The effect of salts on the electrochemical polymerization of aniline

Aniline is electrolysed by repeated potential cycling between 0 and 1.1 V (versus SCE); a current plateau instead of a current peak is observed on the I-E curve for the first cycle during electrolysis of aniline in aqueous acid solution in the presence of NaCl. The occurrence of the current plateau plays an important role in extending the potential range of electrolysis of aniline at a high rate. The polymerization rate of aniline in a solution containing a given HCl concentration increases with increasing concentration of sodium chloride; the potential range of the intermediate generated at the disk electrode is also extended with increasing concentration of NaCl. The potential necessary for the formation of the soluble intermediate is at least 0.75 V. The hydrochloric acid concentration necessary for an autocatalytic polymerization of aniline decreases from 0.6 to 0.4 M in the presence of NaCl. The conductivity of polyaniline prepared in a solution containing 0.2 M aniline, 0.4 M HCl and 1 M NaCl is about 30 times higher than that of polyaniline prepared in a solution containing 0.2 M aniline and 0.4 M HCl. The oxidation potential of aniline in the presence of the salts shifts toward negative potentials, depending on the ionic radius of cations and the concentration of the different salts.