Structural Optimization Using MHM

The MHM was exploited in optimization studies of CCL composition and thickness, using the relations specified in the section Effective Catalyst Layer Properties 

FIGURE 4.6 (a) Effect of the Nafion weight fraction, 7 /, in CCL with uniform composition on the fuel cell voltage, Eceih evaluated at different values of the current density, yo. Experimental data taken from Passalacqua et al. (2001) (crosses) are shown for comparison. (b) Comparison of polarization curves, calculated in the model of composition-dependent performance, with experimental data of Uchida et al. (1995a,b). 

As discussed in the section Ionomer Structure in Catalyst Layers Redefined in Chapter 3, a theory of composition-dependent effective properties that incorporates recent insights into stmcture formation in CCLs is yet to be developed. At present, the relations presented in the section Effective Catalyst Layer Properties from Percolation Theory in Chapter 3 do not account for agglomerate formation and skin-type morphology of the ionomer film at the agglomerate surface. Qualitative trends predicted by the simple structure-based catalyst layer theory should be correct, as confirmed by the results discussed in this section. 

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