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Title: Amperometric gas sensing using room temperature ionic liquids
Author: Li, Peilin
ISNI:       0000 0004 6346 4902
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2015
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The work presented in this thesis aims at overcoming the limitations of current amperometric gas sensors. The applicability of room temperature ionic liquids to be employed as potential electrolyte in gas sensors has been examined. This thesis demonstrates that RTILs have great potential to replace conventional electrolytes due to their wide electrochemical windows, negligible vapour pressure, inherent conductivity and sensitivity. A model to simulate the current response at porous electrodes has also been proposed to provide a theoretical support for the future application of porous electrodes in gas sensors. The results of these researches are summarised as follows: Chapter 1 introduces the fundamentals of electrochemistry which are employed throughout this thesis. Chapter 2 presents a comprehensive review of the history and recent development of amperometric gas sensors with their specific applications and limitations presented. Room temperature ionic liquids, microelectrodes and porous electrodes are also introduced in this chapter to initially discuss their potential for gas sensors. Chapter 4 studies the interaction between carbon dioxide and an imidazolium cation based RTIL. The solubility and diffusion coefficient are determined by the analysis of chronoamperometry using the Shoup and Szabo equation. A mechanism of the interaction between CO2 and the RTIL is proposed and validated by theoretical modelling. Chapter 5 focuses on O2 uptake in a phosphonium cation based RTIL. A mechanism of O2 reduction in this RTIL is proposed, reflecting a two electron reduction pathway. Proof-of-concept for this RTIL to be developed into a CO2/O2 dual sensor is confirmed with by experiments with CO2/O2 gas mixtures. Oxygen uptake in a series of alkylammonium cation based RTILs has been carried out as described in Chapter 6. The diffusivity of O2 in RTILs does not follow the Stoke-Einstein equation but broadly decreases as the viscosity increases. Chapter 7 proposes a theoretical model for the electrochemical behaviour at porous electrodes. Studies with two types of porous electrodes are employed and validate the applicability for this model to simulate the current response at porous electrodes.
Supervisor: Compton, Richard G. Sponsor: China Scholarship Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available