Synthesis and electrochemical characterization of amorphous MnO 2 for electrochemical capacitor

Abstract

Amorphous MnO 2 was synthesized by an improved reduction reaction. The synthesized product was characterized physically by thermogravimetric and differential thermal analysis (TG-DTA), X-ray diffraction (XRD) and transmission electron microscope (TEM). Electrochemical characterization was performed using cyclic voltammetry and chronopotentiometry in a 0.5 mol/L Na 2SO 4 aqueous solution electrolyte. The prepared materials remained amorphous until 300 °C and then transformed to crystalline α-MnO 2 at 400 °C. A specific capacitance of approximately 242 F/g was obtained by annealing at 200 °C. Annealing temperatures higher than 200 °C resulted in a decline of the specific capacitance. The specific capacitance of MnO 2 annealed at 200 °C remained constant up to 400 cycles.