An electrochemical model for reduction of MnO2 with Fe2+ ions

Abstract

The reduction kinetics of MnO2 by Fe2+ ions in acidic solution have been studied. The effects of stirring rate, particle size, temperature, Fe2+ and H+ concentrations have been investigated. Diffusional resistances are negligible above 900 r.p.m. and the rate is controlled by electrochemical reaction. A mixed-potential model developed to describe metallic corrosion has been used in combination with the shrinking core model to explain the reaction kinetics. The overall reaction has been written in terms of cathodic and anodic half-cell reactions. The Tafel equation has been used as a starting point to derive a rate equation. A value of 0.5 has been obtained for charge transfer coefficients, which implies the existence of symmetrical charge barriers. The kinetics of the cathodic reduction reaction are first order with respect to the proton concentration.