Impedance analysis of polyaniline prepared on interdigitated array electrode under direct current polarization potential

A new method, ‘biased impedance analysis (BIA)’, was proposed for in situ measurements of a.c. impedance of polyaniline (PAn) film during and after deposition on an interdigitated array (IDA) electrode under d.c. bias (polarization) potential. With this BIA we designed two types of experiments: one was BIA under cyclic voltammetric (CV) sweep in 1 M HCl on PAn films polymerized via a constant current (40 μA cm−2) mode in properly buffered media at different pH (below 1.7) but with the same chloride ion concentration ([Cl−] = 1 M); the other was BIA on PAn films during and after constant potential (+ 0.75 V) mode polymerization in 1 M HCl or 1 M HClO4 both at pH = 0.2. As to the effect of pH of the polymerization media, the PAn film obtained at high pH had narrow conductive potential range during CV scans between −0.1 and 1.0 V as compared with that obtained at low pH. The PAn film obtained in HClO4 exhibited faster and larger impedance increase (than that polymerized in HCl), leading to a poorer performance upon potential scanning especially from the conductive-oxidation state at high potential to the insulating-reduction state at low potential.