A proton conductor is an electrolyte, typically a solid electrolyte, in which H⁺ are the primary charge carriers.

Composition

Acid solutions exhibit proton-conductivity, while pure proton conductors are usually dry solids. Typical materials are polymers or ceramic. Typically, the pores in practical materials are small such that protons dominate

direct current Direct current (DC) is one-directional flow of electric charge. An electrochemical cell is a prime example of DC power. Direct current may flow through a conductor such as a wire, but can also flow through semiconductors, insulators, or eve ...

and transport of cations or bulk solvent is prevented.

Water ice Water ice could refer to: * Ice formed by water (as opposed to other substances) *The alternate term for various similar frozen fruit-flavoured desserts: ** Italian ice primarily in Philadelphia and the Delaware Valley **Sorbet Sorbet (), also ...

is a common example of a pure proton conductor, albeit a relatively poor one. A special form of water ice,

superionic water Superionic water, also called superionic ice or ice XVIII is a phase of water that exists at extremely high temperatures and pressures. In superionic water, water molecules break apart and the oxygen ions crystallize into an evenly spaced lat ...

, has been shown to conduct much more efficiently than normal water ice. Solid-phase proton conduction was first suggested by Alfred Rene Jean Paul Ubbelohde and S. E. Rogers. in 1950, although electrolyte proton currents have been recognized since 1806. Proton conduction has also been observed in the new type of proton conductors for fuel cells – protic organic ionic

plastic crystal A plastic crystal is a crystal composed of weakly interacting molecules that possess some orientational or conformational degree of freedom. The name plastic crystal refers to the mechanical softness of such phases: they resemble waxes and are easil ...

s (POIPCs), such as 1,2,4-triazolium perfluorobutanesulfonate and

imidazolium Imidazole (ImH) is an organic compound with the formula C3N2H4. It is a white or colourless solid that is soluble in water, producing a mildly alkaline solution. In chemistry, it is an aromatic heterocycle, classified as a diazole, and has non-a ...

methanesulfonate. In particular, a high ionic conductivity of 10 mS/cm is reached at 185 °C in the plastic phase of imidazolium methanesulfonate. When in the form of thin membranes, proton conductors are an essential part of small, inexpensive fuel cells. The polymer

nafion Nafion is a brand name for a sulfonated tetrafluoroethylene based fluoropolymer-copolymer discovered in the late 1960s by Dr. Walther Grot of DuPont. Nafion is a brand of the Chemours company. It is the first of a class of synthetic polymers with ...

is a typical proton conductor in fuel cells. A jelly-like substance similar to Nafion residing in the ampullae of Lorenzini of sharks has proton conductivity only slightly lower than nafion. High proton conductivity has been reported among alkaline-earth cerates and zirconate based perovskite materials such as acceptor doped SrCeO₃, BaCeO₃ and BaZrO₃. Relatively high proton conductivity has also been found in rare-earth ortho-niobates and ortho-tantalates as well as rare-earth tungstates.

References

Electrochemistry {{Electrochem-stub