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Abstract: MnO2-pillared layered manganese oxide has been first fabricated by a delamination/reassembling process followed by oxidation reaction and then by heat treatment. The structural evolution of MnO2-pillared layered manganese oxide has been characterized by XRD, SEM, DSC-GTA, IR and N2 adsorption-desorption. MnO2-pillared layered manganese oxide shows a relative high thermal stability and mesoporous characteristic. The layered structure with a basal spacing of 0.66nm could be maintained up to 400°C. The electrochemical properties of the synthesized MnO2-pillared layered manganese oxide have been studied using cyclic voltammetry in a mild aqueous electrolyte. Sample MnO2–BirMO (300°C) shows good capacitive behavior and cycling stability, and the specific capacitance value is 206Fg−1. [Copyright &y& Elsevier]

Abstract: Ruthenium oxide/graphene (RuO2/GR) hybrid materials for high performance electrochemical capacitor have been prepared by a solution-phase assembly technology between RuO2 nanosheets and GR nanosheets at room temperature. The high dispersion of RuO2 and GR nanosheets maintains a high structural stability for the hybrid material, and causes an obvious synergistic effect between the RuO2 and GR nanosheets. A specific capacitance of 479 F g−1 has been obtained for the hybrid material with RuO2 mass content of 40% (abbreviated as RuGR46), and a high specific capacitance of 998 F g−1 obtained for RuO2 in the electrode. The utilization of RuO2 in the RuGR46 hybrid material increases by adding GR, and the capacitance of RuGR46 is quite comparable to that of the pristine RuO2·xH2O while 60 wt% of RuO2 can be saved. A symmetrical electrochemical capacitor based on the RuGR46 electrode is assembled with 0.5 mol L−1 H2SO4 solution as the electrolyte in a voltage of 0–1.2 V. It can give a high energy density of 20.28 Wh kg−1 at a power density of 600 W kg−1. Moreover, it presents a high power density (14.03 Wh kg−1 at 12 kW kg−1) and excellent cycle performance. [Copyright &y& Elsevier]

Abstract: The graphene–manganese oxide hybrid material has been prepared by solution-phase assembly of aqueous dispersions of graphene nanosheets and manganese oxide nanosheets at room temperature. The morphology and structure of the obtained material are examined by scanning electron microscopy, transition electron microscopy, X-ray diffraction and N2 adsorption–desorption. Electrochemical properties are characterized by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy. An asymmetric electrochemical capacitor with high energy and power densities based on the graphene–manganese oxide hybrid material as positive electrode and graphene as negative electrode in a neutral aqueous Na2SO4 solution as electrolyte is assembled. The asymmetrical electrochemical capacitor could cycle reversibly in a voltage of 0–1.7V and give an energy density of 10.03Whkg−1 even at an average power density of 2.53kWkg−1. Moreover, the asymmetrical electrochemical capacitor exhibit excellent cycle stability, and the capacitance retention of the asymmetrical electrochemical capacitor is 69% after repeating the galvanostatic charge–discharge test at the constant current density of 2230mAg−1 for 10,000 cycles. [Copyright &y& Elsevier]