Behavior of manganese dioxide electrodes in a system containing a solid protonic electrolyte

Abstract

The behavior of manganese dioxide electrodes containing powders of graphite and titanium as electroconducting additives is studied in a system with a solid protonic hydrated electrolyte (SPHE). The MnO2 reduction is accompanied by ion exchange between formed Mn2+ ions and structural protons of SPHE. The open-circuit potentials drift in the anodic direction and stabilize when the MnO2 composition at a boundary with SPHE is close to stoichiometric. The drift is due to conjugated reactions of the MnO2 reduction and the graphite oxidation process that decays with time. With increasing cathodic current density, the solid-phase reduction of MnO2 via an electronic-protonic mechanism becomes predominant. At low polarizing-current densities, the open-circuit and steady-state potentials remain passably stable until the exchange capacity of SPHE by protons is exhausted or MnO2 near the interface with SPHE is spent. The feasibility of using MnO2-SPHE-based amperometric sensors for assaying components whose oxidation in a gas medium yields protons is considered