Perfluorosulphonic acid

Fig. 13.2 Structure of perfluorosulphonic acid co-polymer (Nation ). The Yeager Three Phase Model, based on a three-phase clustered system with interconnecting channels within the polymer. (a) Fluorocarbon backbone, (b) interfacial region of relatively large fractional void volume containing some pendant side chains, some water and sulphate groups, (c) clustered regions...

Yeo, R.S., Dual cohesive energy densities of perfluorosulphonic acid (Nafion) membrane, Polymer, 21, 432, 1980. 

Dupont de Nemours) or analogous perfluorosulphonic acid membranes have been the dominating choice. The structure of the repeat structure of the polymer fluorocarbon backbone and a side chain with sulphonic acid ends upon which Nafion is based is shown in Fig. 3.42 (the commercial product is sold with various thicknesses and dimensions denoted by a number code such as "Nafion-117", related to non-SI units). The membranes should have high protonic conductivity, low gas permeability and, of course, a suitable mechanical strength and low temperature sensitivity. 

Anodic oxidation of iodoperfluoroalkanes in the presence of perfluorosulphonic acids leads to the production of perfluoroalkyl perfluoroalkanesulphonate esters in good yields393. 

T. A. Zawodzinski Jr., S. Gottesfeld, S. Shoichet, and T. J. McCarthy, The Contact Angle between Water and the Surface of Perfluorosulphonic Acid Membranes, Journal of Applied Electrochemistry, 23, 86 (1993). 

Nafion is the leader of perfluorosulphonic proton conductors. Produced by Dupont de Nemours, it is commercially available in different forms homogeneous or reinforced membranes, powders, tubes and solutions. From solutions of perfluorosulphonic acid or salt in organic solvents, gels and films can also be made. From Nafion , many kinds of composite material may also be prepared either by including small, dispersed particles inside the polymeric phase or by using it to coat solid electronic conductors. The adhesive power of this material is important when it is maintained in contact with a wide variety of supports. 

Electrodes coated with a perfluorosulphonic acid Nafion membrane can be used to inject protons into non-aqueous media and enable one to exercise additional control on the course of an electro-organic process in which the proton transfer reaction plays an important role . 

Zawodzinski TA, Gottesfeld S, Shoichet S, McCarthy TJ. The contact angle between water and the surface of perfluorosulphonic acid membranes. J Appl Electrochem 1993 23 86-8. 

Figure 4.4 Example structure of a sulphonated fluoroethylene (also called perfluorosulphonic acid PTFE copolymer).

Ren X. and Gottesfeld S. (2001) Electro-osmotic drag of water in a poly(perfluorosulphonic acid) membrane . Journal of the Electrochemical Society, 148(1), A87-A93. 

The cell design employed (Fig. 9.13) is based on a simple parallel-plate design. The anodes and cathodes are divided by a perfluorosulphonic acid exchange membrane which prevents an otherwise drastic loss of current efficiency due to the parasitic redox shuttle ... 

Abstract This chapter describes the use of molecular dynamics (MD) simulations to understand structure and transport processes in polymer electrolytes for energy storage and conversion applications. For batteries, the polymer electrolytes studied with MD techniques have generally been of poly(ethylene oxide) (PEO)-type, while the fuel cell polymer electrolytes have been perfluorosulphonic acid (PFSA) membrane materials. The MD methodology, its benefits and its limitations are explained in the chapter, together with a review of some significant MD studies of polymer electrolytes. 

Key words computational chemistry, molecular dynamics, poly(ethylene oxide), Li mobility mechanism, perfluorosulphonic acid membranes. Nation, proton transport, battery, fuel cell. 

Polymer electrolytes for fuel cells perfluorosulphonic acid systems... 

The polymer electrolytes used for low-temperature proton exchange membrane fuel cells (PEMFCs) are fundamentally different from the polymer electrolytes used in batteries. Here, the polymer is a medium for a solvent, normally water, and it is mainly in the solvent that ion transport occurs. The polymer serves several functions, of which the most important is to provide mechanical stability and electrode separation in the fuel cell application. Since the fuel cell needs proton transport from the anode to the cathode, the polymer also contains proton donating groups, often sul-phonic acid (-SO3H). The prototype PEMFC membrane materials have been perfluorosulphonic acids (PFSAs), of which the most established membrane material is Nafion (Fig. 8.8). These consist of hydrophobic teflon -CF2-CF2- backbones, with fluorinated hydrophilic and acidic side-chains for Nafion -0CF2CF(CF3)0CF2Cp2S03H. 

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