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Title: Catalysts for oxygen evolution
Author: Davies, H. L.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1991
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The efficiency of photochemical systems for water cleavage into hydrogen and oxygen depends on the discovery of suitable catalysts for the reduction and oxidation reactions. The most widely studied oxygen catalytic material has been ruthenium dioxide hydrate; however, its activity depends on its degree of hydration. Highly hydrated ruthenium dioxide (RuO2.xH2O) is a poor O2 catalyst and readily corrodes to RuO4 in the presence of a strong oxidant. Few kinetic studies have been carried out on the dissolution of powder suspensions by various oxidants but RuO2.xH2O is an ideal subject for such a study since the corrosion reaction is relatively simple and can be followed spectrophotometrically. Chapter Three describes a model for the corrosion kinetics of a surface-controlled reaction for a powder dispersion whereby the particle size distribution follows the log-normal law. This was then tested on previously published kinetic data on the dissolution of a polydispersed powder suspension. In Chapter Four, a kinetic study of the dissolution of RuO2.xH2O by BrO3- ions as a function of [BrO3-], [RuO2.xH2O] and temperature is described. This showed that the kinetics obeyed the inverse cubic rate law, implying that the powder is monodispersed and the rate of dissolution is proportional to the surface area. The result of a kinetic study of the dissolution of RuO2.xH2O by CeIV ions is described in Chapter Five. The kinetics were studied as a function of [CeIV]:[RuO2.xH2O] ratio, [CeIII] and temperature. The results were interpreted using an electrochemical model in which the CeIV reduction and the RuO2.xH2O oxidation are assumed to be highly reversible and irreversible processes respectively, mediated by the dissolving RuO2.xH2O microelectrode particles. Chapters Six and Seven describe the results of a kinetic study of water oxidation by CeIV ions catalysed by Ru-Adams and RuO2 (anhydrous), respectively. The kinetics were studied as a function of [CeIII], [catalyst] and temperature and were interpreted using an eletrochemical model of redox catalysis where the catalyst particles are considered as microelectrodes which mediate electron transfer between a Nernstian reaction (reduction of CeIV) and an irreversible reaction (oxidation of water).
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available