Solids, proton transport

K.D. Kreuer, M. Hampele, K. Dolde, and A. Rabenau, Proton Transport in Some Heteropolyacidhydrates. A Single Crystal PRG-NMR and Conductivity Study, Solid State Ionics, 28-30,589-93 (1988). 

Fig. 2.7 Schematic representation of electrochemical processes (reduction) for organic solids able to experience coupled proton transport/electron transport processes...

In solutions and also in solids electron or proton transport may be coupled to the ionic charge transport via electron exchange reactions (- electron hopping or electron transfer reaction) or proton jumping (see - charge transfer reaction). 

S. Chandra and N. Singh, Fast-proton transport in hydrazine sulphate II. NMR linewidth and relaxation studies.. Phys. C Solid State Phys., 1983,16,3099-3103. 

Surfaces of crystals and the grain boundaries may have disordered regions where proton transport is facilitated. Adsorbed water or electrolyte solution trapped between the grains will also increase the conductivity and give rise to false conclusions concerning the solid-state nature of conductivity. Surface or liquidlike conductivity has a low activation energy ( a 0.1-0.4eV), approaching the of aqueous acidic... 

Eikerling, M Paddison, S. J., Pratt, L. R and Zawodzinski, T. A., Defect stmcture for proton transport in a triflic acid monohydrate solid. Chem. Phys. Lett. 368,... 

Fig. 1. Scheme of electron transport in oxygenic photosynthesis. The solid arrows (- ) indicate the direction of electron transport —>, proton transport across the thylakoid membrane ------------>, light re-... 

Pietraszko, A., Hilczer, B. and Pawlowski, A. (1999). Structural aspects of fast proton transport in (NH4)3H(Se04)2 single crystals. Solid State Ionics 119, 281-288. 

R.Y. Yeo, Ion clustering and proton transport in Nafion membranes and its applications as solid polymer electrolyte, J. Electrochem. Soc., 1983, 130, 533-538. 

For structuring, the IL has to be immobilised. This can be done using i.e. zeolitic structures or molecular sieves. It is obvious that with increasing surface area of the solid phase, the motion of the liquid and the proton transport will be hindered. From polymerisation experiments it is known that the stiffening of polymers by cross-linking can be compared with the polymer-surface interaction. Electrode surfaces and solids such as silica, carbon black or cathode powder also stiffen the polymer [52]. This can be explained by different transport properties at the interfaces. As a consequence it must be expected that at the surface of the added particles the ionic liquid will behave in a different way than in the immobilised liquid phase. 

Applications of solid state NMR along with FTIR and Raman spectroscopy and X-ray crystallography to study the structural changes in the proton transport cycle of the light-driven pump, bacteriorhodopsin, have been reviewed by Laniy. " ... 

Subbaraman R, Ghassemi H, Zawodzinski Jr T. Triazole and triazole derivatives as proton transport facilitators in polymer electrolyte membrane fuel cells. Solid State Ionics 2009 180(20-22) 1143-50. 

S. W. Smoot, D. H. Whitmore and W. P. Halperin, Influence of stoichiometry and the nature of the spinel-block stabilizing element on proton transport behavior in solid electrolyte with the p"-alumina structure, Solid States Ionics 18/19 (1986) 687-93. 

The transport properties of perfluorosulphonic membranes are largely influenced by the water content of the membrane, particularly when the membrane is in the acid form. In the dry state, the Nafion membrane behaves like an insulator but, when hydrated, the membrane becomes conductive as a function of the water content. Yeo established that the minimum threshold corresponds to about six molecules of water per sulphonic site, whereas Pourcelly et al. estimated about seven molecules. Randin has shown that membranes with six molecules of water per sulphonic site have suflicient conductivity for use as a semi-solid proton... 

Quantitative data on bulk proton transport are required especially for the understanding of proton transport mechanisms (see Chapters 29 31) including the implications for the use of solid proton conductors in operational electrochemical cells (see Chapters 32 39). 

There is no standard procedure for the measurement of proton conductivity and experimental techniques as well as structural and chemical considerations have to be adapted to the material under investigation. There are some peculiar features common to most solid proton conductors which make it difficult to identify the proton as the charge carrier, to determine its accurate conductance (self diffusion) and to separate bulk proton transport from artefacts (such as transport along surfaces, grain boundaries, domain walls, dislocations, second phases). How to cope with these will be discussed in the following section. 

---