Assessment of Carbon Fibre (CF) and Carbon Nanotube (CNT) as Supercapacitor Electrode on Surface Activated Nickel Foam

Abstract

In present paper, an attempt has been made to compare the potential of two different carbon-based materials, Carbon Fibre (CF) and Carbon Nanotubes (CNT), as electrode materials. These two materials are compared against each other in terms of their dimensions, volume of deposition on Nickel foam and their performance under Cyclic Voltammetry (CV). It was observed that owing to the dimensions of the depositing material, CNT (nano-sized carbon) electrode reflected 5-fold increase in Brunauer-Emmett-Teller (BET) specific surface area as compared to CF (micro-sized carbon) electrode. When used as electrodes for CV, the CF showed a higher anode and cathode peak potential with negligible peak currents at both anode and cathode. The flat shape of the curve also indicated the same. On the contrary, CNT exhibited lower potential at ~0.1 V for both anode and cathode with higher anode and cathode peak currents. Thus, when comparing the duck shaped loop of CV it was observed that it was not wide enough to give better performance from the volume of the material deposited. Thus, to improve the current carrying capacity of the electrode, the Nickel foam was washed/activated using Nitric acid (NaOH) and then both materials deposited for comparison. It was observed that after activation, the anode and cathode peak currents for both CF and CNT increased significantly. The smaller of insignificant current value exhibited by CF before activation indicated that the volume of the material deposited was not sufficient to generate the current density. After activation, the volume of material increases, thereby reflecting as increased peak currents at slightly higher potentials. In case of CNT, though the anode and cathode potential remained same before and after activation, the cathode current improved by ~40% and anode current by ~80%. This improvement was analogous with the BET results, wherein the specific surface area of the material deposited on the foam increased after activation. This can be collectively attributed to the size of CNT (nano) and volume of material deposition on Nickel foam after activation. Thus, it was concluded that an electrode made of CNT and deposited on NaOH activated Nickel foam is a superior electrode material.