Membrane Degradation Model for 3D CFD Analysis of Fuel Cell Performance as a Function of Time

The paper describes a development of a degradation model, which enables to predict time-dependent changes in performance of a polymer electrolyte fuel cell. The developed model consists of two main parts: 1) a new semi-empirical model taking into account changes in physico-chemical properties of a polymer electrolyte membrane operating in the fuel cell, 2) a validated CFD model computing the 3D performance of the cell. In the semi-empirical model, the degradation rates of the membrane thickness and conductivity depend on the
oxygen crossover rate. The acid group concentration is calculated from the membrane conductivity based on the percolation theory approach. The gas diffusion coefficients are modelled empirically as a function of the membrane thickness. The model of the membrane degradation is coupled with the CFD model and applied to analyse the cell behaviour as a function of time. The simulation shows that the cell current density decreases faster with lowering relative humidity and increasing temperature. The in-plane degradation of the membrane is non-uniform and depends on the local operating condition.