Platinum electrocatalysts are important for a number of low and zero-emission energy technologies, including low temperature fuel cells. For reactions such as oxygen reduction at a fuel cell cathode, poor kinetics and harsh operating conditions (which lead to catalyst degradation) dictate the use of large volumes of Pt for efficient electrocatalysis. This need for a large quantity of Pt increases the cost of the fuel cell and makes the technology too expensive to compete with petroleum based energy alternatives typically used in automotive applications. Improving the effective utilization of Pt enables the same performance to be achieved with a smaller mass of Pt. A more effective use of Pt can be achieved through the use of alternative catalyst layer designs. The work presented in this thesis demonstrates three novel Pt catalyst layer designs with the aim of improving the effective utilization of Pt for electrocatalysis. These designs include pure Pt ordered porous electrodes (Pt-OP electrodes), supported Pt nanoparticle ordered porous electrodes (support@PtNP-OP electrodes) and nanobowl supported Pt NPs (support@PtNP nanobowls). These designs aim to enhance Pt utilization by improving: i) mass transport through the use of an open porous design; ii) Pt electrochemical stability via the use of stable materials throughout the electrocatalyst design and/or through support interactions; and iii) Pt catalytic activity via favorable interactions with support materials. The preparation of these new Pt electrocatalyst designs is presented through the use of sacrificial templates. The new materials were extensively characterized by electron microscopy, X-ray spectroscopy, and electrochemical methods. The alternative electrocatalyst designs demonstrated here provide new routes towards enhancing the utilization of Pt for electrocatalytic applications.
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Thesis advisor: Gates, Byron
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