A single--pore model for performance of the cathode catalyst layer (CCL) in a PEM fuel cell is developed. The model takes into account oxygen transport though the CCL depth and through the thin Nafion film, separating the pore from Pt/C species. Analytical solution to model equations reveals the limiting current density $j_N^{ \rm lim}$ due to oxygen transport through the Nafion film. Further, $j_N^{ \rm lim}$ linearly depends of the CCL thickness, i.e., the thinner the CCL, the lower $j_N^{ \rm lim}$. This result may explain unexpected lowering of low--Pt loaded catalyst layers performance, which has been widely discussing in literature.
Categories: physics.chem-ph