McColl, Kit; (2019) A Computational and Structural Study of Chloride Oxidation Compounds and Other Energy Materials. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Meeting complex and growing global energy demands requires the development of new materials with specifically tailored properties, made from earth abundant elements. A full understanding the chemical properties of a material required knowledge of its atomic level composition, crystal and electronic structure, which can be challenging or impossible to resolve using conventional experimental techniques alone. This thesis describes the analysis of synchrotron X-ray structural data, and the application of computational modelling using classical and quantum mechanical techniques to provide atomic level insights into two classes of energy materials. The first part of the thesis discusses electrocatalysts for solar-driven brine splitting to generate Cl2 and H2. The materials are based on the rutile crystal structure, and are studied computationally and with Extended X-ray Absorption Fine Structure and Pair Distribution Function analysis. These methods are applied in tandem to investigate the structure of highly active Ru(x)Ti(1-x)O2 and Ru(x)Sn(1-x)O2 nanoparticles made during the project. The materials comprise small particles of RuO2-rich Ru(x)(Ti, Sn)(1-x)O2 solid-solutions, dispersed on the surface of larger TiO2/SnO2 particles. This atomic level mixing in the solid-solution phase is thought to be key to their high catalytic activity and excellent selectivity towards chlorine evolution. In the second part of the thesis, I investigate two high energy density Mg battery cathode materials, namely V2O5 and anatase TiO2, using computational modelling. The studies provide an improved understanding of the defect and intercalation chemistry of these materials with a focus on achieving good Mg mobility, which is not generally observed in oxide cathodes but is critical for practical applications. Dopants are shown to modify Mg mobility in V2O5, and frustrated coordination is identified as the key to provide high Mg mobility in anatase. For both battery cathode systems, clear directions are indicated for experimental synthesis of improved materials.

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