New Current and Potential Oscillations for Reduction Reactions on Platinum Electrodes in Acid Solutions Containing High Concentration Hydrogen Peroxide

Abstract

A new electrochemical oscillation (called oscillation B) appears, in addition to a reported one (called oscillation A), for reduction reactions on platinum electrodes in acid solutions containing hydrogen peroxide in case where the concentration is made high. Also, oscillation A becomes more pronounced and more stable as the concentration increases except the case of very high concentrations (≧ 1.1 M). Oscillation A appears in a narrow potential region just before hydrogen evolution, whereas oscillation B appears in a potential region of hydrogen evolution. Both oscillation A and B are strongly affected by the concentrations of as well as suggesting that they arise from the competition between the and reduction. It is concluded that the high and low current states for oscillation A correspond to the reduction and almost no reduction (nor hydrogen evolution), respectively, whereas the high and low current states for oscillation B correspond to the reduction and hydrogen evolution, respectively. Mechanisms for sudden transitions between these states are discussed qualitatively.