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Title: Oxygen reduction on platinum
Author: Gara , Matthew
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2013
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Proton exchange membrane (PEM) fuel cells have the potential to provide a clean and convenient source of power for applications such as vehicle transport. At their heart lies a platinum catalyst which is used to reduce oxygen to water. Although platinum is expensive it is the best elemental catalyst for the reaction. In order to make better use of the platinum and reduce production costs, nanoparticulate platinum is dispersed onto a carbon support. This results in a greater surface area per gram of platinum used. Efforts to improve the performance of fuel cells and make them cost effective have so far revolved around increasing the surface area. However in doing this the inter-particle spacing and diffusional characteristics of the catalyst have been ignored. In order to address this oversight, this thesis takes a novel bottom up approach to better understanding the oxygen reduction reaction on nanoparticulate platinum, supported on carbon. By using a model system and simulating the diffusional environment, this work reveals new insights into the oxygen reduction reaction. In Chapter 1 the fundamental electrochemical principles which underpin the subsequent work shall are examined. Chapter 2 begins with a look at the history of fuel cell development, before assessing the modern PEM fuel cell and the challenges faced in the present day to make it ·a viable power source. In Chapter 3 carbon electrode materials are assessed with a view towards their use as a substrate for platinum ~atalysts. The results gained f:rom , ~~is prove useful in later chapters and are both novel and insightful for the selection of PEM fuel cell catalyst supports. In Chapters 4 and 5 voltammetry at nanomaterial modified electrodes are extensively analysed, using electrochemical simulation techniques. This reveals that diffusion can play a role in effects which are assumed to be purely kinetic. From this a major flaw is exposed in the currently accepted measures of oxygen reduction catalyst activity. Chapter 6 brings the information garnered from the previous chapters together. In this chapter nanoparticulate platinum dispersed onto a flat carbon substrate is used as a model system of a typical oxygen reduction catalyst. The resulting voltammetry from the model surfaces is then fitted effectively to results from electrochemical simulations, paying close attention to the diffusional environment around the nanoparticles. This approach leads to a key finding which had hitherto gone unrecognised.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available