Charge Compensation Dynamics in the Redox Processes of Polypyrrole-Modified Electrodes

Electrochemical quartz crystal microbalance (EQCM) data combined with cyclic voltammetry were used to study the ionic exchange process in polypyrrole films prepared in sulfuric acid solution. A quantitative analysis of the results indicates a doping degree of 33% after polymerization and a high polymerization efficiency. Studies performed in monomer-free solutions of Na 2 SO 4, NaNO 3, and Cs 2 SO 4 show that both anions and cations are involved in the charge compensation process. The analysis of the ionic exchange is made using the integral quantities (charge, mass, number of moles, and molar fraction) and differential quantities (ionic fluxes and transport number). The results of such quantitative calculations are interpreted taking also into account the transfer of neutral species like solvent molecules and the physicochemical nature of the anions and cations involved in the redox process.