Electroanalytical evaluation of redox catalysts for organic electrosynthesis: a case study of nitroxyl-mediated alcohol oxidation

Abstract

Electrosynthesis is an emerging and sustainable method for organic synthesis, offering precise reaction control, eliminating the need for stoichiometric chemical oxidants and reductants, and allowing access to novel chemical intermediates in situ. However, its broader adoption is hindered by challenges in accurately understanding electrocatalyst performance. Factors such as mass transport effects, electrode materials, cell configurations, and the presence of co-reactants introduce variability that complicates the rational design and optimisation of electrosynthetic processes.
This work comprises a series of studies aimed at improving the understanding and application of organic electrosynthesis with a focus on nitroxide radical-mediated alcohol oxidation in aprotic solvents. The first study, Chapter 2, explores the electrochemical properties of polymer-immobilised piperidinyl oxyl (PIPO), demonstrating its potential as a homogeneous and immobilised electrocatalyst, and providing insights into its redox behaviour and catalytic performance. Chapter 3 evaluates the applicability of kinetic benchmarking frameworks, commonly used in molecular electrocatalysts for producing energy carriers, for organic electrosynthesis. By extracting key catalytic parameters, this study highlights the extent to which existing models can predict real-world reaction outcomes and the considerations that must be made when performing such analyses. Chapter 4 investigates the impact of separator materials in divided electrochemical cells, revealing the critical role of membranes in improving selectivity and efficiency in non-aqueous electrosynthesis and offering insights into their selection process. Finally, Chapter 5 applies constant current chronopotentiometry and cyclic voltammetry to systematically probe the influence of applied current density on reaction outcomes, establishing a rational approach to current selection beyond trial-and-error optimisation.
By integrating electroanalytical techniques with practical electrosynthetic studies, this work advances the understanding of electrocatalyst performance, cell design, and reaction control in organic electrosynthesis. The findings contribute to the development of more scalable and reproducible electrochemical methodologies, supporting the broader adoption of electrosynthesis as a key technology for sustainable chemical manufacturing.

Thesis is embargoed until 31 July 2026.

Date of Award	Jul 2025
Original language	English
Awarding Institution	Queen's University Belfast
Sponsors	Engineering and Physical Sciences Research Council
Supervisor	Paul Kavanagh (Supervisor) & Mark Muldoon (Supervisor)