Proton conduction mechanisms

Hence, the two main foci of this review are (i) the current understanding of the underlying elementary processes and (ii) a phenomenological description of the resulting macroscopic transport phenomena. Because the first aspect comprises proton conduction mechanisms other than the mechanisms of parasitic transport , this review may also be considered an... 

Proton-conduction mechanisms that occur in the aforementioned proton solvents, when present as a homogeneous phase and as a component of heterogeneous fuel cell separator materials, are described more specifically in the following two sections. 

Phosphoric Acid. Although the proton conduction mechanism in phosphoric acid has not been investigated to the same extent, it is evident that the principal features exhibit similarities, along with important differences. 

Figure 3. Proton conduction mechanism in iiquid imida-zoie, as revealed by a Car—Parrinello molecular dynamics (CPMD) simulation.3 Note the similarities with the proton conduction mechanism in water (see Figure 1).

Heteropolyacids are frequently used to modify proton-conducting composites,or they are just dispersed in inert matrixes.However, because the proton conduction mechanism of such hydrated salts is similar to those of hydrated polymeric sys-tems, these composites show qualitatively similar transport properties. The same is true for organically modified inorganic layered compounds such as titanium phosphate sulfophenylenphosphonate, the conductivity of which is dependent on the RH value, in a manner similar to that observed with Nafion. ... 

Paddison SJ (2003) Proton conduction mechanism at low degrees of hydration in sulfonic acid-based polymer electrolyte membranes. Ann Rev Mater Res 33 289-319 Rasten E, Hagen G, Tunold R (2003) Electrocatalysts in water electrolysis with solid polymer electrolyte. Electrochimica acta 48 3945-3952... 

Abstract. Nanopowders of nonstoichiometric tungsten oxides were synthesized by method of electric explosion of conductors (EEC). Their electronic and atomic structures were explored by XPS and TEM methods. It was determined that mean size of nanoparticles is d=10-35 nm, their composition corresponds to protonated nonstoichiometric hydrous tungsten oxide W02.9i (OH)o.o9, there is crystalline hydrate phase on the nanoparticles surface. After anneal a content of OH-groups on the surface of nonstoichiometric samples is higher than on the stoichiometric ones. High sensitivity of the hydrogen sensor based on WO2.9r(OH)0.09 at 293 K can be connected with forming of proton conductivity mechanism. 

At the comparison of the Ols-spectra of the samples MS2 and NN2 it is seen (Fig. 3-2, Fig. 3-4, Table 1), that after anneal on air the OFF/O2 - ratio in the nonstoichiometric sample of tungsten oxide is higher than in the stoichiometric sample. High concentration of the OH -groups on the active element s surface can form a proton conductivity mechanism and cause a high sensitivity of the hydrogen sensor based on W02.9i (OH)0.09 nanoparticles at 293 K. 

The energy released by electron transfer can be used in the transport of protons through the membrane. One of the proton conduction mechanisms in proteins is through a chain of hydrogen bonds in the protein, i.e. a Grotthus mechanism (Section 2.9), similar to the mechanism of proton movement in ice. Protons are injected and removed by the various oxidation/reduction reactions which occur in the cell there is no excess of protons or electrons in the final balance, and the reaction cycle is self-sustaining. 

Any proton-conduction mechanism in which the rate-determining step involves the breaking of hydrogen bonds would succeed equally well in explaining the heat of activation and alcohol anomalies, but not the... 

Park, J.-H., Possible origin of the proton conduction mechanism of CSH2PO4 crystals at high temperatures, Phys. Rev. B, 69, 54104-1-6 (2004). 

Krimm, S., and Dwivedi, A. M., Infrared spectrum of the purple membrane Clue to a proton conduction mechanism . Science 216, 407-408 (1982). 

FIGURE 8-8 Proposed proton conductance mechanism (423). Left, before rotation. Middle, doubly filled H bond. Right, after rotation. 

S.J. Paddison. Proton conduction mechanisms at low degrees of hydration in sulfonic acid-based polymer electrol3de membranes. 

Structural models emerge from the notion of membrane as a heterogenous porous medium characterized by a radius distribution of water-filled pores. This structural concept of a water-filled network embedded in the polymer host has already formed the basis for the discussion of proton conductivity mechanisms in previous sections. Its foundations have been discussed in Sect. 8.2.2.1. Clearly, this concept promotes hydraulic permeation (D Arcy flow [80]) as a vital mechanism of water transport, in addition to diffusion. Since larger water contents result in an increased number of pores used for water transport and in larger mean radii of these pores, corresponding D Arcy coefficients are expected to exhibit strong dependencies on w. 

R.E. Lechner (2001). Solid State Ionics, 145, 167-177. Proton conduction mechanism in MjH(X04)2 crystals the trigonal asymmetric hydrogen bond model. 

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