Cyclic Potential Sweep Electropolymerization of Aniline. The Role of the Anions in the Polymerization Mechanism

The cyclic potential sweep (CPS) method was applied to aniline electropolymerization in several strong acids (H2SO4, HNO3, HCl, HBF4, HClO4 and CF3COOH). It is mainly the type of anion that determines the morphology of polyaniline (PANI) deposits, promoting either a compact (BF-4, ClO4- and CF3COO-, class 1 anions) or an open structure (SO42-, NO3- and Cl-, class 2 anions), as suggested by the linear (class 1) or quadratic (class 2) dependence of deposition charges on number of cycles, scan rate and concentration of anilinium and anion, as well as by SEM analysis. From the potential dependence of deposition currents, PANI growth onto PANI is suggested to occur via adsorption of anilinium-anion ionic couples onto fully oxidized (pernigraniline) sites of PANI.