Synthesis of microsphere silicon carbide/nanoneedle manganese oxide composites and their electrochemical properties as supercapacitors

Synthesis of microsphere silicon carbide/nanoneedle MnO₂ (SiC/N-MnO₂) composites for use as high-performance materials in supercapacitors is reported herein. The synthesis procedure involves the initial treatment of silicon carbide (SiC) with hydrogen peroxide to obtain oxygen-containing functional groups to provide anchoring sites for connection of SiC and the MnO₂ nanoneedles (N-MnO₂). MnO₂ nanoneedles are subsequently formed on the SiC surface. The morphology and microstructure of the as-prepared composites are characterized via X-ray diffractometry, field-emission scanning electron microscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy. The characterizations indicate that MnO₂ nanoneedles are homogeneously formed on the SiC surface in the composite. The capacitive properties of the as-prepared SiC/N-MnO ₂ electrodes are evaluated using cyclic voltammetry, galvanostatic charge/discharge testing, and electrochemical impedance spectroscopy in a three-electrode experimental setup using a 1-M Na₂SO₄ aqueous solution as the electrolyte. The SiC/N-MnO₂(5) electrode, for which the MnO₂/SiC feed ratio is 5:1, displays a specific capacitance as high as 273.2 F g^-1 at 10 mV s^-1.