Effects of the catalyst and substrate thickness on the carbon nanotubes/nanofibers as supercapacitor electrodes

• Published in: Physica scripta 2012-12, Vol.86 (6), p.65603-5
• Main Authors: Gao, Y, Pandey, G P, Turner, J, Westgate, C, Sammakia, B
• Format: Article
• Language: English
• Subjects: Capacitance; Capacitors; Carbon nanotubes; Catalysts; Electrodes; Iron; Scanning electron microscopy; Titanium
• ISSN: 0031-8949; 1402-4896
• DOI: 10.1088/0031-8949/86/06/065603

The different growth conditions of carbon nanotubes (CNTs)/carbon nanofibers (CNFs) which lead to different characteristics when used as supercapacitor electrodes are reported. A layer of SiO2 was coated onto the Si substrate and then a layer of Ti was evaporated as a current collector. CNTs/CNFs were synthesized on the Ti surface via a water-assisted chemical vapor deposition method at 800 °C and at atmospheric pressure utilizing iron (Fe) nanoparticles as catalysts, ethylene (C2H4) as the precursor gas and argon (Ar) and hydrogen (H2) as the carrier gases. The effects of different thicknesses of the catalyst (5 and 10 nm) and Ti substrate layer (10, 30 and 150 nm) on the specific capacitance of the CNFs were studied and the capacitance of the CNTs/CNFs-based device was dependent on CNT/CNF morphology of the CNFs that varied for different combinations of the catalyst and Ti layer thicknesses. The characterization of CNTs/CNFs was carried out using scanning electron microscopy, electron dispersive spectroscopy, transmission electron microscopy and electron diffraction. The specific capacitance was measured using cyclic voltammetry via a three-electrode system. The highest specific capacitance (60 F g−1) was obtained in the sample grown with 5 nm of Fe catalyst onto 10 nm of Ti substrate.