Multiscale Modeling of a Proton Exchange Membrane Fuel Cell: Effect of Electric Double Layer in Cathodic Interface at Different O2 Concentrations
Authors: Nuñez Toledo Laura Elisa , Castañeda Ramírez Sergio , Ribadeneira Paz Rafael 
Published: February 2020

Mathematical models have played an important role for the understanding of proton exchange membrane fuel cells (PEMFCs ) (1), (2), (3), (4). Specifically, multiscale models attempt to take into account the physicochemical phenomena from atomistic to macroscopic scales to reliably reproduce the PEMFCs performance and reducing the number of parameters involved in equations. Through the last years multiscale models have employed different approaches: from non equilibrium thermodynamics, electrodynamics, and transport equations in general (5), (6), (7), (8), (9), (10), (11) to statistical mechanics using kinetic monte carlo method (MC) (11), or quantum physics using density functional theory (DFT) (7), (11), (12).

In this work a molecular dynamics (MD) simulation of a platinum / oxygen / water interface is employed to describe the formation of the electric double layer (EDL) and also an electric overpotential associated with different operational concentrations of molecular oxygen. Those overpotentials are included in kinetic equations of the oxygen reduction reaction (ORR) mechanism for the cathode. Finally this ORR kinetics is included in a multiscale model of a PEMFC (13). Such multiscale model also utilizes other three approaches: DFT to calculate activation energies (14), a modified transport model for the membrane (15) and also it uses the transition state theory for the catalyst layer. It is expected that this EDL coupling will generate an improvement of the description capacity of the multiscale model in comparison with the experimental data of the electroosmotic drag coefficients vs current density for different relative humidities of the cathode.

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