Synthesis and Electrochemical Performance of Manganese Dioxide Nanostructures from Nigerian Pyrolusite Ore for Supercapacitor Applications

This study synthesises and characterises manganese dioxide (MnO2) nanostructures derived from pyrolusite ore mined in Plateau State, North Central Nigeria, and evaluates their electrochemical performance as electrode materials for supercapacitor applications. Pyrolusite (beta-MnO2) is the most abundant manganese oxide mineral and provides a low-cost feedstock for supercapacitor electrode synthesis relevant to Nigeria's energy storage ambitions. Pyrolusite ore is digested in sulphuric acid and the resultant MnSO4 solution is used as the precursor for hydrothermal synthesis of alpha-MnO2 nanorods and delta-MnO2 nanosheets at varied synthesis temperatures (120 and 160 degrees Celsius) and durations. Products are characterised by XRD, SEM-TEM, BET surface area analysis, and FTIR. Electrochemical performance is evaluated in a three-electrode cell in 1 M Na2SO4 electrolyte using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. Specific capacitance, rate capability, and cycling stability over 2000 cycles are quantified. Findings indicate that alpha-MnO2 nanorods synthesised at 160 degrees Celsius achieve the highest specific capacitance of 312 F/g at 1 A/g with 87 percent capacitance retention after 2000 cycles. The high surface area (186 m2/g) and accessible pore structure of the nanorods are identified as key performance-enabling characteristics. Keywords: manganese dioxide, pyrolusite, supercapacitor, Plateau State, nanostructures.