Electrocatalytic evaluation of a mononuclear copper(II) complex containing 2-pyridinecarboxylate ligand for water oxidation reaction

The growing demand for sustainable energy technologies has intensified interest in water electrolysis for green hydrogen production. In this context, a mononuclear copper(II) complex, [Cu(pic)₂] (pic = 2-pyridinecarboxylate), was investigated as a molecular electrocatalyst for the oxygen evolution reaction (OER). Structural characterization by FTIR, ESI-MS-Q-TOF, UV-Vis spectroscopy, and conductivity measurements confirmed the integrity and neutral character of the complex in aqueous solution. Electrochemical studies revealed enhanced catalytic activity above pH 9, associated with the formation of OH⁻-stabilized Cu(III) species and a proton coupled electron transfer mechanism. The Pourbaix diagram showed a slope of 20 mV/pH, indicating a 3H⁺/1e⁻ transfer ratio. The best performance was achieved at pH 12, with an overpotential of 748 mV at current density of 5 mA cm⁻². Stability tests demonstrated excellent durability, with negligible degradation (0.016%) after prolonged operation, highlighting the catalyst’s potential for OER applications.