Studies on MnO2 Nanorods and Their Application for Supercapacitor

Background: Recently, manganese dioxide MnO2 has attracted renewed attention of investigators. This is primarily due to its low cost, making it a potential material for various applications. Objective: The goal of the present work was to synthesize MnO2 nanorods and study their optical and electrochemical properties. Method: The method involves refluxing of potassium permanganate (KMnO4) and manganese chloride (Mncl2) mixture in isopropyl alcohol (IPA)-water system. The surface morphology, vibrational response and structural parameters were characterized using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman Spectroscopy, Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA) and BET surface area measurements. The optical properties of the synthesized material were investigated using PL and UV-Vis. Spectroscopy. Electrochemical properties of resulting product (as an electrode) were studied in two-electrode cell assembly, employing galvanostatic charge/discharge (GCD), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) techniques. Results: FESEM and TEM images show that material is in the form of nanorods. XRD analysis showed the tetragonal structure of synthesized product. Thermal stability up to 400 °C has been observed for the sample. The BET analysis of the sample showed the existence of large and small pores. A direct band-gap of 4.1 eV was observed. Specific capacitance of value 108.2 F g^-1 was measured for 1 M Na2SO4 electrolyte solution, at current density of 1 mA cm^-2. Conclusion: MnO2 nanorods were successfully prepared using chemical refluxing technique. The electrochemical studies show that MnO2 can be profitably used for energy storage applications.