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Abstract: This work presents a study of multi-phase flow through the cathode side of a polymer electrolyte membrane fuel cell employing an interdigitated flow field plate. A previously published model has been extended in order to account for phase change kinetics, and a comparison between the interdigitated flow field design and a conventional straight channel design has been conducted. It is found that the parasitic pressure drop in the interdigitated design is in the range of a few thousand Pa and could be reduced to a few hundred Pa by choosing diffusion media with high in-plane permeability. The additional compressor work due to the increased pressure loss will only slightly increase, and this may be offset by operating at lower stoichiometries as the interdigitated design is less mass transfer controlled, which means that the overall efficiency of the interdigitated arrangement will be higher. In the interdigitated design more product water is carried out of the cell in the vapor phase compared to the straight channel design which indicates that liquid water management might be less problematic. This effect also leads to the finding that in the interdigitated design more waste heat is carried out of the cell in the form of latent heat which reduces the load on the coolant. Finally we see that the micro-porous layer might help keep the gas diffusion layer substrate dry due to a potentially higher evaporation rate caused by a combination of the Kelvin effect and a larger specific surface area compared to the diffusion layer substrate. [Copyright &y& Elsevier]

A three-dimensional multiphase mode! that describes the liquid water flux through the porous media and into the gas flow channel of a proton exchange membrane fuel cell (PEMFC) cathode is presented. The mode! is based on the multifluid approach, thus solving one complete set of transport equations for each phase. It is used to investigate the effect of different material parameters on the predicted liquid water saturation in various layers, i.e., catalyst layer (CL), microporous layer (MPL), and gas diffusion layer (GDL). Each layer can be characterized by its porosity, permeability, and contact angle, while the Leverett function was used to describe the capillary pressure vs saturation. The irreducible saturation can be specified for each layer independent!y. An expression for the channel/GDL interface condition was developed, which accounts for the number of drop!ets per unit area at the GDL interface. Describing the different porous media by Leverett equations leads to a jump condition in saturation across each interface. In accordance with previous studies it is found that the MPL remains at a low saturation level, while the CL might become flooded depending on the fraction of hydrophilic pores. Under-the-land compression leads to an increased level of flooding compared to the channel section. [ABSTRACT FROM AUTHOR]

• A method for measurement of PEM fuel cell cathode electron and proton conductivity is developed. • The method is based on fitting of recent impedance model to the spectra measured in N2/H2 regime of cell operation. • The method is demonstrated using Fe-N-C-based PEM fuel cells. • The electron and proton conductivity of Fe-N-C cathodes are close to these parameters of Pt/C cathodes. • The method could be used for in-situ control of carbon corrosion in long-term cell operation. Impedance spectra of a PEM fuel cell with three Fe-N-C cathodes have been measured under the H 2 /N 2 testing regime. The spectra have been fitted using a recently developed physics-based impedance model, which takes into account finite proton (σ p) and electron (σ e) conductivity of the oxygen-free cathode catalyst layer. Fitting allowed to extract numerical data for σ p , σ e , the double layer capacitance, and the inductance of cables used for measuring impedance spectra. The values of σ p and σ e are close to what previously found for standard Pt/C electrodes, which is found for the first time using PGM-free catalysts. The method enables simultaneous measurement of reference proton and electron conductivity of PEMFC cathode. [ABSTRACT FROM AUTHOR]

A new platinum group metal (PGM)-free proton exchange membrane fuel cell (PEMFC) cathode catalyst materials, synthesized using the VariPore™ method by Pajarito Powder, LLC, are characterized for their structure and activity. The physico-chemical analysis of the iron-nitrogen-carbon (Fe-N-C) electrocatalysts show mesoporous carbon material effectively doped with iron and nitrogen. The materials have an average pore size of 7–8 nm and high specific surface area. The Fe-N-C catalysts exhibit good oxygen reduction reaction (ORR) activity in 0.5 M H 2 SO 4 electrolyte with high half-wave potential and sustainable electrochemical stability over 10,000 repeated potential cycles with insignificant losses in their activities. As cathode catalysts in a PEMFC, the Fe-N-C materials deliver remarkably good fuel cell performance at low overpotential approaching that of the commercial Pt catalyst. The high ORR electrocatalytic activity of these Fe-N-C catalysts is credited to the synergy between nitrogen-moieties, specifically pyrrolic-N, pyridinic-N, and graphitic-N, and iron in addition to the high mesoporosity that facilitate an effective reaction path in boosting the electrocatalytic activity and stability. [Display omitted] • State-of-the-art commercial PGM-free catalysts for ORR were characterized and evaluated. • Was shown that active centres are atomically dispersed. • Performance of electrocatalysts was evaluated in industrially manufactured MEA form-factor. • The fuel cell performance is close to the state-of-the-art R&D PGM-free catalysts. [ABSTRACT FROM AUTHOR]