Method for manufacturing vertically aligned carbon nanotubes, and electrochemical capacitors using these nanotubes as electrodes

A method for preparing a composite that comprises vertically aligned carbon nanotubes (VACNTs) on a substrate and disorganized additional carbon with graphitic domains deposited on an external surface of the nanotubes, the method comprising chemical decomposition of a carbon-source gas in a reactor comprising a heated enclosure and growth of the VACNTs and graphitic domains on a substrate, in the presence of a catalyst, wherein:

• a gaseous phase comprising the carbon source and catalyst precursor is injected continuously into the heated enclosure at a temperature of between 580° C. and 630° C. and at a pressure of between 0.5 bar and 1.5 bar,
• the catalyst precursor comprises ferrocene,
• the disorganized additional carbon comprises the graphitic domains and has a degree of semigraphitic organization in which a width ratio between band D and band G in a Raman spectrum of the VACNTs is greater than 2.0,
• the gaseous phase injected into the enclosure comprises acetylene as a source of carbon, toluene as a carrier gas for the catalyst precursor, hydrogen, and argon as an inert gas, and
• the growth of the VACNTs and the deposition of the disorganized additional carbon take place a single-step chemical vapor deposition process.