Mn4CaO5 active site of the oxygen evolving complex (OEC) of photosystem II, there has been growing interest in synthetic multinuclear catalysts for promoting intramol. O-O bond formation, with an advantageous redox flexibility for multi-electron transfer arising from the multinuclear core. Here, we employ a mol. trinuclear copper(II) complex, [(DAM)Cu₃(µ³-O)]Cl₄ (DAM = dodecaaza macrotetracycle), as catalyst precursor for electrocatalytic water oxidn. Based on electrochem. studies, we show that this complex is likely an active homogeneous electrocatalyst for water oxidn. in aq. phosphate buffer soln. enabling oxygen evolution with a turnover frequency of approx. 6.0 s⁻¹ at pH =7.