Behaviour of poly(pyrrole) and poly(N-methylpyrrole) electrodes in acetonitrile

The impedance of poly(pyrrole) (PP) and poly(N-methylpyrrole) (PMP) films on platinum in an acetonitrile, LiClO4 solution has been measured. At potentials more positive than a characteristic value, the electrodes exhibit porous behaviour and the impedance is determined by the double-layer capacitance and the solution resistance inside the pores. At more negative potentials, the PP and PMP electrodes behave like flat-plate electrodes and two impedance contributions can be distinguished, i.e. a material contribution (material resistance and material capacitance) and a contribution from the interphase polymer-electrolyte (faradaic resistance and double-layer capacitance)