Proton models, mesoscopic scale

Molecular modeling of PT at dense arrays of protogenic surface groups (SGs) demands ab initio quantum mechanical calculations. The starting point for the development of a viable model of surface proton conduction in PEM is the self-organized PEM morphology at the mesoscopic scale. Eigure 2.30a illustrates the random array of hydrated and ionized sidechains that are anchored to the surface of ionomer bundles. 

In the section Hierarchical Model of CCL Operation, a hierarchical modeling framework will be presented it couples multiple effects of proton and oxygen transport at the mesoscopic scale of agglomerates and at the macroscopic scale of the layer. In that general case, the CL effectiveness factor can be defined by... 

The transport properties of water-filled nanopores inside of agglomerates and the properties of the ionomer film at the agglomerate surface define local reaction conditions at the mesoscopic scale. These local conditions, which involve distributions of electrolyte phase potential, proton density (or pH), and oxygen concentration, determine the kinetic regime, under which interfacial electrocatalytic processes must be considered. Combining this information, a local reaction current can be found, which represents the source term to be used in performance modeling of the cathode catalyst layer. 

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