Ion Transfer Dynamics of Polyaniline and Its Derivatives in Energy Storage and Water Purification

This thesis concerns the electrochemistry of electroactive conducting polymer films in novel ionic liquid media of relevance to energy storage devices and in aqueous media for water purification. The processes taking place at the interfaces of the electrolytes and modified electrodes are important for improving the performance of electrochemical devices. Understanding physical and chemical behaviours of both components and their interfacial dynamic are the aims of this thesis. Polyaniline (PANI), its derivatives and copolymer modified electrodes were deposited with a combination of electrochemical (cyclic voltammetry) and acoustic wave (EQCM) measurement. The optical, electrochemical and morphological behaviours of the resulting films were characterised. Quartz crystal impedance analysis was for the first time used to identify deviations in liquid behaviour from Newtonian, depending on temperature. Ion exchange dynamics of PANI modified electrode in deep eutectic solvents (DES) was used to shed light on supercapacitor applications. Various aspects of the behaviour of PANI films exposed to DES media in the potential range corresponding to p-doping were identified. The rate limiting process, different switching processes and performance of resulting films depend not only on the film coverage but also on the growth conditions. PANI films cycled in non-aqueous media for supercapacitor applications were also used in non-acidic medium for the Electrically Switched Ion Exchange (ESIX) process. The concept is that PANI oxidation is accompanied by fluoride uptake in neutral solution and then eliminates fluoride into a different aqueous acidic waste stream. The mechanism and fundamentals of this concept were monitored by using the EQCM.