A novel core-shell multi-walled carbon nanotube@graphene oxide nanoribbon heterostructure as a potential supercapacitor material

A novel core-shell heterostructure with multi-walled carbon nanotubes as the core and graphene oxide nanoribbons as the shell (MWCNT@GONR), fabricated by the facile unzipping of MWCNTs with the help of microwave energy, was used as a supercapacitor (SC) electrode material. Graphene nanopowder (GNP) and multi-walled carbon nanotubes (MWCNTs) have also been applied as SC materials for comparison. A smooth surface and a tube-like structure are found for the GNP and MWCNTs, respectively, while for the MWCNT@GONR material, graphene oxide sheet structures are observed on both sides of central nanotube cores that retain their tube-like structure. The specific capacitance is much better for the SC electrode with the MWCNT@GONR (252.4 F g^-1) compared to the SC electrodes with commercial MWCNTs (39.7 F g^-1) and GNP (19.8 F g^-1), as determined using cyclic voltammetry (CV) at a scan rate of 50 mV s^-1, which is due to the defective edges of the nanostructures in the former. The SC electrode with the MWCNT@GONR also exhibits good stability and capacitance retention even after 1000 cycles of galvanostatic charge-discharge testing, indicating its potential as a SC material. CV, galvanostatic charge-discharge (GC/D) and electrochemical impedance spectroscopy (EIS) were applied to analyze the SC performance.