Highly dispersible surface-unzipped multi-walled carbon nanotubes as binder-free electrodes for supercapacitor applications

Abstract In this study, highly dispersible unzipped multi-walled carbon nanotubes were successfully synthesized by chemical etching, and these nanotubes were used in the fabrication of binder-free electrodes by electrostatic spray deposition for supercapacitor applications. The chemical etching introduces oxygen-containing functional groups and the unzipping or exfoliation process of the multi-walled carbon nanotube sidewalls produces a form of graphene sheets, making them highly dispersible in a polar solvent and providing rich electrochemically active sites accessible to electrolyte ions under electrode state. The binder-free unzipped multi-walled carbon nanotube electrode delivered a specific capacitance as high as 133 F/g at a scan rate of 10 mV/s in a 1 M H₂SO₄ aqueous electrolyte. When the scan rate was increased to 500 mV/s, the specific capacitance of this binder-free electrode decreased slightly to 103 F/g, which is a 77% retention of the initial value at 10 mV/s. This highlights the competitive rate capability of this carbon-based electrode.