Preparation and characterization of nanostructured manganese oxide for supercapacitors

Nanostructured manganese oxides were synthesized by a sol-gel method using manganese acetate (MnAc₂) and citric acid (C₆H₈O₇) as precursors, and characterized by Brunauer-Emmett-Teller (BET) analysis, Barrett-Joyner-Halenda (BJH), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. The nano-rod structure of MnO₂ developed gradually when the calcination temperature varied from 380 to 580°C. As the pH increased, the pore size increased, while the specific surface area decreased. The effects of the pH and calcination temperature on the electrochemical properties of the nano-MnO₂ electrode, including the supercapacitive behavior, were investigated by cyclic voltammetry (CV) tests. The tests were performed between 0 and 0.8 V versus Ag/AgCl in 1 M Na₂SO₄ electrolyte at various scan rates (10-200 mVs^-1). The specific capacitance of the SP-380 sample, prepared at pH 6, was equal to 269.3 Fg^-1. After 300 cycles, approximately a 3.4% increase of the specific capacitance was measured, confirming the excellent cyclability.