Grotthuss

The Grotthuss-Draper law states that only light which is absorbed by a chemical entity can bring about photochemical change. 

Agmon, N. 1995. The Grotthuss mechanism. Chemical Physics Letters 244 456—462. 

Structure diffusion (i.e., the Grotthuss mechanism) of protons in bulk water requires formation and cleavage of hydrogen bonds of water molecules in the second hydration shell of the hydrated proton (see Section 3.1) therefore, any constraint to the dynamics of the water molecules will decrease the mobility of the protons. Thus, knowledge of the state or nature of the water in the membrane is critical to understanding the mechanisms of proton transfer and transport in PEMs. 

The molecular structure of water was not known in Grotthuss time, and he proposed that water molecules, designated as -+, were arranged between the positive (p) and negative (n) electrodes in the following manner p —h - H— + —h n. (J. R. Partington (1964) A History of Chemistry, vol. 4, pp. 26-27, Macmillan, London.)... 

Extended chains of hydrogen-bonded water molecules proposed by Christian von Grotthuss in the early 19th century to explain electrolyte conductance in water. ... 

COMRUTER ALGORITHMS SOFTWARE GROTTHUSS CHAINS GROTTHUSS-DRAPER LAW GROTTHUSS MECHANISM... 

Figure 2.5 Relative energetics of the Grotthuss and proton-hole-transfer mechanisms as a function of the )Ka values. (Reproduced with permission from ref. 30.)...

Figure 13.3 Proton ordering in hydrogen bonding, illustrating favorable (Grotthuss-like) ordering in a chain (above) or cyclic hexamer (a), contrasted with the unfavorable isomer (b), one of many similar that cannot survive thermodynamically. All clusters are ice rule-compliant (cf. Sidebar 5.18).

Ab initio methods provide elegant solutions to the problem of simulating proton diffusion and conduction with the vehicular and Grotthuss mechanism. Modeling of water and representative Nation clusters has been readily performed. Notable findings include the formation of a defect structure in the ordered liquid water cluster. The activation energy for the defect formation is similar to that for conduction of proton in Nafion membrane. Classical MD methods can only account for physical diffusion of proton but can create very realistic model... 

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