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

Abstract

The influence of synthesizing temperature of manganese dioxide (MnO(2)) powders on their electrochemical reactivity in 1 M KOH was investigated. These powders were prepared chemically by the hydrothermal method by oxidation of Mn(2+) by ammonium peroxodisulphate. The observations by scanning electronic microscopy, energy-dispersive X-ray analyses, and transmission electron microscopy techniques on MnO(2) 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 MnO(2) synthesized at 90 degrees 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 MnO(2) powder synthesized at 90 degrees C shows the highest electrochemical reactivity in agreement with BET data. The X-ray powder diffraction identified the gamma-MnO(2), known as the most reactive species.

High-performance of bare and Ti-doped α-MnO2 nanoparticles in catalyzing the Oxygen Reduction Reaction

“…4 and Table 1 (7th column, 2nd and 4th lines) also show that MH_K samples have higher pore volume and higher average pore diameter than MH_N series. As previously stated, K þ and NH 4 þ cations have slightly different hydrated radii [27]: as reported by Benhaddad et al [10], this difference may influence the surface characteristics, such as surface area and pore volume. Indeed, since all the physicochemical parameters utilized in the synthetic route (such as temperature, pH, synthesis duration, hydrodynamic conditions, etc.)…”

“…Among these synthetic protocols, the wet route is commonly used for the preparation of manganese dioxide [13]. In particular, the effects of pH, concentrations [14], temperature [11,15], reactants [10], counter cations and anions [12] have been widely studied in order to obtain products with different behaviors, morphological structures (e.g. nanotubes, nanowires, nanorods, nanoflowers) and crystalline phases.…”

Ni(OH)2/RGO nanosheets constituted 3D structure for high-performance supercapacitors

“…To date, numerous transition-metal oxides/hydroxides electrode materials, such as NiO [10,11], Ni(OH) 2 [12][13][14][15], Co 3 O 4 [16], MnO 2 [17,18], have been carefully explored in the application-oriented study. In particular, Ni(OH) 2 is proved to be a promising electroactive material for the supercapacitors owing to its high theoretical specific capacitance, cost-effective, environmentally benign and high stability in alkaline electrolyte.…”

Chemical synthesis of hollow sea urchin like nanostructured polypyrrole particles through a core–shell redox mechanism using a MnO2 powder as oxidizing agent and sacrificial nanostructured template

“…MnO 2 : This method has already been reported in our previous publications [4,5]. It consists in mixing MnSO 4 , H 2 O (0.08 mol) with Na 2 S 2 O 8 (0.08 mol) and 150 mL of deionised water at room temperature.…”

“…Recently, the synthesis of nanomaterials has attracted a great scientific interest due to their unique physical, chemical, electrical, and magnetic properties, resulting mostly from their small size and their high specific area [1][2][3][4][5], which makes them eligible for a vast range of application domains.…”