Influence of Moringa oleifera gum on two polymorphs synthesis of MnO 2 and evaluation of the pseudo-capacitance activity
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Influence of Moringa oleifera gum on two polymorphs synthesis of MnO2 and evaluation of the pseudocapacitance activity Veeman Sannasi1 and Karuppuchamy Subbian1,* 1
Department of Energy Science, Alagappa University, Karaikudi, Tamil Nadu 630003, India
Received: 9 June 2020
ABSTRACT
Accepted: 17 August 2020
This work reports the preparation of two polymorphs of MnO2 such as a-MnO2 and b-MnO2 by simple microwave method using natural Moringa oleifera gum. The concentration of M. oleifera gum solution influences the formation of aMnO2 and b-MnO2, and the structural formation of the metal oxides was confirmed by powder X-ray diffraction analysis. According to the surface analysis of the prepared materials studied through scanning electron microscopy and transmission electron microscopy, nanocacti a-MnO2 and rice husk shaped bMnO2 nanorod morphology were observed. The fabricated a-MnO2 and b-MnO2 electrode materials on Ni foam showed good electrochemical behaviours in the cyclic voltammogram using a three-electrode system and exhibited a specific capacitance of 150 Fg-1 and 92.8 Fg-1 at a current density of 0.5 Ag-1 in the galvanic charge–discharge studies, respectively. Furthermore, cycling stability study of the a-MnO2 material showed capacitance retention of 95.4% at a current density of 6 Ag-1 after 2000 galvanostatic charge–discharge cycles.
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Springer Science+Business
Media, LLC, part of Springer Nature 2020
1 Introduction In the last two decades, enormous attention has been paid on the preparation of new materials for energy conversion and energy storage applications aroused by increasing the global energy crisis, depletion of fossil fuel, environmental aspects and excessive usage of miniaturisation electronic devices. Various transition metal oxides/hydroxides, chalcogenides, have been used for energy conversion and energy storage applications [1–4] and particularly, metal
oxides attract all in the energy field due to its ease of preparation, stability and high efficiency. For example, SiO2, RuO2, TiO2 and SnO2 have been extensively used as a material for photovoltaic, supercapacitor, electrocatalyst and photocatalyst, respectively. Albeit the high performance of these metal oxides in their respective applications, they have suffered by their low abundance in the earth’s crust and high cost of processing in the case of RuO2 [5]. The high cost and low abundance of the best performing materials pave great attention to focus on low cost, high abundance metal oxides such as NiO, ZnO, CuO, Co3O4, Fe2O3,
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https://doi.org/10.1007/s10854-020-04272-z
J Mater Sci: Mater Electron
V2O5 and MnO2 [6–9]. Among them, MnO2 has been more attracted material for supercapacitor application due to their high theoretical capacitance, wide working potential range, low cost and environmental friendly. Variety of preparation methods such as hydrothermal, sol–gel, soft template, co-precipitation, micro-emulsion, spray, electrochemical reduct
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