The reduction of H 2 O 2 on Pt electrodes in H 2 SO 4 solutions shows a various types of electrochemical oscillations, named sequentially from A to G, as has been reported previously. This paper shows that salts such as Na 2 SO 4 and K 2 SO 4 , which are often used as supporting electrolytes for electrochemical reactions, cause significant effects on the H 2 O 2 reduction. A new potential oscillation, named oscillations H, appears in the H 2 O 2 -H 2 SO 4 -Pt system when Na 2 SO 4 or K 2 SO 4 is added to the solutions. Oscillation H is induced by the cations originating from the salts, Na + and K + , though they do not react on Pt electrode. In the presence of Na + or K + , the local pH at the electrode surface becomes basic, and consequently the oxidation of HO 2 − , formed via a dissociation of H 2 O 2 (H 2 O 2 → HO 2 − + H + ), occurs on the electrode surface. Oxygen bubbles due to the HO 2 − oxidation evolve from the electrode synchronously with the potential oscillation. Detailed studies, including electrochemical impedance measurements and numerical simulation, reveal that oscillation H can be explained by an interplay of the HO 2 − oxidation and an autocatalytic effect involved in the H 2 O 2 reduction.
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Mukouyama et al. (2016) studied this question.
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