Growth and functionalization of CNTs on stainless steel electrodes for supercapacitor applications

Vertically aligned carbon nanotubes (VA-CNTs) were grown on stainless-steel (SS) substrates by RF plasma enhanced chemical vapour deposition (PECVD). Adhesion of the CNTs to the substrate improves after treating the SS substrates with HF acid and adding an Al2O3 layer of 20 nm that is required to support the metal catalyst. An optimal distribution of catalyst nanoparticles was required for a satisfactory CNT growth. In addition, the effect of a nitrogen plasma post-treatment of the obtained CNTs on the electrochemical properties of the electrodes has been investigated. SEM and Raman characterization provided morphological and structural information about the CNTs grown before and after the plasma treatment. Electrochemical measurements showed that the specific capacitance of the nanotubes increases from 44 to 137 Fg(-1) for untreated and nitrogen plasma treated CNTs, respectively, in 0.1 M Na2SO4 aqueous solution.