Electrocatalyst development and modeling of nonisothermal two-phase flow for PEM fuel cells

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2011
Fıçıcılar, Berker
A macro-homogeneous, nonisothermal, two-phase, and steady state mathematical model is developed to investigate water and thermal management in polymer electrolyte membrane (PEM) fuel cells. An original two-phase energy balance approach is used to catch the thermal transport phenomena in cases when there is a signi cant temperature di erence between the fuel cell temperature and the reactants inlet temperatures like during cold start-up. Model considers in depth electrode kinetics for both anode and cathode reactions. External and internal mass transfer resistances on fuel cell performance are accounted by means of a thin-film and agglomerate approach. Developed model accounts for all substantial transport phenomena including diffusion of multi-component gas mixtures in the porous media, electrochemical reactions in the catalytic regions, water and proton transport through the solid polymer electrolyte, transport of electrons within the solid matrix, heat transport in the gas and solid phases, phase change and transport of water through porous diffusion media and catalyst layers. In this study, it is truly shown how significant heat and water transport are to overall fuel cell performance. Model predictions are validated by comparison with experimental data, involving polarization curves, saturation and temperature gradients. For optimal electrode kinetics purposes, an alternative novel hollow core mesoporous shell (HCMS) carbon supported Pt and Pt-Pd electrocatalysts were synthesized by microwave irradiation. HCMS carbon spheres were produced by two different carbon precursors with the template replication of solid core mesoporous shell (SCMS) silica spheres. Compared to Pt/VX and ETEK electrocatalysts, HCMS carbon based Pt and Pt-Pd electrocatalysts showed promising cathode and anode electrodics performance in the fuel cell environment.