First mononuclear copper(II) electro-catalyst for catalyzing hydrogen evolution from acetic acid and water

The reaction of 2,3-bis(2-hydroxybenzylideneimino)-2,3-butenedinitrile (H2L) and CuCl2·2H2O affords a copper(II) complex [CuL] 1, a new molecular electrocatalyst, which has been determined by X-ray crystallography. Electrochemical studies indicate that the catalyst is the first mononuclear copper(II) species with a turnover frequency of 457 (pH 7.0) moles of hydrogen per mole of catalyst per hour at an overpotential of 817 mV vs SHE, which is higher than some reported molecular catalysts for electrochemical hydrogen production from neutral water. Sustained proton reduction catalysis occurs at glassy carbon (GC) to give H2 over a 72 h electrolysis period with 91.5% Faradaic yield and no observable decomposition of the catalyst.