Optimal Synthesis of Manganese Oxide/Carbon Sphere Hybrids through a Chemical Deposition Process

Abstract

Manganese oxide/carbon sphere composites (MnO2/C) with suitable pore structure and coating layer have been synthesized through a self-limiting redox reaction between carbon spheres and permanganate at room temperature in neutral-pH solutions. The as-prepared composites were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and nitrogen adsorption techniques. Their capacitance performances were evaluated using both cycle voltammetry and galvanostatic charge-discharge methods. It was found that the specific capacitance of the composites firstly increased with the reaction time, and then it slightly decline and leveled off finally. The highest specific capacitance (170 F/g at a current density of 0.1 A/g) is obtained when the reaction time is 6 h.