Electrochemical Oscillation during H2O2 Reduction in Basic Solutions

Abstract

A new type of electrochemical oscillation has been found to appear as a current oscillation in the H2O2-NaOH-Pt system. The oscillation, named oscillation I, appears within the potential region where an N-shaped negative differential resistance (N-NDR) is observed. The N-NDR is attributed to the formation of under-potential deposited hydrogen (upd-H) which suppresses the reduction of HO2 - produced from H2O2. Moreover, oscillation I also appears in the H2O2-H2SO4-Pt system when the salts such as Na2SO4 and K2SO4 are added to electrolytes, because the local pH at the electrode surface even in H2SO4 solutions becomes basic during the H2O2 reduction. Electrochemical impedance measurements indicate that oscillation I is classified into an NNDR oscillator, and also that the N-NDR plays a crucial role in the positive feedback loop in oscillation I. The surface concentration of HO2 - plays a role as the slow process in the negative feedback loop.