Characterization and transport modeling of atypical porous materials

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The polymer electrolyte membrane fuel cell is the only currently available technology capable of matching the capabilities of the automotive internal combustion engine for high power, long range and short refueling times. The work proposed in this project will investigate, in detail, the multiphase transport processes occurring in all components of the porous electrode simultaneously. This will involve both novel experimental techniques and advanced pore scale modeling. All previous efforts to study the complex interactions in the electrode have been based on volume average modeling approaches which (a) require numerous constitutive relationships describing the multiphase transport properties which are not known and are challenging to measure in these atypical materials and (b) are theoretically unsound representations of the transport processes due to the failure of the volume averaging assumption in finite size domains and the inapplicability of such models to capillarity driven processes. This project will develop an advanced pore network modeling framework capable of simulating all relevant transport processes simultaneously with pore scale resolution to ensure that the critical effects of discrete water configurations are considered. Pore network modeling requires significantly less experimentally determined transport parameters and in fact can be used to predict some experimentally inaccessible information. The main information required by this modeling approach is structural information such as porosity and capillary pressure curves. Novel approaches will be developed for obtaining this information for all constituent layers of the fuel cell electrode. The result of this study will be a long awaited and much needed understanding of water transport mechanisms in the electrode and the the physical parameters of influence. The availability of this information will enable design of electrode structure and materials for optimum fuel cell performance through a comprehensive understanding of all related phenomena.