We assume that these agglomerates exhibit homogeneity and are uniformly distributed within the catalyst bed, creating new macro-porosity between each agglomerate. Furthermore, we hypothesize that when electrolyte reaches the Nafion  -filled agglomerate, it is adsorbed by Nafion  , causing it to swell till it reaches saturation of 0.78. Structural characterisation of the agglomerate catalyst layer is described in Section 2.3.