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A proton exchange membrane or polymer electrolyte membrane (PEM) is a semipermeable membrane
Semipermeable membrane

A semipermeable membrane, also termed a selectively-permeable membrane, a partially-permeable membrane or a differentially-permeable membrane, is a membrane that will allow certain molecules or ions to pass through it by diffusion and occasionally specialized "facilitated diffusion." The rate of passage depends on the press...
 generally made from ionomer
Ionomer

An ionomer is a polymer that comprises repeat units of both electric charge neutral repeating units and a fraction of ionized units . Ionomers have unique physical properties including electrical conductivity and isoviscosity -- increase in ionomer solution viscosity with increasing temperatures.....
s and designed to conduct protons
Proton conductor

A proton conductor is an electrolyte, typically a solid electrolyte, in which movable hydrogen ions are the primary charge carriers....
 while being impermeable to gases such as oxygen
Oxygen

Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
 or hydrogen
Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the chemical symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly combustion and explosive Diatomic molecule gas with the molecular formula H2....
. This is their essential function when incorporated into a membrane electrode assembly
Membrane electrode assembly

A membrane electrode assembly is an assembled stack of proton exchange membranes , catalyst and electrode used in a fuel cell. The PEM is sandwiched between two electrodes which have the catalyst embedded in them....
 (MEA) of a proton exchange membrane fuel cell
Proton exchange membrane fuel cell

Proton exchange membrane fuel cells, also known as polymer electrolyte membrane fuel cells , are a type of fuel cell being developed for transport applications as well as for stationary fuel cell applications and portable fuel cell applications....
: separation of reactants and transport of protons.

can be made from either pure polymer
Polymer

A polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a variety of properties....
 membranes or from composite
Composite material

Composite materials are engineered materials made from two or more constituent materials with significantly different physical or chemical properties which remain separate and distinct on a macroscopic level within the finished structure....
 membranes where other materials are embedded in a polymer matrix.






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A proton exchange membrane or polymer electrolyte membrane (PEM) is a semipermeable membrane
Semipermeable membrane

A semipermeable membrane, also termed a selectively-permeable membrane, a partially-permeable membrane or a differentially-permeable membrane, is a membrane that will allow certain molecules or ions to pass through it by diffusion and occasionally specialized "facilitated diffusion." The rate of passage depends on the press...
 generally made from ionomer
Ionomer

An ionomer is a polymer that comprises repeat units of both electric charge neutral repeating units and a fraction of ionized units . Ionomers have unique physical properties including electrical conductivity and isoviscosity -- increase in ionomer solution viscosity with increasing temperatures.....
s and designed to conduct protons
Proton conductor

A proton conductor is an electrolyte, typically a solid electrolyte, in which movable hydrogen ions are the primary charge carriers....
 while being impermeable to gases such as oxygen
Oxygen

Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
 or hydrogen
Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the chemical symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly combustion and explosive Diatomic molecule gas with the molecular formula H2....
. This is their essential function when incorporated into a membrane electrode assembly
Membrane electrode assembly

A membrane electrode assembly is an assembled stack of proton exchange membranes , catalyst and electrode used in a fuel cell. The PEM is sandwiched between two electrodes which have the catalyst embedded in them....
 (MEA) of a proton exchange membrane fuel cell
Proton exchange membrane fuel cell

Proton exchange membrane fuel cells, also known as polymer electrolyte membrane fuel cells , are a type of fuel cell being developed for transport applications as well as for stationary fuel cell applications and portable fuel cell applications....
: separation of reactants and transport of protons.

Section

PEMs can be made from either pure polymer
Polymer

A polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a variety of properties....
 membranes or from composite
Composite material

Composite materials are engineered materials made from two or more constituent materials with significantly different physical or chemical properties which remain separate and distinct on a macroscopic level within the finished structure....
 membranes where other materials are embedded in a polymer matrix. One of the most common and commercially available PEM materials is Nafion
Nafion

Nafion is a sulfonated tetrafluoroethylene based fluoropolymer-copolymer discovered in the late 1960s by Walther Grot of DuPont. It is the first of a class of synthetic polymers with ionic properties which are called ionomers....
, a DuPont
DuPont

E. I. du Pont de Nemours and Company is an United States chemical industry that was founded in July 1802 as a gunpowder mill by Eleuth?re Ir?n?e du Pont....
 product. 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
Conductivity

Conductivity may refer to:*Electrical conductivity, a measure of a material's ability to conduct an electric current*Hydraulic conductivity, a property of a porous material's ability to transmit water...
 (s), methanol
Methanol

Methanol, also known as methyl alcohol, carbinol, wood alcohol, wood naphtha or wood spirits, is a chemical compound with chemical formula carbonhydrogen3oxygenhydrogen ....
 permeability (P), and thermal stability.

See also

  • Artificial membrane
    Artificial membrane

    Artificial membrane also known as synthetic membrane is a syntheticly created membrane which is usually intended for separation purposes in laboratory or in industry....
  • Dry electrolyte
  • Dynamic mechanical analysis
    Dynamic mechanical analysis

    Dynamic Mechanical Analysis , dynamic mechanical thermal analysis or dynamic thermomechanical analysis is a technique used to study and characterize materials....
  • Electroosmotic pump
    Electroosmotic pump

    An electroosmotic pump , or EO pump, is used for removing liquid flooding water from channels and gas diffusion layers and direct hydration of the proton exchange membrane in the membrane electrode assembly of the proton exchange membrane fuel cells....
  • Roll-to-roll


External links

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