Abstract
In this work, we used the mixed solution of manganese acetate and sodium sulfate to deposit manganese dioxide on the three-dimensional porous nickel foam that was previously soaked in alcohol, and then the effects of solution concentrations on their capacitance properties were investigated. The surface morphology, microstructure, elemental valence and other information of the material were observed by scanning electron microscope (SEM), Transmission Electron Microscope (TEM), X-ray photoelectron spectroscopy (XPS), etc. The electrochemical properties of the material were tested by Galvanostatic charge-discharge (GCD), Cyclic Voltammetry (CV), Chronoamperometry (CA), Electrochemical impedance spectroscopy (EIS), etc. The MnO2 electrode prepared at lower concentrations can respectively reach a specific capacitance of 529.5 F g−1 and 237.3 F g−1 at the current density of 1 A g−1 and 10 A g−1, and after 2000 cycles, the capacity retention rate was still 79.8% of the initial capacitance, and the energy density can even reach 59.4 Wh Kg−1, while at the same time, it also has a lower electrochemical impedance (Rs = 1.18 Ω, Rct = 0.84 Ω).
Highlights
The emergence of the fossil energy crisis has forced us to use new energy sources such as wind and solar energy
The morphologies and structures of the MnO2 films were characterized by emission scanning electron microscopy (ESEM) (Zeiss ULTRA 55 scanning electron microscope (SEM), 20 KV, Heidenheim, Germany) and transmission electron microscope (TEM, FEI Tecnai G2 F20 with an accelerating voltage of 200 kV, Hillsboro, OR, USA)
In 2019, Abolfath Eshghi et al proposed that there were the interactions between MnO2 and ethanol in the electrochemical process, and found that MnO2 could catalyze the ectrooxidation of ethanol, too [21]
Summary
The emergence of the fossil energy crisis has forced us to use new energy sources such as wind and solar energy. MnO2 is rich in content, is cheap, green and non-polluting, and has a high theoretical specific capacity (1370 F g−1 ) and a wide potential window, which is considered to be one of the most attractive electrode materials [4,5]. It is often difficult for MnO2 to maintain a large specific capacitance at a high charge and discharge rate due to its low conductivity [6,7]. The MnO2 electrode prepared in the precursor with a concentration of 0.06 M has lower charge transfer resistance (0.84 Ω), and due to the low resistance, this electrode has high rate performance (237.3F g−1 at a current density of 10 A g−1 ) and high energy density (59.4 Wh Kg−1 , 1 A g−1 )
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