Intercalation of sodium and lithium into graphite as a first stage in an electrochemical method for producing carbon nanotubes

A cyclic voltammetry method is used to show that the process of reduction of sodium (and, possibly, lithium) out of melts of corresponding chlorides on the molybdenum, glassy-carbon, and graphite electrodes is complicated by the process of dissolution of the corresponding alkali metal in the melt. A notion called reversibility of material balance is introduced. The notion reflects the ratio of the amount of substance that undergoes oxidation in the anodic half-cycle of a voltammetric curve to the amount of substance that is deposited in the cathodic half-cycle of the curve. The adsorption of sodium and lithium on glassy carbon and graphite plays an important role in the process of reduction, leading to an increase in the reversibility of the process. This is pronounced especially strongly at potential scan rates below 1 V s(-1). The sodium intercalation into graphite leads to a decrease in the reversibility of the process of reduction, the more so at potential scan rates below 0.03 V s(-1). However, the intercalation of lithium (probably because of its small atomic radius) does not exert practically any influence on the reversibility of process at the above potential scan rates.