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Surface studies of metal oxide catalysts and ultrathin films

Grinter, D.C.; (2011) Surface studies of metal oxide catalysts and ultrathin films. Doctoral thesis, UCL (University College London). Green open access

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Abstract

This thesis examines two important metal oxide systems: ultrathin CeO2(111) films on Pt(111), and carboxylic acids on TiO2 surfaces, both of which are significant for future energy research. The structure and growth of ultrathin films of CeO2(111) supported on Pt(111) have been studied with Scanning Tunnelling Microscopy (STM), Low Energy Electron Diffraction (LEED) and Auger Electron Spectroscopy (AES). The ultrathin films were grown in a number of ways and their growth mechanism, electronic structure, and domain boundaries were investigated using STM and STS. Atomically resolved STM images (filled and empty states) have been obtained on these ultrathin films permitting the identification of many defect structures. The behaviour of individual gold atoms at room temperature on ultrathin CeO2(111) films on Pt(111) has been investigated with STM. Simultaneous atomically resolved images of a gold adatom and the filled states of the ceria permitted the identification of two adsorption sites: (i) atop an oxygen atom and (ii) in a three-fold hollow site. The adsorption and reactivity of acetic acid on anatase TiO2(101) has also been investigated. It was found that at low coverage, acetic acid is observed to have a characteristic appearance consistent with a dissociative bidentate binding geometry to two neighbouring Ti5c sites. Deposition at elevated temperatures at saturation coverage yielded a (2 x 1) superstructure. The effects of heating, UV exposure, and tip pulsing were also investigated. STM has been used to investigate the adsorption and photo-reactivity of benzoic acid on rutile TiO2(110)(1 x 1) and (1 x 2). Benzoic acid binds to both surfaces dissociatively via a bridging geometry leading to a (2 x 1) overlayer on the (1 x 1) surface at saturation. Benzoate adsorbs between the added-rows of the (1 x 2) reconstruction leading to a (2 x 2) superstructure at higher coverage and demonstrated the important role of intermolecular interactions such as hydrogen bonding.

Type:Thesis (Doctoral)
Title:Surface studies of metal oxide catalysts and ultrathin films
Open access status:An open access version is available from UCL Discovery
Language:English
UCL classification:UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Chemistry

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