Reactivity of Nanostructured MnO_2 in Alkaline Medium Studied with a Microcavity Electrode: Effect o

• 作 者: L.Benhaddad L.Makhloufi B.Messaoudi1 K.Rahmouni H.Takenouti
• 机 构: Laboratoire de Technologie des Matériaux et Génie des Procédés (LTMGP),Département de Génie des Proc
• 出 处: Journal of Materials Science & Technology
• 发表日期: 2011年07期
• 关键词: oxidizing powders cathodic reactivity Medium hydrothermal impedance voltammetry

The synthesis of MnO2 powders by hydrothermal method with different oxidizing agents has been successfully achieved. The characterizations by scanning electron microscopy, energy-dispersive X-ray analyses, transmission electron microscopy, and X-ray diffraction techniques confirm the synthesis of nanostructured γ-MnO2 powders. The electrochemical reactivity of these powders in 1 mol/l KOH is investigated by cyclic voltammetry and electrochemical impedance spectroscopy (EIS) by using microcavity electrode. The results reveal that the MnO2 synthesized with Na2S2O8 shows the highest electrochemical reactivity in the test medium. This is due both to its large expanded surface area and its crystallographic variety γ-MnO2 formed in the matrix of ramsdellite, which is largely used as cathodic material for primary batteries. However, the presence of pyrolusite in the structure of γ-MnO2 synthesized with (NH4)2S2O8 decreases its electrochemical reactivity due to its narrow 1×1 size tunnel, which hinders the protons insertion.

The synthesis of MnO2 powders by hydrothermal method with different oxidizing agents has been successfully achieved. The characterizations by scanning electron microscopy, energy-dispersive X-ray analyzes, transmission electron microscopy, and X-ray diffraction techniques confirm the synthesis of nanostructured γ-MnO2 The electrochemical reactivity of these powders in 1 mol / l KOH is investigated by cyclic voltammetry and electrochemical impedance spectroscopy (EIS) by using microcavity electrode. The results reveal that the MnO2 synthesized with Na2S2O8 shows the highest electrochemical reactivity in the test medium. This is due both to its large expanded surface area and its crystallographic variety γ-MnO2 formed in the matrix of ramsdellite, which is largely used as cathodic material for primary batteries. However, the presence of pyrolusite in the structure of γ-MnO2 synthesized with (NH4) 2S2O8 decreases its electrochemical reactivity due to its narrow 1 × 1 size tunnel, which hinders the protons insertion.