Electrochemical water oxidation by in situ-generated copper oxide film from [Cu(TEOA)(H2O)2][SO4] complex

Although many noble-metal oxide catalysts show high activities and low overpotentials for water oxidation, there remain challenges in the sustainable developments of more inexpensive, efficient, and robust catalysts. Here, we report a heterogeneous copper oxide film toward water oxidation formed upon the oxidative polarization of an acetate electrolyte containing Earth-abundant Cu(II) salts in combination with commercially available triethanolamine (TEOA) as the catalyst precursor. A 1:1 molar ratio of TEOA coordinates to Cu(II) is favored in aqueous solution and the single crystal of the complex was obtained. The film has a modest overpotential of 550 mV and the catalytic performance of the material is demonstrated by long-term electrolysis at 1.3 V vs normal hydrogen electrode, a stable current density persists for at least 3 h, and a Faradaic efficiency of almost 100% is obtained.