Design, synthesis and characterization of the oxygen reduction reaction catalyst for polymer electrolyte membrane fuel cells

Zhang, Yanqi
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University of Delaware
The sluggish oxygen reduction reaction (ORR) kinetics remains the critical technical barrier to fuel cell technology commercialization. In this thesis, the mechanisms, critical problems, and current research activities are first discussed. Then, with insights gained from literature, two different types of catalysts are explored for the electrochemical reduction of oxygen. Pt/Sc2O3 was synthesized using wet chemistry approach. Analysis under highresolution transmission electron microscopy (HRTEM) revealed the unique nanosheet structure of the Sc2O3. Physical and chemical properties of the catalyst were examined including the morphology, particle size, and chemical bonding strength. Rotating disk electrode (RDE) measurement was carried out to evaluate the activity of the catalyst in an acidic environment. The observed catalyst activity is three times higher than the benchmark Pt/C. Furthermore, durability tests showed the electrochemical surface area (ECSA) losses of the catalyst is only one third of that of Pt/C after 30,000-cycles of durability test. The second catalyst explored iss designed for hydroxide exchange membrane fuel cells. Specifically, a platinum-free nano-Au supported on C was also produced under mild synthesis conditions. Ozone treatment was used to remove the surfactant on the surface of the particle. The activity was determined via RDE in alkaline medium. The specific activity of Au/C is remarkably approaching that of the Pt/C. In addition, the Au/C loses 9 % of the initial surface while the Pt/C has a loss of 40 % after a modified stressful durability test. The results from this study provide useful information and guidance to the research of future catalysts.