Observation of hydrogen oxidation wave using glassy carbon electrode fabricated by stepwise electrolyses in ammonium carbamate aqueous solution and hydrochloric acid

A glassy carbon electrode (GCE) electrooxidized in carbamic acid solution was electroreduced at −1.0 V vs. Ag/AgCl in 1 M HCl for a long time (20 h). Interestingly, we found that this multielectrolytic modified GCE exhibited the excellent electrocatalytic activity for the electrode oxidation of hydrogen molecule. This activity was significantly decreased by maleimide which selectively reacts with hydrazino-group rapidly. The potential range of hydrogen molecule oxidation lays from approximately −0.2 V to +0.3 V vs. Ag/AgCl in 1 M HCl electrolyte, and this fact indicates that the catalytic active site acquires its activity by the electrode oxidation of hydrazino-group to azo-group (diazene) and may lose that by further electrode oxidation to form diazo-group.