Nonlinear Water Transport Through a Polymer Electrolyte Membrane Under Transient Operation of a Proton Exchange Membrane Fuel Cell

A polymer electrolyte membrane is a core component of proton exchange membrane fuel cell. Since the ionic conductivity of polymer electrolyte membrane depends on water content, it is necessary to understand the water transport mechanism in the polymer electrolyte membrane. When the electric current demand is varied rapidly, the transient water transport results in the shortage or flooding in the polymer electrolyte membrane. The transient behavior of water transport in the polymer electrolyte membrane is nonlinear due to the water sorption/desorption mechanism. In this study, the nonlinear water transport mechanism of polymer electrolyte membrane is established to understand the transient behavior of water transport over the rapid change of electric current. Since the nonlinear dynamics delay the response of water transport under rapid change of electric current, system-level simulation is conducted to evaluate the system response by delayed water transport. Results show that the rapid change of electric current dramatically affects the water transport dynamics. As a result, this study confirms that water transport in the electrode is delayed depending on the polymer electrolyte membrane (PEM) thickness and that flooding occurs in the cathode depending on the relative humidity at the anode inlet.