One-step large scale combustion synthesis mesoporous MnO2/MnCo2O4 composite as electrode material for high-performance supercapacitors

High quality MnO2/MnCo2O4 composites have been successfully synthesized by a one-step solution combustion process at 300 °C for 2 h in air. The effects of the amount of glycine and molar ratios of Mn/Co on phase composition, morphology and electrochemical properties of products were investigated. The prepared samples were characterized by X-ray diffraction, field-emission scanning electron microscopy, X-ray photoelectron spectroscopy, transmission electron microscopy and Brunauer-Emmett-Teller methods. Based on the optimum fuel/oxidizer molar ratios, the products transformed from spinel MnCo2O4 granular aggregates to a mixture of MnO2/MnCo2O4 composites with increase the molar ratios of Mn/Co. The electrochemistry performance of prepared different specimens were evaluated and compared through cyclic voltammetry and charge-discharge anylysis in 2.0 M KOH electrolytic solution. Electrochemical measurements showed that the MnO2/MnCo2O4 exhibited a optimal electrochemistry performance with the Mn:Co:glycine molar ratio of 3:4:31.5/9. The maximum specific capacitance of 497 F/g is achieved at a current density of 0.5 A/g (or 312 F/g at 10 A/g). The high electrochemical performance would be attributed to the numerous nanopores, large specific surface and synergistic effects of the MnO2 and spinel MnCo2O4.