Catalyst layer performance modeling Cathode

Wang15 investigated heat and mass transport and electrochemical kinetics in the cathode catalyst layer during cold start, and identified the key parameters characterizing cold-start performance. He found that the spatial variation of temperature was small under low current density cold start, and thereby developed the lumped thermal model. A dimensionless parameter, defined as the ratio of the time constant of cell warm-up to that of ice... 

Recently Meng17 developed a transient, multiphase, multidimensional PEFC model to elucidate the fundamental physics of cold start. The results showed the importance of water vapor concentration in the gas channels, which implies that large gas flow rates benefit cold-start performance. They also found that ice growth in the cathode catalyst layer during cold start was faster under the land than under the gas channels, and accumulated more at the interface between the cathode catalyst layer and GDL. 

M. Eikerling and A. Komyshev, Modeling the performance of the cathode catalyst layer of polymer electrolyte fuel cells, J. Electroanal. Chem. 435 (1998) 98-106. 

Figure 8.15. Plot of cell potential vs. fuel cell current density, (/o), indicating the effect of liquid water accumulation in the CCL on performance (soUd hne). The interplay of liquid water accumulation in pores and impeded oxygen transport causes the transition from the ideally wetted state to the fully saturated state (dotted tines), as indicated [51]. (Reprinted from Electrochimica Acta, 53.13, Liu J, Eikerting M. Model of cathode catalyst layers for polymer electrolyte fuel cells The role of porous structure and water accumulation, 4435— 46, 2008, with permission from Elsevier.)...

The transport properties of water-filled nanopores inside of agglomerates and the properties of the ionomer film at the agglomerate surface define local reaction conditions at the mesoscopic scale. These local conditions, which involve distributions of electrolyte phase potential, proton density (or pH), and oxygen concentration, determine the kinetic regime, under which interfacial electrocatalytic processes must be considered. Combining this information, a local reaction current can be found, which represents the source term to be used in performance modeling of the cathode catalyst layer. 

Below, the model for DMFC cathode impedance is presented, assuming the electrochemical mechanism of MOR on the cathode side (Kulikovsky, 2012b). In this section, the nonstationary version of the DMFC cathode performance model (the section Cathode Catalyst Layer in a DMFC ) is used to calculate the cathode impedance. As discussed in the section Cathode Catalyst Layer in a DMFC, the model takes into account spatial distribution of the MOR and ORR, through the cathode thickness. It is shown below that the spatial separation of MOR and ORR, discussed in the section Cathode Catalyst Layer in a DMFC, leads to the formation of a separate semicircle in the impedance spectrum. 

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