Impact of non-uniform wettability in the condensation and condensation-liquid water intrusion regimes in the cathode gas diffusion layer of proton exchange membrane fuel cell

Abstract

The impact of variations in the wettability properties of the gas diffusion layer substrate on the liquid water distribution and the reactant gas access is studied from pore network simulations considering two main cases: a degradation case where the fraction of hydrophilic pores increases and a case where the spatial distribution of the hydrophobic agent is non-uniform with hydrophobic surfaces and a central region of mixed wettability. Contrary to previous works, this impact is assessed for various regimes of liquid water occurrence. The latter notably include the condensation regime and the mixed regime where the occurrence of liquid water in the gas diffusion layer results from both condensation under the rib and the ingress of liquid water from the catalyst layer or the microporous layer. The study shows that the wettability variation impact is highly dependent on the regime, i.e. on the operating conditions. Whereas this impact is minor when the conditions correspond to the occurrence of the pure condensation regime where the liquid water is confined in the region below the rib, it can be quite significant in the mixed regime when the conditions are such that liquid water is present also in the region below the channel.