Proton transport in nafion

Choi, P. Jalani, N.H. Datta, R. Thermodynamics and proton transport in Nafion II. Proton diffusion mechanisms and conductivity. J. Electrochem. Soc. 2005, 152 (3), E123-E130. 

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. 

Hwang, G. S. Kaviany, M. Gostick, J. T. Kientiz, B. Weber, A. Z. Kim, M. H., Role of Water States on Water Uptake and Proton Transport in Nafion Using Molecular Simulations and Bimodal Networks. Polymer 2011,52,2584-2593. 

Thompson, E.L., Capehart, T.W., Fuller, T.J., and Jome, J. (2006) Investigation of low-temperature proton transport in Nafion using direct current conductivity and differential scanning calorimetry, J. Electrochem. Soc., 153, A2351-A2362. 

Choi P, Jalani N H and Datta R (2005) Thermodynamics and Proton Transport, Nafion, III. Proton Transport in Nafion/ Sulfated Zr02 Nanocomposite Membranes, J. Electrochem. Soc., 152, pp. A1548-A1554. 

Theoretical Views of Proton Transport in Aqueous Systems and in Hydrated Nafion Membranes... 

In a H2/air fuel cell, the protons produced at the anode side need to be transferred to the cathode side to react with 02. This requires a proton transport electrolyte. Nafion membranes, composed of a perfluorosulfonated polymer, are the most commonly used polymer electrolyte membranes to conduct protons. The structure of the Nafion membrane is shown in Figure 1.5. Nafion can take on a... 

Investigate additives to extend the stable performance of Nafion membranes to 120°C create a new class of ionizable materials that enable proton transport in the absence of water (150°C operation)... 

A precondition for proton conductivity in Nafion is uptake of sufficient water into the membrane and prevention of its drying out during operation. The protons diffuse through water channels in the membrane to the cathode or are transported... 

Figure 10.4. Model systems to study proton transport in slab pores. Top rigid slab with embedded 803 head groups. Bottom slab boundary in a Nafion side-chain model. Proton complexes are coloured according to internal structure blue H30 -like (Eigen complexes), green H502 -like (Zundel complexes).

The MD simulations of proton transport in model pores employing empirical valence bond interaction models described the pore surface in a similar fashion as a regular array of static sulfonate groups, rotationally mobile or tethered sulfonate groups, or as entire Nafion sidechains [83,84],... 

Since the discovery of conductivity in ice in the last century, proton transport in solids has aroused great scientific interest. Synthesis of Nafion Perfluorocarbon sulphonic acid poly-... 

Ionic current between the anode and the cathode is transported through an ionic conductor. In low-temperature fuel cells, internal charge carriers are protons and the proton conductor is a solid polymer electroljde membrane (typically Nafion ). It took more than 10 years to clarify the mechanism of proton transport in this membrane. However, the membrane structure and its dependence on water content are still unclear. 

Paddison SJ, Paul R (2002) The nature of proton transport in fully hydrated nafion. Phys Chem Chem Phys 4 1158-1163... 

FIGURE 5.15 In situ method for measuring proton conductivity in Nafion membrane by using EC-AFM. The applied voltage induces water oxidation at the electrode. TTie protons are only transported through the membrane when the conductive AFM tip makes contact with an ion channel. These protons are used for the ORR at the AFM tip. [11,66,67]. (For color version of this figure, the reader is referred to the online version of this hook.)... 

The most common electrode design currently employed is the thin-film design, characterized by the thin Nafion film that binds carbon-supported catalyst particles. The thin Nafion layer provides the necessary proton transport in the catalyst layer. However, this is a significant improvement over the PTFE-bound catalyst layer, which requires the less effective impregnation of Nafion . Sputter deposited catalyst layers have been shown to provide some of the lowest catalyst loadings, as well as the thinnest layers. The short conduction distance of the thin sputtered layer dissipates the requirement of a proton-conducting medium, which can simplify production. The performance of the state of the art sputtered layer is only slightly lower than that of the present thin-film convention [125]. 

Fig. 7 Schematic of proton transport in and through Nafion membranes. Protons are generated by hydrogen oxidation on a catalyst surface. The protons move laterally in the catalyst layer (uniform potential field) until they find an opening into the hydrophilic domains of the Nafion. The protons are transported across the membrane by electric field-assisted motion. At low applied potentials, the transport across the membrane is limiting, but at high applied potentials, the proton motion is limited by diffusion in the catalyst layer to the openings of the hydrophilic domains...

Paddison, S.J., Paul, R. (2002) The namre of proton transport in fully hydrated Nafion . Physical Chemistry Chemical Physics, 4, 1158-1163. 

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