Poly(o-toluidine) for carbon fabric electrode modification to enhance the electrochemical capacitance and conductivity

Capacitance and conductivity enhancements of activated carbon fabric employed as electrodes of electrochemical capacitors (ECs) were achieved by electrochemical deposition of conducting poly(o-toluidine) (POT). Potentiodynamic polymerization of o-toluidine onto the carbon in H2SO4 was employed for this carbon modification. The capacitance of the activated carbon was enhanced by superimposing the psuedocapacitance of poly(o-toluidine) onto the double-layer capacitance of the carbon. Deposition of polyaniline was also conducted for the purpose of comparison. With the presence of the electron-donating methyl group in the phenyl ring, poly(o-toluidine) is more effective than polyaniline in enhancing the capacitance of the carbon fabric. The specific capacitance of the electrodes increased with the amount of poly(o-toluidine) deposited and more than twice of that of the bare carbon can be achieved. However, the capacitance per unit weight of the deposited polymer decreased with the extent of deposition, probably due to an increase of the ion migration resistance that increasingly obstructs some polymer from the access of ions. The resistance of the carbon electrode was found to decrease upon polymer deposition, and this was found to be more significant with poly(o-toluidine) than with polyaniline. The low resistance resulting from poly(o-toluidine) deposition enabled the assembly of capacitors of relatively high power densities, more than three times of that of a capacitor with the bare carbon.