Oxygen and hydrogen peroxide reduction catalyses in neutral aqueous media using copper ion loaded glassy carbon electrode electrolyzed in ammonium carbamate solution

An aminated glassy carbon electrode (AGCE) can be obtained by the electrode oxidation of glassy carbon electrode in ammonium carbamate solution. In the cyclic voltammetric experiments, the electrode reduction of the dissolved oxygen began from −0.15 V vs. Ag/AgCl in neutral aqueous media when the aminated glassy carbon electrode was used as a working electrode although it began from −0.40 V vs. Ag/AgCl when a polished GCE was used. The nitrogen containing groups introduced by the electrode oxidation of carbamic acid must be related with the acceleration of the electron transfer rate of oxygen. Moreover, the new reduction wave of the dissolved oxygen appeared at +0.15 V vs. Ag/AgCl when copper (II) ion was coordinated to AGCE surface. This reduction potential of oxygen coincided with that of copper (II) ion and this fact suggests that the coordinated copper ion to the aminated carbon surface works as a redox mediator of oxygen. The reduction product of oxygen was monitored by rotating platinum ring – aminated glassy carbon disk electrode, and it was found that most of oxygen was reduced to water in a potential range negative than −0.4 V vs. Ag/AgCl. By using AGCE, it was recognized that the catalytic reduction of hydrogen peroxide was also taken place as well as oxygen reduction.