Conduction mechanisms in materials with volatile molecules

The peculiarity of proton transport in aqueous solutions was recognized early on by the exceptionally high limiting equivalent conductivity of the proton (350 cm at 25 °C ) compared to that of any other monovalent cation, data for which fall into a very narrow range (39, 50, 74, 78, 77, 74 cm Q -1 for Li+, Na-, K+, Cs-, Rb+, at 25 C ). The latter similarity is a direct consequence of cation solvation by water molecules, which diffuse at approximately the same rate (2.26 x 10 cm s at 25 °C). 

The earliest ideas about proton conduction in aqueous solutions were stimulated by considerations of the electrolytic decomposition of water in 1806. Grotthuss postulated chains of water dipoles along which electricity may be transported. One basic step which is part of any proton conduction mechanism formulated since the early days of physical chemistry had already been described by several authors at the beginning of this century . They recognized that intermolecular proton transfer can lead to charge transport at a rate exceeding that of other species. The first formal theory was attempted by Huckel in 1928 at a time when the existence of a discrete H30 ion had already been suspected. Huckel treated this species as a dipole and tried to calculate its reorientational rates into positions favourable for proton transfer to neighbouring water molecules. A first quantum mechanical theory of intermolecular proton 

1 Proton conduction mechanism in dilute acidic aqueous solutions 

All the models presented so far lack quantitative experimental verification. Common to most mechanisms is that the equivalent conductivity of protons (Ah+) is thought to be composed of a so-called normal conductivity, i.e. the diffusion of H30 ions (Ahjo ) td a so-called extra conductivity which are thought to be mutually independent. 

This is most likely an invalid assumption considering the temperature 

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Kreuer KD (1992) Conduction mechanisms in materials with volatile molecules. In Colomban P (ed) Proton Conductors. Cambridge University Press, Cambridge, p 474 Schmidt TJ, Baurmeister J (2006) ECS Trans 3 1 861... 

Conduction mechanisms in materials with volatile molecules... 

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