Electrochemical processes suffer from a number of challenges that needs to be overcome for widespread industrial adaptation. The need for an excess amount of inert supporting electrolyte in conventional three electrode set-ups with a single electrolyte medium makes synthetic applications uneconomical in both resource and sustainability aspects, and adds further complexities when the resulting product needs to be purified from the mixture which may also include the electro-catalyst. From an electro-analytical stand-point, altering the sample with the addition of high concentrations of electrolyte salt can have unpredictable chemical effects which may be difficult to account for in the analysis. The following results of the thesis addresses these issues by i) utilising triple-phase boundary systems where the electro-active species are kept in a separate phase from the source of electrons and ions, ii) introducing methods of heterogenising the electro-catalyst from the reaction mixture by immobilising in immiscible oils or polymers of intrinsic microporosity, and iii) offer practical application of such systems through the use of economical and technically unsophisticated methodologies. In the introduction the concept of an Integrated Chemical System is introduced where components with different functions can be synergistically combined and arranged to achieve a more complex output. In the context of electrochemistry, modifying electrodes with materials to add or improve activity, stabilise performance and to substitute more expensive materials, is desirable for enhanced control over the activity of an electrode. The first chapter begins with a general overview of various electrode modification strategies pioneered throughout the last few decades as an introductory narrative for the approach taken in the thesis. Integrated Chemical Systems synthesized and investigated in the thesis are as follows. In chapter 3, electrospun carbon nanofiber based triple-phase boundary systems are utilised for ion-transfer voltammetry across the liquid-liquid interface. Chapter 4 introduces a more conveniently prepared carbon microsphere-polystyrene composite, where the carbon is mechanically held together into a porous structure by an electrically insulating polymer binder. The porous carbon structure is demonstrated to be an effective host for organic oil analysis, under a triple-phase boundary set-up. Chapter 5 is also a study of a carbon-polymer of intrinsic microporosity composite, the polymer functions as a binder as well as a porous host for electrocatalytic guest molecules. Chapters 6 and 7 presents a novel hydrodynamic technique and its use in modulating mass transport in solution, which can be used as a diagnostic tool to study electrode processes at both modified and unmodified electrodes. Chapter 7 demonstrates the method’s utility through a mechanistic analysis of the organic free radical catalyst utilised in chapter 5. It is the hoped that the series of studies presented in the thesis addresses the issues with electrochemical processes at least in part through utilising economic materials and simple methodologies. Whilst the final outcome and devices presented are not fully optimised, they demonstrate a proof-of-principle of the main advantages of employing the modified electrodes. In future, better materials are needed to address the weaknesses of the composites investigated in the thesis to extract the full benefits offered by the electrochemical approach of chemical synthesis and analysis.
|Date of Award||6 Jun 2016|
|Supervisor||Frank Marken (Supervisor)|