Applied potential limits for polypyrrole in a two-electrode device

The long term operation of two electrode all polymer devices requires a balance between extending the potential limits as far as possible to give full oxidation and reduction of the CEPs, while ensuring that the potentials at which overoxidation occurs are not reached. In this work, the 'true' potential (vs Ag/AgCl) at one electrode in a two-electrode cell was determined while applying a range of potential differences between the two polypyrrole electrodes. At an applied potential of plus or minus 2 V, only slight overoxidation of polypyrrole was evident at either electrode. However, for long term applications of polymer films it was shown that plus or minus 1.5 V would be more suitable. This potential difference was applied over an extended period in a series of potential steps to a two electrode device in a propylene carbonate solution and found to have no deleterious effects on the polymer electrodes. It was also shown that this potential difference was sufficient to fully oxidize and reduce PPy both in a supporting electrolyte solution and as a component of a two-electrode solid state device.