Catalytic reactions of bis(1,10-phenanthroline) cuprous complex with hydrogen peroxide at glassy carbon and pyrolytic graphite electrodes

Abstract

The catalytic reduction of H 2O 2 by [Cu(phen) 2] 2+ (phen = 1,10-phenanthroline), which plays a role in the degradation of DNA, was investigated electrochemically at glassy carbon (GC) and pyrolytic graphite (PG) electrodes. At the GC electrode, [Cu(phen) 2] 2+ was reduced at ca. −0.1 V vs. SCE almost reversibly under diffusion control. The product was adsorbed weakly on the electrode. The current of H 2O 2 reduction catalyzed by [Cu(phen) 2] + was observed in the biological pH domain. The reaction rate constant at the GC electrode was evaluated from variations of the catalytic current with potential sweep rate and concentration of H 2O 2, and is given by (4.4±0.3) dm 3 mol −1 s −1. The PG electrode was employed for immmobilization of the complex. Two cathodic adsorption waves were observed at −0.1 and −0.3 V vs. SCE, one being due to reduction of [Cu(phen) 2] 2+ and the other probably of [Cu(phen)] 2+. Addition of H 2O 2 gave rise to a catalytic current at the potential corresponding to the second wave. Thus the catalytic reaction with the adsorbed species is different from that with the complex in solution. The heterogeneous rate constant was estimated and found to be larger than the rate constant of the homogeneous reaction.