Faradaic impedance studies of the autocatalytic reduction of H2O2 on Ag electrodes in HClO4

Abstract

Recently, it was shown that the reduction of hydrogen peroxide on silver in perchloric acid proceeds in two parallel paths. The normal reduction is observed at an overpotential of − 1.5 V whereas a second reduction reaction occurs at a significantly lower overpotential at − 1.0 V. The second reaction involves the unstable intermediate OH_ad, which also acts as a catalyst. Hence, the second reaction has been proposed to be an autocatalytic one. In this paper we present electrochemical impedance spectra together with numerical simulations for the faradaic impedance in the autocatalytic region based on previously suggested kinetic rate laws. It will be shown that the experimental data fit well with the results of the theoretical calculations, thus strongly supporting the autocatalytic mechanism.