Investigation of the applied potential limits for polypyrrole when employed as the active components of 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 conducting electroactive polymers (CEPs), while ensuring that the potentials at which overoxidation occurs are not reached. In this work, the “true” potential (versus Ag/AgCl) at one electrode in a two-electrode cell was determined whilst applying a range of potential differences between the two polypyrrole (PPy) electrodes. At an applied potential of ±2 V, only slight overoxidation of PPy was evident at either electrode. However, for long-term applications of polymer films, it was shown that ±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 (PC) solution and found to have no deleterious effects on the polymer electrodes. It was also shown that this potential difference was sufficient to fully oxidise and reduce PPy both in a supporting electrolyte solution and as a component of a two-electrode solid state device.