Multiscale Modeling of a Proton Exchange Membrane Fuel Cell: Macroscopic Fuel Cell Model and Experimental Validation

Nowadays, Proton-exchange membrane fuel cells (PEMFCs) show drawbacks associated with their high costs and sluggish kinetics, [1,2]. One of the most attractive alternatives for the improvement of the PEMFCs is the development of mathematical models. Those models allow to analyze the effects of variables such as temperature, pressure, humidity and flow of reactive gases on the operation of the fuel cell [3]. Therefore, the number of publications related with fuel cell models has increased in the past years and several models are available in the literature with different approximations, several kinds of transport approaches and kinetic models, also different detail levels and complexity [4].  However, most of those models still rely on a lot of empirical parameters and quantities, which in most cases do not have a physical meaning or are difficult to obtain.

For these reasons, considering the increase of computer capacity, analysis at different scales have been made in order to obtain a better understanding of the physicochemical phenomena involved in the operation of a fuel cell [5], specially the phenomena directly related with the catalytic layers, where the device has its main drawbacks. Also, methodologies to integrate results from different simulation scales are very attractive and they are an active area of study nowadays [5,6].

Considering these issues, a PEMFC multiscale model is presented in this research. This model integrates a kinetic model for the oxygen reduction reaction, an electric double layer description and a macroscopic transport model. The kinetic model consists of a reaction mechanism studied with density functional theory - DFT. The effects of the formation of water adlayers at the electric double layer of the cathode were studied by molecular dynamics. Finally, the transport through the gas diffusion layers and the membrane was described with a diffusion model based on the Stefan-Maxwell equation.

Results for output flows of reactive gases and water, and also current-voltage curves (i-V) are obtained for different operation conditions. They are discussed and compared with experimental data with the aim of support the applied multiscale methodology and to make a contribution to the area of modeling of the PEMFCs.

References:

[1]    Y. Wang, K.S. Chen, J. Mishler, S.C. Cho, X.C. Adroher, Appl. Energy 88 (2011) 981.

[2]    E. Antolini, E.R. Gonzalez, J. Power Sources 195 (2010) 3431.

[3]    A.Z. Weber, J. Newman, J. Electrochem. Soc. 150 (2003) A1008.

[4]    A.Z. Weber, J. Newman, Modeling Transport in Polymer-Electrolyte Fuel Cells., 2004.

[5]    K.-D. Kreuer, S.J. Paddison, E. Spohr, M. Schuster, Chem. Rev. 104 (2004) 4637.

[6]    R.F. de Morais, P. Sautet, D. Loffreda, A. a. Franco, Electrochim. Acta 56 (2011) 10842.