Electrochemical performance optimization of the polyaniline electrodeposited on ITO substrate

We have elaborated polyaniline films on ITO substrate (indium tin oxide), by electrochemical process in different electrolytes (HCl, H₂SO₄, HNO₃, and H₃BO₃), which allowed us to study the effect of the counter ion on electrochemical energy storage performances of polyaniline as electrode material in supercapacitors. The study of the different obtained films performances was carried out by cyclic voltammetry and galvanostatic charge-discharge method and is interpreted by the SEM technique. We found that there is a clear dependence on the specific capacitance of the counter ion. Justified by its porous structure, the PANI/ITO electrode doped with SO₄^2- has the highest specific capacitance, 57.3 mF/cm² at a current density of 0.2 mA/cm² and 64.8 mF/cm² at 5 mV/s. The deep analysis by Dunn's method allowed us to conclude that the faradic process dominates the energy storage in the case of PANI/ITO electrode elaborated in boric acid (99%). On the contrary, the capacitive character is the most contributory in the case of electrodes elaborated in H₂SO₄, HCl, and HNO₃. The study at different potentials (0.80, 0.85, 0.90, 0.95, and 1.0 V/SCE) from 0.2 M monomer aniline showed that the deposition at 0.95 V/SCE leads to higher specific capacitance (24.3 mF/cm² at scan rate 5 mV/s and 23.6 mF/cm² at 0.2 mA/cm²) with a coulombic efficiency of 94%. By varying the concentration of the monomer while keeping a potential fixed at 0.95 V/SCE, we also found that the specific capacitance increases with monomeric concentration.