Proton exchange membrane
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robot Adding: [[it:Membrana a scambio protonico]]
{{Unreferenced|date=February 2007}}
A '''proton exchange membrane''' (PEM) is a [[semipermeable membrane]] generally made from [[ionomer]]s and designed to [[proton conductor|conduct protons]] while being impermeable to gases such as [[oxygen]] or [[hydrogen]]. This is their essential function when incorporated into a [[proton exchange membrane fuel cell]]: separation of reactants and transport of protons. PEMs can be made from either pure [[polymer]] membranes or from [[Composite material|composite]] membranes where other materials are embedded in a polymer matrix. One of the most common and commercially available PEM materials is [[Nafion]] which is made by [[DuPont]]. While nafion is an ionomer with a perfluorinated backbone like [[Teflon]], there are many other structural motifs used to make ionomers for proton exchange membranes. Many use polyaromatic polymers while others use partially fluorinated polymers.
Proton exchange membranes are primarily characterized by proton [[conductivity]] (σ), [[methanol]] permeability (P), and thermal stability.
==See also==
*[[Artificial membrane]]
*[[Semipermeable membrane]]
*[[Proton exchange membrane fuel cell]]
*[[Membrane electrode assembly]]
{{chem-stub}}
[[Category:Fuel cells]]
[[Category:Electrochemistry]]
[[Category:Polymers]]
[[Category:Hydrogen technologies]]
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[[it:Membrana a scambio protonico]]