Abstract
The concept of supporting electrolyte-free electrosynthesis embodies the core values of green waste-free chemistry based on renewable electricity. The geometry of interdigitated electrodes (IDE) can provide the possibility for ions to self-support transport between anode and cathode. Despite Girault's pioneering work on electrosynthesis using interdigitated arrays in the 1980s, further development in this field remained stagnant. With the increasing urgency of sustainability, the intrinsic properties of IDEs have once again attracted attention. The aim of this project is to obtain an understanding of species behaviour near the interdigitated electrode arrays in the absence of the supporting electrolyte, to provide guidance for the development of sustainable electrosynthesis.Chapter 1 introduces the sustainability concept in electrosynthesis, typically focusing on paired electrosynthesis. It also provides a brief overview to the interdigitated electrode arrays, including materials, fabrication, electrochemical fundamentals, and electrosynthesis application. The chapter concludes by outlining the aims of this project.
Chapter 2 introduces the experimental techniques used in the project, including the electrochemical measurements and characterisation methods.
Chapter 3 explores the electrochemical behaviour of the [Fe(CN)₆]³⁻/⁴⁻ redox couple on a commercial graphene foam IDE with 150 micrometer gap and 400 micrometer width. The generatorcollector experiment is designed to analyse the feedback on the counter electrode collected from the reduction of the oxidised species generated at the working electrode. The hysteresis effect occurring with/without the supporting electrolyte was compared. Furthermore, a classic biosensor material, Prussian blue, is observed to deposit on the electrode under high applied potential, and it shows sensing ability for H2O2. This study reveals that 150 micrometer is too wide for the supporting electrolyte-free operation, so the gap must be reduced to support the transport.
Chapter 4 utilized the one-electron transfer reaction of decamethylferrocene (FeCp2*) oxidation to study a platinum interdigitated electrode with 5 micrometer gap and 5 micrometer width. By comparing the three-electrode and two-electrode measurement configurations, and the system with/without the supporting electrolyte, this chapter discusses the concentration gradient across the interelectrode gap and the influence of the counter electrode during the electrolysis. The experimental results are combined with a finite element simulation (conducted by Dr Evaldo Batista Carneiro-Neto).
Chapter 5 continues the use of the same Pt-Pt IDE from the previous chapter, exploring the influence of the supporting electrolyte on the charge annihilation process in the inter-electrode gap. Cyclic voltammetry is performed in a solution of 1,1’- ferrocenedimethanol in methanol, both with and without supporting electrolyte. Reaction areas are analysed and simulated by finite element simulation (conducted by Dr Evaldo Batista Carneiro-Neto). Furthermore, an olefin hydrogenation reaction was conducted with the system. The conversion and product yield, which are confirmed by NMR spectroscopy, were compared between the configurations with and without supporting electrolyte.
Employing the same type of electrode, Chapter 6 focuses on paired electrosynthesis as an example to further explore the mechanism and utility. To achieve this, the electrolyte-free concept was combined with the “translation” from photocatalysis to electrosynthesis strategy proposed by Jensen. The reduction of 1, 2-dicyanobenzene was selected as the cathodic process, coupled with methanol oxidation as the anodic reaction. Density functional theory (DFT) calculations (conducted by Dr. Claire McMullin) were carried out alongside 1H-NMR to provide insight into the reaction mechanism.
Interdigitated microband electrodes enable efficient supporting electrolyte-free electrosynthesis through enhanced ion transport across anode and cathode via short electrode gaps and migration effects. Chapter 7 provides a summary of the work and key findings presented in this project and additionally offers an outlook for future research directions.
| Date of Award | 22 Jul 2026 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Frank Marken (Supervisor) & James Taylor (Supervisor) |
Keywords
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