Preparation of catalyst coated membranes using screen printing
Master Thesis
2013
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University of Cape Town
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Of the various types of fuel cells, Polymer Electrolyte Fuel Cells (PEFCs) have already been demonstrated in transportation appliances from light-duty vehicles to buses and in portable appliances including laptops and cell phones. A key component of a PEFC is its platinum electrocatalyst. With an estimated 75% of the world’s platinum reserves and resources in South Africa, local development of this technology will allow South Africa to become a major player in the growing hydrogen economy. This project therefore forms part of the Department of Science and Technologies strategy, to develop fuel cell technology in South Africa. More specifically, this study aims to contribute to the development of membrane electrode assembly (MEA) platform technology at the HySA/Catalysis Centre. In order to achieve this goal, a catalyst coated membrane (CCM) fabrication procedure was implemented using a newly acquired screen printer. In this procedure, catalyst ink is forced through a mesh onto a substrate, where it can then be transferred to a membrane via decal transfer to form a CCM. Two gas diffusions layers can then be placed on either side of the CCM forming a 5-layered MEA. Characterisation techniques of the catalyst ink, CCM and 5-layered MEA were successfully implemented such that future researchers can expand on the ideas. Catalyst inks with varying amounts of isopropanol, 1,2-propanediol and water were screened for their suitability for screen printing. In particular the catalyst ink rheology required for a smooth and even printed surface was determined for a given screen and squeegee combination. With all the established steps in pace, screen printing proved to be a fast and reliable approach for CCM fabrication with potential for future scale up and commercialisation. The fabricated CCMs performed on a par with a commercial Ion Power CCM, but under performed in comparison to a commercial Johnson Matthey (JM) MEA. Possible reasons for this include improved materials in the JM MEA and cell conditions favouring the JM MEA. Future projects which specifically arise from this work entail an investigation into the water management of the fuel cell environment at HySA/Catalysis, as well as a modification of the various steps in order to optimise the process and in doing so manufacture commercially viable MEAs.
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Hill, M. 2013. Preparation of catalyst coated membranes using screen printing. University of Cape Town.