Fabrication and Plasma Treatment of Carbon Nanotubes on Sputtered Cobalt for Electrodes of Electrochemical Capacitors

Abstract

A cobalt (catalyst) is sputtered at different time levels on graphite foil on which carbon nanotubes are subsequently directly grown by chemical vapor deposition (CVD). Next, carbon nanotubes are modified by RF (radio frequency) oxygen-plasma at different volume flow rates of oxygen and then immersed in nitric acid solution. The longer Co sputtering time led to the thicker Co film thickness. Higher specific capacitance of 140.2 F g⁻¹ is obtained under a certain condition (Co sputtering time=15 min and flow rate of oxygen=30 cm³ min⁻¹). This shows good specific capacitance. Furthermore, the higher flow rate of oxygen caused the higher carbonyl functional group (C=O), thus leading to higher specific capacitance.