Study of molten Li₂Co₃ electrolysis as a method for production of carbon nanotubes

Abstract

The production of carbon nanotubes (CNTs) by electrolysis in molten Li₂CO₃ was investigated by studying the effect of the electrolyte, temperature of the electrolyte and cathodic overpotential. Cyclic voltametry clearly shows that instead of the expected Li discharge of the cathode as a first reaction, some early electrochemical reaction starts at a potential of –0.1 V, as a result of which, instead of the expected process of intercalation into the graphite lattice and CNTs formation, deposition of carbon occurs with the graphite cathode acting as the substrate. The carbon deposit obtained during the process of electrolysis together with the solidified salt, after dissolving in water, filtering and drying, was inspected with scanning electron microscopy (SEM). The results show that, among the observed structures and impurities, there are no CNTs. The morphology of the product is different from others previously observed, with a shape like sheets of flowers, and very small nano-balls. The impurities are metal particles from the salt and the impurities originating from the salt. For better understanding and confirmation of these result, cyclic voltametry and electrolytic deposition of carbon on a molybdenum electrode was also investigated. Molten LiCl was used as a base electrolyte with adding of 1, 5 and 10 % of Li₂CO₃. SEM observations and cyclic voltammograms confirm that under those conditions a process of carbon deposition occurs.