The electrochemical reduction of CO₂ in acetonitrile on copper

This thesis explores the electrochemical reduction of CO₂ in acetonitrile using copper electrodes, analysing how electrocatalyst and electrolyte parameters affect activity and selectivity. Key findings show how aprotic media differs to aqueous systems, including advantageous hydrogen evolution reaction (HER) limitation and enhanced CO₂ reduction efficiency.
Chapter 1 introduces the challenges of climate change and highlights electrochemical CO₂ reduction (CO₂RR) as a promising solution. The limitations of aqueous systems are discussed, including low CO₂ solubility and concomitant HER, as well as the potential of non-aqueous alternatives and how each parameter influences the reaction.
Chapter 2 examines how copper nanostructures influence CO₂RR. Cu nanocubes were found to favour C₂₊ products and suppress HER, especially at low water content. However, CO production remains dominant due to strong acetonitrile-Cu interactions.
Chapter 3 investigates the role of tetraalkylammonium cations in CO₂RR. Larger cations inhibit HER, while smaller ones enhance oxalate or formate production, depending on water content. Spectroscopic evidence of adsorbed CO provides insights into the reaction mechanism.
Chapter 4 studies the impact of water, including the stabilisation of intermediates and improving kinetics, whilst excess water promotes HER. Controlling water levels is essential for optimising selectivity and efficiency.
Chapter 5 explores electrocarboxylation, demonstrating that the initial electron transfer location determines product selectivity, being influenced by functional groups and applied potential.
Chapter 6 employs multivariate data analysis to identify key variables like water content, applied potential, and current density as critical for Faradaic efficiency. This offers deeper insights into the complex interplay of factors governing CO₂RR.