Electrochemical deposition of nanostructured manganese oxide on hierarchically porous graphene-carbon nanotube structure for ultrahigh-performance electrochemical capacitors

Abstract

A 3D graphene sheet-carbon nanotube (GS-CNT) structure with a good wetting property, high porosity, and large surface area is homogeneously deposited with active amorphous manganese oxide (a-MnOx) by potentiodynamic deposition. The flowery a-MnOx nanostructure with ultra-slender petals (ca. 5-8 nm) on the framework of hierarchically porous GS-CNT matrix not only enables nearly full utilization of a-MnOx but also retains sufficient conductivity and porosity for the high-rate charge-discharge application. The use of a-MnOx on the 3D GS-CNT material produces a specific capacitance of MnOx of 1200 F g-1 which is much-higher than that of a pure a-MnOx electrode (CS,Mn = 233 F g-1). The specific energy and specific power of a-MnO x/GS-CNT are respectively as high as 46.2 Wh kg-1 and 33.2 kW kg-1, revealing that our work conceptually provides a way to produce porous structures composed of graphene, carbon nanotubes, and various electroactive materials for high-performance energy storage devices. © 2012 Elsevier B.V. All rights reserved.