Electrosynthesis of conducting polymer nanocomposites at a polarisable liquid|liquid Interface and their applications in sensing and energy conversion and storage

This thesis provides a fundamental investigation into the electrosynthesis of free-standing poly(3,4-ethylenedioxythiophene) (PEDOT) composite thin films at the electrified interface between two immiscible electrolyte solutions (ITIES). First, the addition of gold nanoparticles (AuNPs) to the aqueous phase during the controllable electrosynthesis of PEDOT-AuNP films at the ITIES was investigated. Using electrochemical techniques such as cyclic voltammetry and chronoamperometry, a mechanism is proposed for this two-step electrosynthesis of interfacial PEDOT-AuNP. It was demonstrated that the interfacial electron transfer (IET) reaction between aqueous Ce(IV) and the organic EDOT monomer is mediated by AuNPs adsorbed at the ITIES. These AuNPs act as a ‘floating’ bipolar electrode (BPE) that assists the IET between organic monomers and the aqueous oxidant. The interfacial redox catalysis was recorded via nanoparticle impact experiments, in which we could observe multiple bursts of current upon addition of AuNPs, when the interfacial Galvani potential difference (∆o w𝜙) is biased positively enough (>0.2 V) for IET to happen. Extensive characterisation of the free-standing PEDOT-AuNP films was performed to analyse the morphology, composition, and electrochemical performance for the detection of dopamine.

A second synthesis route was studied to obtain PEDOT-AuNP thin films, using HAuCl4 as both the AuNP precursor and the electron acceptor (or oxidant). An in-depth explanation of the reaction mechanism is coupled with the recorded CVs for the electrochemical synthesis of PEDOT-AuNP in a 4-electrode configuration. Electrochemical characterisation of samples synthesised with HAuCl4 revealed a boost in conductivity and excellent performance as a dopamine sensor, reaching competitive limits of detection and sensitivity with state-of-the-art organic sensing devices. In the last section of this work, we explored the synthesis of nanocomposite films of PEDOT and multi-walled carbon nanotubes (MWCNT) for applications in energy storage devices. We used differently charged surfactants to prepare interfacial PEDOT-MWCNT films. Chemical and electrochemical characterisation revealed that the morphology of the films is highly affected by the surfactants used, therefore, influencing the charge storage capacity of the composites.