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Rhombohedral shaped MnCO 3 and its hybrid composite with in situ reduced graphene oxide (rGO) and multiwalled carbon nanotubes (MWCNT) have been synthesized by a simple and cost effective hydrothermal approach and examined as active material for supercapacitor application. The redox active MnCO 3 showed high specific capacitance of 185 F/g at 1.5 A/g in 1 M Na 2 SO 4 electrolyte accompanied by high cycle stability. The high utility of the pseudocapacitive MnCO 3 was achieved in its carbonaceous materials based hybrid composites exhibiting the maximum specific capacitance of 368 F/g and 357 F/g, respectively for the rGO-MnCO 3 and MWCNT-MnCO 3 composite at 1.5 A/g current accompanied by very high cycle efficiency of 96% and 97% specific capacitance retention over 1000 charge discharge cycle at 3 A/g. The high surface activity of the MnCO 3 along with the synergistic effect with highly conductive and high surface area porous rGO and MWCNT resulted in their high energy density of 51.11 Wh/kg and 49.58 Wh/kg, respectively at a power delivery rate of 750 W/kg suggesting both of them are competent to act as supercapacitor electrode material. [ABSTRACT FROM AUTHOR]

A unique and cost effective hydrothermal procedure has been carried out for the synthesis of hexahedron shaped a MnMoO4 and its hybrid composite with graphene using three different weight percentages of graphene. Characterization techniques, such as XRD, Raman and FTIR analysis, established the phase and formation of the composite. The electrochemical characterization of the pseudocapacitive MnMoO4 and the MnMoO4/graphene composites in 1 M Na2SO4 displayed highest specific capacitances of 234 F g-1 and 364 F g-1, respectively at a current density of 2 A g-1. Unlike many other pseudocapacitive electrode materials our prepared materials responded in a wide range of working potentials of (-)1 V to (+)1 V, which indeed resulted in a high energy density without substantial loss of power density. The highest energy densities of 130 Wh kg-1 and 202.2 Wh kg-1 were achieved, respectively for the MnMoO4 and the MnMoO4/graphene composite at a constant power delivery rate of 2000 W kg-1. The synergistic effect of the graphene with the pseudocapacitive MnMoO4 caused an increased cycle stability of 88% specific capacitance retention after 1000 consecutive charge discharge cycles at 8 A g-1 constant current density, which was higher than the virgin MnMoO4 with 84% specific capacitance retention. [ABSTRACT FROM AUTHOR]

In-situ hydrothermal method is employed to synthesize graphene/zirconium oxide composite from respective precursors graphene oxide and zirconium oxy-nitrate. In this method, the graphene oxide is reduced itself to graphene and simultaneously metal oxide gets anchor on the graphene sheets. A novel method is also developed for the preparation of vertically aligned tunable polyaniline on the graphene/zirconium oxide nanocomposite, which leads to achieve high surface area (207.1 m2 g−1), high electrical conductivity (70.8 S cm−1), high specific capacitance (1359.99 Fg−1 at 1 mV s−1), and high electrochemical performances as supercapacitor electrode materials. This vertically aligned conducting polymer gets easy contact with electrolyte ions and provides numerous redox active sites during charging and discharging. Moreover, such a simple and low cost assembly approach can be a pioneer for the large-scale production of various functional architectures for energy storage and conversions. [ABSTRACT FROM AUTHOR]

NiMnO3–nitrogen doped graphene composite has been synthesized by a simple hydrothermal method and its supercapacitor performance investigated. The composite exhibits a specific capacitance of 750.2 F g−1 in 1 M Na2SO4 at a scan rate of 1 mV s−1. Nitrogen insertion inside the carbon lattice plays a crucial role in the enhancement of the overall specific capacitance and its long-term stability. This reproducible and superior performance of NiMnO3–nitrogen doped graphene composite make it attractive as a candidate for energy storage materials. [ABSTRACT FROM AUTHOR]

Highlights: [•] Ni(OH)2, Ag deposited Ni(OH)2 and their composites with graphene were synthesized. [•] XRD, FESEM and TEM analyses confirmed the formation of the composites. [•] Ag deposition increases the pseudocapacitive utility of Ni(OH)2. [•] Ag@Ni(OH)2/graphene composite exhibited the best electrochemical behavior. [•] Ag@Ni(OH)2/graphene exhibited 496F/g specific capacitance at 1A/g current density. [Copyright &y& Elsevier]

Abstract: A new supercapacitor electrode material was prepared by the in situ oxidative polymerization of aniline in presence of graphene and transition metal. The structural property of the composites has been determined by Raman spectroscopy. The formation of the composites has been confirmed by field emission scanning electron microscopy and the high resolution transmission electron microscopy. The electrochemical performance of the electrode materials has been illustrated by cyclic voltammetry, electrochemical impedance spectroscopy and cyclic charge–discharge. The uniform structure together with the observed high conductivities afforded high specific capacitance and good cycling stability during the charge–discharge process when used as supercapacitor electrodes. A greater specific capacitance has been achieved in the case of cobalt doped PANI on graphene (Gr/Co/PANI) composites in comparison with HCl doped PANI on graphene composites. The Gr/Co/PANI composites showed highest specific capacitance of 989F/g at a scan rate of 2mV/s. The energy density of Gr/Co/PANI composites could reach 352Wh/kg at a power density of 1.581kW/kg. [Copyright &y& Elsevier]