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Title: Sol-gel processing of ruthenium and iridium dioxides
Author: Osman, Julian Robert
Awarding Body: University of St Andrews
Current Institution: University of St Andrews
Date of Award: 1998
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The synthesis of the Ru4O64+(aq) ion and attempts to produce derivative complexes of it are explored. Although crystals suitable for examination by single crystal X-Ray crystallography were not obtained, the core structure of the Ru4Os4+ ion in solution has been successfully determined using Ru K edge EXAFS spectroscopy. The refined results for solutions of the ion in aqueous acid, provide strong indications that the ion has an adamantanoid core arrangement in solution and that core structures based on hydroxo groups i.e Ru4(OH)124+ can be ruled out. Preparation and controlled hydrolysis of a variety of ruthenium precursors aimed at preparing gels of RuO2.nH2O gave at best powders. For example, only RuO2 powders were obtained by raising the pH of solutions of the Ru4O64++ ion. However, gels of a RuO2-TiO2 mixed oxide were readily prepared from the alkoxides. From TGA/DTA, X-Ray, and electron microscopy data these proved to be a mixture of two different oxide phases rather than a solid solution, hi some samples the RuO2 phase contains some of the smallest RuO2 nanoparticles so far reported. The mixed oxide gels and powders obtained were found to contain a number of impurities. Work performed on the iridium aqua ion [Ir(H2O)6]3+ is reported along with experiments to produce mixed IrO2-TiO2 oxides using iridixun ethoxide and iridium acetate complexes as starting materials. The aqua ion was found to give a powder product but gels were obtained from the other two precursors. The gels have been characterized and it was found that IrO2 is highly dispersed within a TiO2 matrix. The electrocatalytic properties of the IrO2 containing gels have been determined by studying the rates of oxygen evolution and the rate of consumption of cerium (IV) ions. The results show that the sol-gel derived IrO2 systems show good activity towards catalysing oxygen evolution by these ions.
Supervisor: Crayston, Joe A. ; Richens, David T. Sponsor: Engineering and Physical Sciences Research Council (EPSRC) ; Johnson Matthey plc
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QD181.R9O8 ; Ruthenium