Ionomer in catalyst layer

Ionomer in Catalyst Layers Structure Formation and Performance... 

Cold start Product water absorbed in ionomer in catalyst layer, taken away as vapor in gas flow, and frozen into ice in catalyst layer pores Results increasing membrane thickness increases water capacity but decreases water absorption process, increasing ionomer volume fraction increases ionomer water capacity and enhances membrane water absorption cell start-up is better under potentiostatic condition than galvanostatic condition Jiao and Li, 2010... 

A viable approach to optimize the dispersion and structure of ionomer in catalyst layers is, thus, to make the surface of PPG agglomerates sufficiently hydrophilic, as to achieve the favorable orientation of the ionomer film, depicted on the left-hand side of Figure 3.41. Essentially, in this configuration, water exists where it is needed, at the interface with Pt. The ionomer structure is optimally utilized to provide high proton concentration in the interfacial water film. At the same time, the secondary pore space remains hydrophobic and thus water-free. 

The structural picture of ionomer in catalyst layers, unraveled in this section, suggests that extrapolation of bulk membrane properties in terms of water uptake, water binding, and proton transport skews specific properties of ionomer in CLs and is not generally feasible for the purpose of CL modeling. One needs to adapt mechanisms of water and proton transport to the thin-film ionomer morphology, where (i) proton transport is dominated by surface properties of ionomer and (ii) electrocatalytic properties are determined by the interfacial thin-film structure formed by Pt/C surface, ionomer film, and a thin intermediate water layer. 

Xei Volume fraction of ionomer in catalyst layer (dimensionless)... 

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See also in sourсe #XX -- [ , , , , , , , , , , , , , , , ]

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