# The effect of Nafion film on the cathode catalyst layer performance in a low-Pt PEM fuel cell

## TL;DR

This paper develops a single-pore model to analyze how Nafion film thickness affects oxygen transport and limiting current density in low-Pt PEM fuel cell cathode catalyst layers, explaining performance drops.

## Contribution

It introduces an analytical model that links Nafion film properties to cathode layer performance, highlighting the impact of film thickness on limiting current density.

## Key findings

- Limiting current density linearly depends on catalyst layer thickness.
- Thinner Nafion films reduce oxygen transport, lowering performance.
- Model explains observed performance issues in low-Pt catalyst layers.

## Abstract

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.