THE ORIGIN OF OSCILLATIONS DURING HYDROGEN-PEROXIDE REDUCTION ON GAASSEMICONDUCTOR ELECTRODES

The origin of current and potential oscillations during hydrogen perox ide reduction on n-type GaAs semiconductor electrodes is investigated. Impedance measurements clearly demonstrate that the current oscillati ons are caused by a negative impedance in conjunction with the electro lyte or external resistance. By considering a simple kinetic model whi ch combines earlier mechanistic models proposed for the H2O2 and H+ re duction on GaAs, it is shown that oscillations can occur only if the n egative impedance is caused by an anomalous dependence of the band ben ding on the electrode potential, i.e., if an increase of the Fermi lev el of the n-type semiconductor results in an increase in the band bend ing. This effect is assumed to be caused by a hydride layer formed ele ctrochemically during the concomitant proton reduction. Impedance meas urements confirm the role of the band-bending anomaly.