Interfacial reactivity and oscillating behavior of chalcopyrite cathodes during H2O2 reduction. I. Electrochemical phenomena

Nonlinear electrochemical phenomena are observed during reduction of H2O2 at CuFeS2 cathodes. The dynamic current-voltage curve from -1.0 to 0.0 VSCE appears N-shaped, with a pronounced current wave. If the potential is set constant in the region of the wave, sudden current spikes are observed. A remarkable feature is the onset of sustained current oscillations in the presence of a suitable resistance in series to the working electrode. Frequency and amplitude of oscillations are influenced by the resistance value and by mass transport. A potential modulation of small amplitude may trigger oscillations of the same frequency. Investigations performed with electrochemical techniques show that the phenomena are associated with corrosion of the electrode surface. It is proposed that the observed increases of the current originate from activation of a catalytic mechanism of H2O2 reduction involving copper species. A qualitative model is proposed on the basis of circuit analysis which accounts for the main aspects of the oscillating phenomena, including the role of the resistance and the effect of potential stimuli. The requirements for a more thorough kinetic treatment are discussed.