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Title: Au(hkl):surface X-ray diffraction studies at the electrochemical interface
Author: Fogg, Joshua James
ISNI:       0000 0004 7656 9041
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2019
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In-situ surface x-ray diffraction (SXRD) measurements have been performed to develop an increased understanding of electrocatalytic reactions and electrodeposition processes occurring on gold single crystal surfaces. The surfaces of gold exhibit a rich physical behaviour that is interesting not only from a structural perspective but also for applications in areas such as heterogeneous catalysis and electrocatalysis. The surface reconstructions of Au(111) and Au(100) have been found to undergo a potential dependent in plane surface compression in alkaline solution that is remarkably similar despite the underlying geometry. The compressibility is linked to the charge on the surface Au atoms with a simple free electron model. The surface compression and the reversible lifting of the reconstructions are determined by the interplay between surface charge and the adsorption of hydroxide species. Carbon monoxide adsorption is shown to supress both the potential-induced changes in surface compression and the lifting of the reconstruction leading to the promotion of electrocatalytic reactivity. Measurements of the Au(111)/Pb UPD system in acidic solution reveal a substitutional Au/Pb surface alloy of the ratio ~ 4:1 that forms at intermediate coverages of Pb during the stripping of Pb from the Au(111) electrode surface. Investigations into the adsorption of Acetonitrile (AcN) on the Au(111) electrode surface in sulphuric acid solution find that AcN has an enhancing effect on the adsorption of sulphate molecules. In the potential regions where sulphate is not adsorbed onto the Au(111) AcN is shown to weakly interact with the Au(111) electrode surface. The interaction between Cu and AcN ions in sulphuric acid solution and its effect on the Au(111)/Cu UPD process were investigated. AcN was shown to form a [Cu(C2H3N)4]+ complex with copper that enhances the the deposition of copper on the Au(111) surface and suppress the characteristic honeycomb (v3xv3)R30° structure in sulphuric acid.
Supervisor: Lucas, Christopher ; Grunder, Yvonne Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral