1-D Computational Model of a PEM Fuel Cell Using Reaction Rate Law Kinetics to Model the Consumption of Hydrogen at the Anode

Abstract

Computational models of Polymer Electrolyte Membrane (PEM) fuel cell have historically simulated the anode side reaction assuming the system is mass transfer limited. Specifically, the models assume that the hydrogen gas mass transfer rate is much slower than the reaction rate. Although this assumption makes computational simulations easier, the model does not accurately describe the system. This model introduces a novel method of simulating the anode side reaction. Specifically, the model uses the reaction rate law kinetics of hydrogen gas adsorption onto the platinum electrode and the subsequent ionization of the hydrogen atom to model the anode side reaction dynamics. The benefit is that the model is capable of predicting the actual behavior of the system at the electrode and polymer membrane interface. Because of the computational complexity of this system, the model assumes that a fraction of the hydrogen gas in contact with the polymer membrane dissolves into the polymer membrane and diffuses to the cathode side. The fraction of hydrogen, which is dissolved into the polymer membrane, is proportional to the Damko¨hler number (Da). Specifically, the model assumes that if the reactant is not completely consumed when it comes into contact with the polymer membrane that some fraction of the hydrogen gas will dissolve into the polymer membrane and will be diffused to the cathode side. In addition, because of the slight negative charge of the polymer membrane, the model assumes that no oxygen diffuses into the polymer membrane.