The Impact of Wettability on Effective Properties of the Cathode Catalyst Layer in a Proton Exchange Membrane Fuel Cell

The produced liquid water in the cathode catalyst layer (CCL) has a signi cant effect on the operation of a proton exchange membrane fuel cell (PEMFC). To investigate this effect, the transport of oxygen in the CCL in the presence of immiscible liquid water is studied by applying a two-dimensional pore scale model. The CCL was reconstructed as an agglomerated system. To explore the wettability effects, different contact angles were considered at the surface of agglomerates. The effective diffusivity of oxygen was calculated under different contact angles at various saturation levels. The same effective diffusivity was obtained for hydrophilic and hydrophobic domains at lower saturations; however, at saturation above 0.4, the hydrophobic domain provided higher effective diffusivity values. The effect of water coverage at reaction surface areas was investigated. The results showed that, at a saturation of 0.4, the hydrophobic domain with the contact angle of 150 has about 2 times more available surface area due to a different distribution of the water phase compared to the hydrophilic domain with a contact angle of 20.

Keywords:

PEM fuel cell , Cathode catalyst layer , Two-phase  ow , Contact angle , Effective diffusivity