Hydrogen and Oxygen Permeability through PEFC Membrane and Membrane Electrode Assembly

A proton exchange membrane (PEM) is an important component of a polymer electrolyte fuel cell (PEFC) from the viewpoint of proton transport. Only protons are desired to be transported through a membrane, but the feed gases also permeate. The permeation of the feed gas through a membrane affects the PEFC performance. Temperature and relative humidity dependencies of the hydrogen and oxygen permeability through a perfluorosulfonic acid (PFSA) membrane were measured. By considering that a membrane consists of three layers, i.e. a bulk layer sandwiched between skin layers, the transport properties of each layer were separated. The bulk layer effective diffusion coefficients of hydrogen and oxygen through both a PEM and an MEA were formulated as a function of temperature and RH. The oxygen transfer coefficient in the skin layer increased with RH, whereas the hydrogen transfer coefficient was almost constant regardless of RH.