MnOx/carbon nanotube/reduced graphene oxide nanohybrids as high-performance supercapacitor electrodes

Abstract

Nanohybrids consisting of both carbon and pseudocapacitive metal oxides are promising as high-performance electrodes to meet the key energy and power requirements of supercapacitors. However, the development of high-performance nanohybrids with controllable size, density, composition and morphology remains a formidable challenge. Here, we present a simple and robust approach to integrating manganese oxide (MnOx) nanoparticles onto flexible graphite paper using an ultrathin carbon nanotube/reduced graphene oxide (CNT/RGO) supporting layer. Supercapacitor electrodes employing the MnOx/CNT/RGO nanohybrids without any conductive additives or binders yield a specific capacitance of 1070 F g−1 at 10 mV s−1, which is among the highest values reported for a range of hybrid structures and is close to the theoretical capacity of MnOx. Moreover, atmospheric-pressure plasmas are used to functionalize the CNT/RGO supporting layer to improve the adhesion of MnOx nanoparticles, which results in theimproved cycling stability of the nanohybrid electrodes. These results provide information for the utilization of nanohybrids and plasma-related effects to synergistically enhance the performance of supercapacitors and may create new opportunities in areas such as catalysts, photosynthesis and electrochemical sensors. Researchers have discovered how to triple the energy storage of flexible graphite supercapacitors by using flower-like nanoparticles. Carbon-based nanomaterials are widely used as supercapacitor electrodes because their surfaces can hold and release charges quickly. But to improve energy storage densities, group of collaborators based in Australia and the USA led by Kostya (Ken) Ostrikov, with the principal contribution by Zhao Jun Han investigated ways to combine carbon electrodes with manganese oxide, a metal compound with an exceptional theoretical capacitance. They developed a new support —a film of carbon nanotubes and reduced graphene oxide on graphite paper — that could control the size, thickness and morphology of electrodeposited manganese oxide nanoparticles. Experiments revealed that certain porous, flower-like nanostructures dramatically boosted supercapacitance by fixing firmly to the carbon film and enhancing adsorption of surface ions. Predeposition plasma treatments also helped the hybrid electrode adhere together for better charge cycling stability. This work reports a simple and robust approach to integrate MnOx nanoparticles onto flexible graphite paper using an ultrathin CNT/RGO supporting layer. Supercapacitor electrodes employing the MnOx/CNT/RGO nanohybrids without any conductive additives or binders yielded a high specific capacitance. The cycling stability of the nanohybrid electrodes was further improved through functionalizing the CNT/RGO supporting layer with atmospheric-pressure plasmas, demonstrating the synergistic use of nanohybrids and plasma-related effects for enhanced device performance.