Electrochemical Analysis of MnO2 (α, β, and γ)-Based Electrode for High-Performance Supercapacitor Application

MnO2 is the most favorable material in power storage due to its technological significance and potential applications in pseudocapacitance (due to various oxidative states allowing efficient charge transfer to meet energy demands), where its properties are considerably influenced by its structure and surface morphology. In the present study, a facile hydrothermal route was used to produce different phases of MnO2 (α, β, and γ) with different morphologies. The electrochemical performance of the synthesized phases was studied in aqueous sodium sulfate as an electrolyte. X-ray diffraction, UV–Vis spectroscopy, and Fourier-transform infrared spectroscopy were used to characterize the synthesized material. The surface morphology and topography were examined using field-emission scanning electron microscopy. The direct band gap of α-, β-, and γ-MnO2 was found to be 1.86 eV, 1.08 eV, and 1.68 eV, lying in the semiconducting range, further enhancing the electrochemical performance. It was found that α-MnO2 had a maximum specific capacitance of 138 F/g at 1 A/g, and the symmetric device fabricated using α-MnO2 had a specific capacitance of 86 F/g at 1 A/g.