E, Peisan (2016) Nanostructured electroactive materials : applications in electroanalysis and electrocatalysis. PhD thesis, University of Warwick.

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Abstract

Carbon materials, including single-walled carbon nanotubes (SWNT) and graphene, have gained great interest in electrochemistry. The advantages of carbon electrodes include chemical stability, biocompatibility, low background currents and good electrical conductivity. With the increasing importance of carbon electrode materials for biological and energy application, the systematic investigation and new applications is mandatory.

SWNT networks, with different densities, are firstly investigated using microscale capillary electrochemical (EC) methods. Pristine high density (HD) SWNT networks are shown to exhibit more facile electron transfer (ET) for dopamine (DA) electro-oxidation and are less susceptible to blocking by reaction products when compared to low density (LD) SWNT networks. Acid treatment of SWNT networks results in an enhancement of electrode kinetics and a reduction in their susceptibility to surface fouling. Further, a comparison is made between SWNT electrodes, with different densities and a commercial screen printed carbon electrode (SPCE), for the oxidation of ferrocenecarboxylic acid (FcCOOH) in complex aqueous media (polyethylene glycol (PEG) and albumin), to mimic conditions in which diagnostic devices might be used. SWNTs exceed the performance of SPCEs, with a detection limit that is 3 orders of magnitude lower. Finally, a Ni(OH)2 nanoparticles (NPs) modified SWNT network is employed for the methanol oxidation reaction (MOR) and the ethanol oxidation reaction (EOR), showing improved ET processes with ~2.8 kA g-1 for MOR and ~3.7 kA g-1 for EOR, which are much higher than recent reports using other nanostructured catalysts.

A fundamental understanding of the structure-activity of “blistered” highly oriented pyrolytic graphite (HOPG), produced by electro-oxidation in HClO4, is obtained using scanning EC cell microscopy (SECCM) coupled with multi-microscopy techniques. The disordered sp2 carbon structure of the blister catalyzes the electro-oxidation of hydrazine compared to the basal surface. In this study, a potential sweep at each pixel of pre-defined scan area is recorded, providing potentiodynamic data with high resolution.

To demonstrate that the approaches are generally applicable, a fundamental study of the redox activity for Li2O2 product (toroidal and layer structure) in dimethyl sulfoxide (DMSO) non-aqueous media, is undertaken. A unique gel polymer organic electrolyte (polymer matrix, cross linker and organic electrolyte) is employed in a dual barrel nanopipette and the SECCM approach is carried out with cyclic voltammetry (CV) measurements performed at every pixel of a scan. The Li2O2 toroids outperforms the Li2O2 layer structure with a 9 times increase in the current response and ca. 80 % of charge efficiency. This work provides valuable information with regards to cathode materials for effective Li-air battery.

Item Type:	Thesis or Dissertation (PhD)
Subjects:	Q Science > QD Chemistry
Library of Congress Subject Headings (LCSH):	Electrochemistry, Carbon nanotubes -- Electric properties, Nanostructured materials -- Electric properties, Electrochemical analysis, Electrocatalysis, Scanning electron microscopy
Official Date:	September 2016
Dates:	Date Event September 2016 Submitted
Institution:	University of Warwick
Theses Department:	Department of Chemistry
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Unwin, Patrick R. ; Macpherson, Julie V.
Sponsors:	University of Warwick. Chancellor International Scholarship
Format of File:	pdf
Extent:	xxiii, 195 pages : illustrations, charts
Language:	eng

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