Investigating the performance and degradation of low Platinum loaded proton exchange membrane fuel cells

Official URL: https://risc01.sabanciuniv.edu/record=b3390562

Reduction of Platinum (Pt) loading in proton exchange membrane fuel cells (PEMFCs) without sacrificing performance and durability is essential for the commercial viability of these devices. Comprehending the impact of the catalyst layer (CL) design variables including Pt-loading, Pt/C weight ratio, ionomer loading, and dilution as well as the interaction of these variables, provides insights for increasing the performance and durability of low Pt-loaded PEMFCs. In this thesis, the impact of CL characteristics and operating conditions on the cell performance, oxygen transport resistances, ionic potential loss, and cathodic overpotential is first evaluated using a detailed pseudo-three-dimensional (P3D) model. The model employs a multiphase non-isothermal P3D approach coupled with a detailed electrochemical kinetic sub-model concerning the CL microstructural features as well as the mixed wettability pore size distribution mathematical sub-model accounting for microstructural characteristics of different porous layers. By further developing the P3D model into a transient one, the impact of the CL characteristics on the voltage under and overshoot is discussed. Based on the modeling results, systematic experiments are developed and executed to isolate the specific effects of CL thickness, Pt-loading, Pt/C ratio, and carbon support material. A range of comprehensive in-situ electrochemical characterization methods is employed to gain insights into the beginning-of-life (BOL) performance of the samples. Moreover, the durability of PEMFCs of different CL features is evaluated under two accelerated stress tests (ASTs) simulating the Pt-dissolution and carbon corrosion degradation mechanisms.