UBC Theses and Dissertations
Fabrication and characterisation of Pt-Co electrocatalysts for oxygen reduction reaction in polymer electrolyte membrane fuel cells Pharkya, Pallavi
Electrocatalysts have tremendous impact on the performance of fuel cells as both cathodic and anodic reactions take place on the surfaces of the electrocatalysts. This work focuses on fabrication and characterization of novel Pt-Co electrocatalysts for oxygen reduction reaction in polymer electrolyte membrane fuel cells. High-energy ball milling was used for the fabrication of electrocatalysts. Alloy systems with varied ball to powder ratio, milling time and amount of process control agent were fabricated to optimize ball-milling conditions. Process control agents used were carbon and stearic acid. Ball to powder ratios of 39:1 or 78:1 were used and milling time was varied from 10 minutes to 90 hours. The optimized ball-milling conditions were then used to fabricate PtCo and PtCo/C alloy electrocatalysts. The low surface area of the ball-milled catalysts was further improved by lixiviation process. Microstructural characterization techniques, TEM and SEM, were used for the particle size determination and particle morphology, EDS was used to determine the bulk elemental composition of the electrocatalysts, XPS was performed to determine the oxidation state, surface elemental analysis and presence of oxidized species of the electrocatalysts. Electrochemical methods, namely, cyclic and potentiodynamic polarization were performed to obtain kinetic parameters, such as, exchange current density and Tafel slopes. These electrochemical kinetic parameters determine electrocatalytic activity of the catalysts. Performances of the fabricated electrocatalysts in this work were compared with commercial electrocatalysts from E-TEK.
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