Tubular graphene nanoribbons with attached manganese oxide nanoparticles for use as electrodes in high-performance supercapacitors

Graphene nanoribbons (GNRs) with tubular shaped thin graphene layers were prepared by partially longitudinal unzipping of vapor-grown carbon nanofibers (VGCFs) using a simple solution-based oxidative process. The GNR sample has a similar layered structure to graphene oxide (GO), which could be readily dispersed in isopropyl alcohol to facilitate electrophoretic deposition (EPD). GO could be converted to graphene after heat treatment at 300 °C. The multilayer GNR electrode pillared with open-ended graphene tubes showed a higher capacitance than graphene flake and pristine VGCF electrodes, primarily due to the significantly increased surface area accessible to electrolyte ions. A GNR electrode with attached MnO2 nanoparticles was prepared by EPD method in the presence of hydrated manganese nitrate. The specific capacitance of GNR electrode with attached MnO2 could reach 266 F g−1, much higher than that of GNR electrode (88 F g−1) at a discharge current of 1 A g−1. The hydrophilic MnO2 nanoparticles attached to GNRs could act as a redox center and nanospacer to allow the storage of extra capacitance.