Study of electrode kinetics

Thesis

This thesis reports the use of Tafel analysis in the study of electrode kinetics from both theoretical and experimental perspectives.

During electrochemical measurements, any changes in temperature cause changes in diffusion coefficient of the species, the electrochemical rate constant and the equilibrium potential. Concequently, the improtance of temperature control in electrochemical systems is first investigated. When and how thermally induced convective flows in bulk solution influence the votlammetric behaviour are presented in Chapter 3.

Chapters 4 and 5 theoretically discuss what fraction of a voltammetric wave is appropriate to use as the Tafel region for accurate analysis under linear, quasi-steady-state and steady-state mass-transport regimes for an irreversible one-electron transfer process. The measured transfer coefficient is found to deviate significantly from its true value as a function of potential due to the mass-transport limitation at high overpotentials. If and how a simple analytical mass-transport correction using a plot of ln |¹_I-¹_Ilim| against potential can be used to improve the measurement of transfer coefficient is investigated. The methodology of measuring transfer coefficient is further employed in the electrochemical characterisation of a single microband electrode with unknown dimensions (Chapter 6). Such Tafel analysis is applied to an experimental study where the intrinsic surface quinones on carbon substrates can catalyse Fe^2+/3+ redox reaction evidenced by a potential dependent transfer coefficient (Chapter 7).

Last but not least, a new simulation techinique is developed in Chapter 8 to extract the kinetic information from experimental voltammograms for electrodes under both radial and liner regimes on the basis of the prior knowledge of the physical parameters defining the system, most importantly the diffusion coefficient, analyte concentration and electrode radius.

Authors: Li, D

• DOI: 10.5287/ora-j1x1qpkzk
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: Surface quinone; Band electrode; Thermal convection; Mass transport corrected Tafel analysis; Microelectrode; Tafel analysis; Electrode kinetics; Mass transport; Electrocatalysis
• Subjects: Fundamental electrochemistry; Electroanalytical chemistry; Electrochemistry