Flooded agglomerate model

The equations used in these models are primarily those described above. Mainly, the diffusion equation with reaction is used (e.g., eq 56). For the flooded-agglomerate models, diffusion across the electrolyte film is included, along with the use of equilibrium for the dissolved gas concentration in the electrolyte. These models were able to match the experimental findings such as the doubling of the Tafel slope due to mass-transport limitations. The equations are amenable to analytic solution mainly because of the assumption of first-order reaction with Tafel kinetics, which means that eq 13 and not eq 15 must be used for the kinetic expression. The different equations and limiting cases are described in the literature models as well as elsewhere. 

The membrane electrode assembly (MEA), which consists of three components (two gas diffusion electrodes with a proton exchange membrane in between), is the most important component of the PEMFC. The MEA exerts the largest influence on the performance of a fuel cell, and the properties of each of its parts in turn play significant roles in that performance. Although all the components in the MEA are important, the gas diffusion electrode attracts more attention because of its complexity and functions. In AC impedance spectra, the proton exchange membrane usually exhibits resistance characteristics the features of these spectra reflect the properties of the gas diffusion electrode. In order to better understand the behaviour of a gas diffusion electrode, we introduce the thin-film/flooded agglomerate model, which has been successfully applied by many researchers to... 

The characteristics of a gas diffusion electrode can also be illustrated by the thin-film/flooded agglomerate model. Paganin et al. [4] summarized the parameters that often appear in the impedance spectra of H2/02 and H2/air fuel cells ... 

Springer TE, Raistrick ID (1989) Electrical impedance of a pore wall for the flooded-agglomerate model of porous gas-dilFusion electrodes. J Electrochem Soc 136 1594-603... 

Pinnow S, Chavan N, Turek T (2011) Thin-film flooded agglomerate model for silver-based oxygen depolarized cathodes. J Appl Electrochem 41 1053-1064. doi 10.1007/sl0800-011-0311-2... 

To describe the function of these CLs in PEM fuel cells, in many works a flooded agglomerate model (FAM) is utilized (Baschuk and Li, 2000 Jaouen et al., 2002 Schwarz and Djilali, 2007). In recent years, FAM has been used as a sub-model in the CFD modelling of fuel cells (Schwarz and Djilali, 2007 Kamarajugadda and Mazumder, 2008). 

Both macrohomogeneous and flooded agglomerate models predict doubling of the Tafel slope in the proton- and oxygen-limiting regimes. Thus, polarization curves cannot be used to distinguish between these two models. The decisive experiment would be to measure the distribution of... 

Electrode Kinetic and Mass Transfer for Fuel Cell Reactions For the reaction occurring inside a porous three-dimensional catalyst layer, a thin-film flooded agglomerate model has been developed [149, 150] to describe the potential-current behavior as a function of reaction kinetics and reactant diffusion. For simplicity, if the kinetic parameters, such as flie exchange current density and diffusion limiting current density, can be defined as apparent parameters, the corresponding Butler-Volmer and mass diffusion relationships can be obtained [134]. For an H2/air (O2) fuel cell, considering bofli the electrode kinetic and the mass transfer, the i-rj relationships of the fuel cell electrode reactions within flie catalyst layer can be expressed as Equations 1.130 and 1.131, respectively, based on Equation 1.122. The i-rj relationship of the catalyzed cathode reaction wifliin the catalyst layer is... 

Similar agglomerate approaches were adopted by Iczkowski and Cutlip [30] and by Bjbmbom [31], Those works already identified the doubling of the apparent Tafel slope as a universal signature of the interplay of mass transport limitations and interfacial electrochemical kinetics. Flooded agglomerate models have been employed since then to analyze sources of irreversible voltage losses, optimum electrode thickness, and effectiveness of catalyst utilization. Moreover, it was... 

For both curves, fitting yields very close values of the exchange current density of k — 10 A cm (Table 5.5). This value of i is nearly two orders of magnitude less than the one obtained in Dobson et al. (2012) from the same set of curves using a flooded agglomerate model. Note that, as discussed in Dobson et al. (2012), their value is an order of magnitude higher than expected thus, the values of i indicated in Table 5.5 could be closer to reality. 

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