Electrochemical oscillatory phenomena during reduction of hydrogen peroxide on mercury adatom-modified Au electrode

Acceleration of the reduction of hydrogen peroxide (H2O2) and electrochemic al oscillatory phenomena during the reduction of H2O2 on Hg adatom-modified Au polycrystalline electrodes in acidic, neutral and alkaline aqueous solu tions were first observed. The observed acceleration of the reduction of H2 O2 was explained by taking into account the electrode potential-dependent e lectrocatalytic behavior of the adsorbed species of OH- (OHad) on the Hg ad atom-modified Au electrode surface. The negative differential resistance (N DR) was observed in the potential region from 0.4 to 0.8 V vs. Ag/AgCl, whi ch is indeed characteristic of electrochemical oscillatory phenomena. Moreo ver, the oscillatory behavior was found to depend on the electrode rotation rate, the direction of potential scan, pH of the solution and the concentr ation of H2O2, similar to that previously observed on Au [100] and Ag polyc rystalline electrode surfaces during the reduction of H2O2. A probable expl anation for the observed current oscillation is given based on the comparis ion with the current oscillation behavior on Au [100] and Ag polycrystallin e electrodes. The reduction of H2O2 catalyzed by OHad (H2O2+H++OHad+e(-) -- > 2 OHad+H2O) is an autocatalytic. reaction which is characteristic of elec trochemical oscillatory phenomena and is controlled by the formation and di sappearance of OHad on the Hg adatom-modified Au electrode surface.