Non-uniform agglomerate cathode catalyst layer model on the performance of PEMFC with consideration of water effect

Highlights

CL hydration is favorable at low current, but prohibits oxygen transfer at high current.

Non-uniform CL with higher porosity near GDL is preferred.

Non-uniform CL with higher electrolyte fraction in the agglomerate near M is preferred.

Smaller agglomerate size near M is preferred at ohmic limited regime.

Smaller agglomerate size near GDL is preferred at mass transfer limited regime.

Abstract

We focus on the effect of cathode catalyst layer physical structure on the cell performance of proton exchange membrane fuel cell (PEMFC). At low polarization, high inlet humidification predicts better cell performance because of the more active surface in the CL. As polarization is extended near the mass transfer limited regime, high humidification only renders a flooded electrode and inferior cell performance. Catalyst layer with better capillary water transport parameters performs better than that with inferior water repulsion capability. Permeation in the gas diffusion layer (GDL) is important for efficient oxygen diffusion in mass transfer influenced regime. On the other hand, the permeability in catalyst layer only has secondary effect.

The distribution of material properties in the CL is studied for the MEA fabrication strategy. The CL is divided into three sub-layers with changing material properties. With water effect considered, better performance is obtained for higher porosity near the GDL, higher electrolyte fraction in the agglomerate near the membrane. The effect of agglomerate particle size differs in the ohmic and mass transfer controlled regimes. Larger agglomerate size near GDL is preferred in the ohmic limited regime, while smaller size near GDL performs better if operated at mass transfer controlled regime.

Keywords

  • PEMFC;
  • MEA;
  • Non-uniform catalyst layer;
  • Agglomerate model;
  • Liquid saturation;
  • Water content

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