Supercapacitor Electrodes from Tubes-in-Tube Carbon Nanostructures

Abstract

Supercapacitors occupying a region between batteries and dielectric capacitors have been touted as a solution to the mismatch between the fast growth in power required by devices and the inability of batteries to efficiently discharge at high rates. Here, we report the electrochemical characterization of tubes-in-tube carbon nanostructures to investigate their application to supercapacitors. The average specific capacitance has been calculated for the cyclic voltammetric plots at 50 mV/s. The tubes-in-tube multiwalled carbon nanotubes consisting of outer nanotubes with an average outer diameter of 50 nm and inner nanotubes with diameters in the range of 3–10 nm exhibit an average capacitance of 203 F/g and a specific capacitance of 315 F/g at 0.35 V in 0.5 mol/L H2SO4. Pure electrostatic attraction in the double layer and faradic reaction in the pseudocapacitor are responsible for the supercapacitance. The specific surface area of the samples characterized by a nitrogen isotherm at 77 K reveals that the higher supercapacitance can be realized by modifying the pore size, pore-size distribution, and conductivity of the carbon nanomaterials.

Sensitivity enhancement by carbon nanotubes: Applications to stem cell cultures monitoring

“…Since from Nernst equation it is not clear the parameters that can change adding carbon nanotubes onto the electrode, the hypothesis is that CNT could modify the electrostatic attraction in the double layer that is formed onto the interface between the electrode and the solution. That hypothesis was directly correlated with biosensing [6] and it can be a possible explanation of very promising properties belonged to MWCNT [7]. This layer effect changes the target molecule concentration close to electrode and concentration ratio changes in Nernst equation.…”

A review of electrode materials for electrochemical supercapacitors

“…As shown in Fig. 4, 116 redox peaks, which lead to a remarkable pseudocapacitance, come from the redox reaction (a faradaic process) of oxygenated groups on the surface of carbon nanostructures.…”

Carbon Nanotube Supercapacitors

“…As a result, combining the enhanced double-layer capacitance (due to the vertical alignment and well spacing of aligned CNTs and the plasma-etch-deduced end-tip-opening and defect formation) and the additional pseudocapacitance (due to the plasma-etch-deduced oxygenated functionalization), our aligned CNTs showed a remarkable capacitance (440 F/g) in the ionic liquid electrolyte. Previously, with the combined contribution of double-layer capacitance and pseudocapacitance, a high capacitance has been obtained for a templatesynthesized aligned CNT electrode (365 F/g) (Chen et al, 2004) and a tubes-in-tube CNT electrode (315 F/g) (Pan et al, 2007) in an aqueous H 2 SO 4 electrolyte. The improved capacitance of our aligned CNT electrode is believed to be due to its unique properties deduced from the plasma etching as discussed above.…”