Nickel oxide nanotube synthesis using multiwalled carbon nanotubes as sacrificial templates for supercapacitor application

A novel approach for the fabrication of nickel oxide nanotubes based on multiwalled carbon nanotubes as a sacrificial template is described. Electroless deposition is employed to deposit nickel onto carbon nanotubes. The subsequent annealing of the product in the presence of air oxidizes nickel to nickel oxide, and carbon is released as gaseous carbon dioxide, leaving behind nickel oxide nanotubes. Electron microscopy and elemental mapping confirm the formation of nickel oxide nanotubes. New chelating polyelectrolytes are used as dispersing agents to achieve high colloidal stability for both the nickel-coated carbon nanotubes and the nickel oxide nanotubes. A gravimetric specific capacitance of 245.3 F g^-1 and  an areal capacitance of 3.28 F cm^-2 at a scan rate of 2 mV s^-1 is achieved, with an electrode fabricated using nickel oxide nanotubes as the active element with a mass loading of 24.1 mg cm^-2.