Ultrathin planar catalyst layers

The length scale i a 50 — 100 nm determines the effectiveness of catalyst utilization for spherical agglomerates. Analogous relations apply for ultrathin planar catalyst layers with similar thickness, L 100 — 200 nm. We consider layers that consist of Pt, water-filled pores and potentially an electronically conducting substrate. With these assumptions, we can put/(dfptc, XfXptc = 1 and g Sr) = 1. The volumetric exchange current density is, thus. 

Spherical and planar model geometries of agglomerates will be considered. The planar geometry leads to important conclusions about the performance of ultrathin catalyst layers. 

The alternative is to fabricate CCLs as ultrathin two-phase composites 100 mn -200 mn), in which electroactive Pt could form the electronically conducting phase, or Pt nanoparticles could be supported on a conductive substrate. The remaining volume should be filled with liquid water, as the sole medium for proton and reactant transport. The ultra-thin two-phase catalyst layer was explored by using the Poisson-Nemst-Planck (PNP) equations as employed for water-filled spherical agglomerates [69, 118]. The equations in Section 8.5.2 can be rewritten for the ID planar situation... 

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