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Title: Formation and electrocatalysis studies of nickel and iron sulfide catalysts using in situ XAS
Author: Islam, H.-U.
ISNI:       0000 0004 8497 782X
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2016
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X-ray absorption spectroscopy (XAS) is an atom specific characterisation technique. It is particularly useful for understanding dilute systems of short range order. When used in situ during reaction processes, the technique is a powerful tool to study the evolving local structure of materials. In this thesis, XAS is used to understand the synthesis, stability, and electrocatalytic activity of iron sulfides. A popular route to the synthesis of nanoparticulate sulfides is the solvothermal decomposition of transition metal dithiocarbamates. These single source precursors are typically dissolved in a coordinating solvent and heated rapidly. The coordinating solvent acts as a heat sink and capping agent but its role in each decomposition process is less understood. Here, it is shown through ex situ and in situ XAS that the coordinating solvent has significant effect on the starting material and decomposition process through coordination to the transition metal centre and reaction with the dithiocarbamate backbone. Case studies include the decomposition of zinc dimethyl, and nickel and iron diisobutyl dithiocarbamates in oleylamine. The solvothermal decomposition of iron or iron and nickel diisobutyl dithiocarbamate in the presence of thiuram disulfide results in the formation of Fe3S4 or NiFe2S4 nanoparticles. These inverse spinel structures are formed as hexagonal sheets with 001 and 111 surfaces which are predicted to be electrocatalytically active. The oxidation of the systems in electrolyte during cyclic voltammetry - a process that is thought to reduce catalytic activity - is investigated by in situ XAS.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available