Enhanced performance and durability of shape-controlled octahedral PtNiX catalysts for advanced fuel cell applications
The rapid population growth and industrial development has intensified energy demand and climate issues, emphasizing the urgent need to shift from fossil fuels to more sustainable energy alternatives such as “green” hydrogen. Hydrogen fuel cell technologies are attractive as zero-emission solutions in transportation and other power sectors. However, the wider adoption of hydrogen fuel cells is bottlenecked by high costs associated with fuel cell stacks, more specifically of platinum group metal (PGM) catalysts, as well as insufficient performance and limited long-term durability. This thesis addresses the development, characterization, and performance evaluation of advanced octahedral Pt-based cathode ORR catalysts of proton exchange membrane fuel cells (PEMFCs), with a focus on better PGM utilization and enhanced catalyst durability. The work is structured of two primary aspects: i) optimization of catalyst synthesis, including a seed-mediated route for octahedral PtNi nanoparticles with high Pt loading, as well as rhodium and iridium doping to increase electrochemical surface area (ECSA), ORR activity, and stability; and ii) systematic evaluation of the key factors that influence the translation of high catalytic activity from liquid half-cell measurements to membrane electrode assembly (MEA) testing. Detailed studies on the morphology, structure, composition, and ORR performance and durability are conducted using techniques like rotating disk electrode (RDE), floating electrode technique (FET), and MEA. Advanced in situ and online methods were employed for time-resolved and potential-dependent analyses to further understand catalyst mechanisms. In summary, this thesis provides valuable insights into the design of robust and efficient fuel cell catalysts for practical applications.
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