2. Membranes for PEMFC fuel cells

2.1 Physical and chemical properties of membranes

The performance of a membrane is linked to its proton conductivity, which in turn depends on temperature. In the case of ionomers with a strongly hydrophilic group, such as a sulfonate group, proton conductivity is also dependent on the membrane's water content. The more hydrated the membrane, the higher its proton conductivity. Several parameters can be determined to evaluate these notions of conductivity and hydration. Equivalent weight (EW), ion exchange capacity (IEC) and proton conductivity σ are measured to assess the membrane's ability to transport protons. Membrane hydration, meanwhile, is determined by water content λ, water retention W _retention and membrane swelling. For high-temperature...