A Novel Model of Water Hydration in PEM Fuel Cell in Dynamic Operations

Polymer membrane (PEM) fuel cell requires good hydration in order to deliver high performance and ensure long life operation.  Water is essential for membrane proton conductivity which increases by nearly six orders of magnitude from dry to fully hydrated. Adequate water management in PEM fuel cell is crucial in order to avoid an imbalance between water production and water removal from the fuel cell.

In the present study, a novel mathematical zero-dimensional model has been formulated for the water mass balance and hydration of a polymer electrolyte membrane. This model incorporates all the essential fundamental physical and electrochemical processes occurring in the membrane electrolyte and considers the water adsorption/desorption phenomena in the membrane. The effect of diffusivity model, surface roughness and water content driving force is considered. The model is validated against available experimental data.

In the results it is shown that the fuel cell water balance calculated by this model display better fit with experimental data-points compared with model where only water transport equilibrium were considered. We conclude that this discrepancy is due a different rate of water transport when membrane absorption/ desorption is considered in the model. The model becomes useful when studying fuel cells in dynamic conditions.