Reactivity of Nanostructured MnO2 in Alkaline Medium Studied with a Micro-Cavity Electrode: Effect of Synthesizing Temperature

By Benhaddad, L.; Makhloufi, L.; Messaoudi, B.; Rahmouni, K. & Takenouti, H.
Published in ACS Applied Materials & Interfaces NULL 2009

Abstract

The influence of synthesizing temperature of manganese dioxide (MnO2) powders on their electrochemical reactivity in 1 M KOH was investigated. These powders were prepared chemically by the hydrothermal method by oxidation of Mn2+ by ammonium peroxodisulphate. The observations by scanning electronic microscopy, energy-dispersive X-ray analyses, and transmission electron microscopy techniques on MnO2 obtained at different temperatures show the formation of many nanometre scale sticks lumped together to form a spherical particle of several micrometers. The results obtained by BET and BJH methods reveal mesoporous texture, and the MnO2 synthesized at 90 °C presents the largest expanded surface area. The electrochemical reactivity of these powders in 1 M KOH was characterized with microcavity electrode by cyclic voltammetry and electrochemical impedance spectroscopy. The results illustrate that the nanostructured MnO2 powder synthesized at 90 °C shows the highest electrochemical reactivity in agreement with BET data. The X-ray powder diffraction identified the γ-MnO2, known as the most reactive species.

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