PROTON EXCHANGE MEMBRANE FUEL CELL MODIFICATION FOR CATALYTIC COGENERATION OF HYDROGEN PEROXIDE AND ELECTRICITY
Date
2024
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Proton exchange membrane fuel cells are susceptible to airborne sulfur contaminants that cause catalyst degradation, disrupting the oxygen reduction reaction and producing hydrogen peroxide as an undesired intermediate product within the membrane electrode assembly. Sulfur adsorbs onto the surface of the platinum/carbon catalyst, blocking active platinum sites and changing the reaction mechanism from a 4e- pathway producing water, to a 2e- pathway producing hydrogen peroxide. Today, 95% of commercially available hydrogen peroxide is made from an expensive, energy-intensive, and environmentally harmful anthraquinone oxidation process. This thesis seeks to take advantage of the described fuel cell vulnerability and uses ex-situ rotating ring-disk electrode methodology to validate the concept for a modified catalyst for cogeneration of hydrogen peroxide and electricity. Mechanisms behind this electrochemical process could provide a scalable, environmentally friendly, and more cost-effective production method of hydrogen peroxide.In this work, a catalyst modification process is developed using sulfur adsorption on platinum and for the first time, the stability of the modified catalyst and peroxide production is tested over long periods of time and under potential control. Cyclic voltammetry confirmed the stability of the modified catalyst for a minimum of 24 hours. The activity after catalyst modification is measured under polarization (0 V 1V), as well as potentiostatic control at 0.1 V, 0.2 V, 0.3 V, and 0.4 V over time. The results reveal a possible preferred condition for the maximized production of H2O2 and electricity at an applied potential near 0.3 V. While existing studies rely on an indirect method of peroxide quantification, the production of peroxide is confirmed via a dual traditional-potentiometric titration in the bulk solution after long term stability testing of 24 hours. Experiments reveal a possible rearrangement of adsorbed sulfur or some other change to the surface previously unknown from short-term tests. The concept for the modified catalyst was validated in these ex-situ tests and should be repeated in-situ in a single cell proton exchange membrane fuel cell for scaled-up production.
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Electrical engineering, Chemical engineering, Materials Science, catalysis, electrochemistry, hydrogen peroxide, oxygen reduction reaction, PEM fuel cells
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74 pages
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