MnO₂-embedded-in-mesoporous-carbon-wall structure for use as electrochemical capacitors

We present an in situ reduction method to synthesize a novel structured MnO₂/mesoporous carbon (MnC) composite. MnO₂ nanoparticles have been synthesized and embedded into the mesoporous carbon wall of CMK-3 materials by the redox reaction between permanganate ions and carbons. Thermogravimetric analysis (TG), X-ray photoelectron spectrum (XPS), X-ray diffraction (XRD), nitrogen sorption, transmission electron microscopy (TEM), and cyclic voltammetry were employed to characterize these composite materials. The results show that different MnO₂ contents could be introduced into the pores of CMK-3 treated with different concentrations of potassium permanganate aqueous solution, while retaining the ordered mesostructure and larger surface area. Increasing the MnO₂ content did not result in a decrease in pore size from the data of nitrogen sorption isotherms, indicating that MnO₂ nanoparticles are embedded in the pore wall, as evidenced by TEM observation. We obtained a large specific capacitance over 200 F/g for the MnC composite and 600 F/g for the MnO₂, and these materials have high electrochemical stability and high reversibility.