Pentadentate Copper(II)-amidate complex as a precatalyst for electrocatalytic proton reduction

Electrochemical reduction studies of a mononuclear Cu(II) complex bearing a pentadentate amidate ligand under both aqueous and non-aqueous media revealed the deposition of a heterogeneous film on the electrode. The heterogeneous film was grown on an FTO working electrode by control potential electrolysis (CPE) at −0.9 V vs. NHE for 3 h (pH 3.0, phosphate buffer). Characterization of the electrodeposited film by SEM, EDX and XPS indicates the preferential formation of Cu2O. The FTO/Cu2O cathode, thus formed, exhibits electrocatalytic proton reduction in acidic aqueous medium (pH 3.0) with 95% Faradaic efficiency at moderate overpotential (η = 320 mV at onset). The overpotential required to reach 1 mA/cm2 is 530 mV. The FTO/Cu2O cathode maintained a current density of 2.5 mA cm−2 for a period of 3 h and showed stability after 200 scan cycles.