Study of MEA Degradation in Operating PEM Fuel Cells

摘要

The durability of MEAs based on Nation membranes has been studied during on/off cycling operation.Two types of cycling test procedures differing in operating conditions have been defined.The difference between the two hydration states of the membrane differs from one set of tests to the other.The first goal was to show the influence of the mechanical stress induced by the successive hydrations and dehydrations on MEA lifetime.The effects of temperature,oxidizer humidification,and membrane thickness on the durability have also been investigated under the cycling test conditions the more representative of the automotive application.In parallel,the amounts of sulfate and fluoride ions contained in the water recovered from the fuel and oxidizer outlets have been measured.The presence of these anions is a proof of the chemical degradation of the ionomer.The mechanical (strain/stress curves) and permeation properties of the membranes have been analyzed before and after operation in order to quantify their degradation.Finally,an ex-situ ageing procedure has been developed to reproduce the cyclic hydration encountered by the membrane during these fuel cell tests.