Polymer conductors, protonic

The Chemical Process Engineering Research Institute (CPERI) works on bench and pilot plant hydrogen production units, SOFCs, polymer electrolyte proton conductors, and high-temperature electrocatalytic processes. 

Similar to phosphoric acid, phosphonic acids are intrinsically proton conductive. However, phosphonic acids can he covalently attached to polymers in order to prevent leaching. Comparative studies of sulfonic acid, imidazole, and phosphonic acid functionalized model eompounds have indicated that phosphonie acids possess attractive features for applications in high-temperature PEMFCs. This has spawned extensive research in recent years to prepare and study phosphonated polymers as proton conductors under low humidity eonditions. ... 

Andreopoulou AK, Daletou MK, Kalamaras I et al (2012) Crosslinked or non-crosslirrked aromatic (co)polymers as proton conductors for use in high temperature PEM fuel cells. US Patent Application No. 13367855/02.07.2012... 

Polyvinyl fluoride (PVF) has been sulfonated by treatment of PVF films with chlorosulfonic acid. These materials provide new types of polymer-based proton conductors and the state of water in sulfonated PVF membranes has been studied by FTIR spectroscopy. ... 

Canovas, M. J., Acosta, J.L., Linares, A. (2005) Polymer thermoplastic proton conductors based on PPO and PS ionomer blends. Macromolecular Chemistry and Physics, 206, 680-688. 

Polymer Electrolyte Fuel Cell. The electrolyte in a PEFC is an ion-exchange (qv) membrane, a fluorinated sulfonic acid polymer, which is a proton conductor (see Membrane technology). The only Hquid present in this fuel cell is the product water thus corrosion problems are minimal. Water management in the membrane is critical for efficient performance. The fuel cell must operate under conditions where the by-product water does not evaporate faster than it is produced because the membrane must be hydrated to maintain acceptable proton conductivity. Because of the limitation on the operating temperature, usually less than 120°C, H2-rich gas having Htde or no (

Significant advances have been made in this decade in electrochemical H2 separation, mostly through the use of solid polymer electrolytes. Since the overpotentials for H2 reduction and oxidation are extremely low at properly constructed gas diffusion electrodes, very high current densities are achievable at low total polarization. Sedlak [13] plated thin layer of Pt directly on Nafion proton conductors 0.1-0.2cm in thickness, and obtained nearly 1200 mA/cm2 at less than 0.3 V. The... 

All of the examples of PEMs discussed within Section 3.3 unhl now have been composed of only one polymer system without any other compounds present—be they small molecules, polymers, or solid-state materials. A wide variety of different polymer blend and composite PEMs has been made. However, in this section, only a brief overview highlighting some of the more interesting examples that have been reported in the literature will be presented. Eor discussion, these types of PEMs have been divided into three categories polymer blends, ionomer-filled porous substrates and reinforced PEMs, and composite PEMs for high-temperature operation and alternative proton conductors. 

Schuster, M., Kreuer, K. D., Anderson, H. T. and Maier, J. 2007. Sulfonated poly(phenylene sulfone) polymers as hydrolytically and thermooxidatively stable proton conductors. Macromolecules 40 598-607. 

Interest in new solid polymer electrolytes has driven some research groups to investigate other materials containing proton conducting moieties aside from sulfonic acid. Polymers and copolymers from monomers containing phosphonic-based proton conductors have been reported. Phosphonic and/or phosphinic acid containing polymers have not been well studied because of the rather limited synthetic procedures available for their preparation, compared with sulfonic acid derivatives. Miyatake and Hay... 

Figure 45. Imidazole proton conductors—both as free molecules and attached to a polymer backbone.

Imidazole proton conductors have been explored as water replacement solvents and have also been attached to polymer backbones to replace the acid/ water complex in current PEMs (Figure 45). 

Proton exchange membrane fuel cell (PEMFC) working at around 70 °C with a polymer membrane electrolyte, such as Nafion, which is a solid proton conductor (conducting by the H + cation). 

Although the motion of protons does not lead to electrical conduction in the case of benzoic acid, electronic and even ionic conductivity can be found in other molecular crystals. A well-studied example of ionic conduction is a film of polyethylene oxide (PEO) which forms complex structures if one adds alkaline halides (AX). Its ionic conductivity compares with that of normal inorganic ionic conductors (log [cr (Q cm)] -2.5). Other polymers with EO-units show a similar behavior when they are doped with salts. Lithium batteries have been built with this type of... 

Two types of solid ionic conductors are of special interest—those in which metallic cations such as lithium ions can be transported across the polymer membrane, and others in which protons can move from one side of the membrane to the other. The first... 

Fig. 4.26 The elements of the hydrogen fuel cell. Note-, (i) The student is reminded that a chemical species which loses electrons is oxidized one that gains electrons, reduced, (ii) The proton H is transported through the polymer electrolyte attached to water molecules, (H20)nH which causes a water management problem. Current research is aimed at developing proton conductors able to operate in the region of 200 °C when the proton migrates unattached to water molecules.

Solid Polymer Electrolyte Fuel Cell Here, there is no apparent liquid solution, or high-temperature ionic conductor. The usual ionic solution between the electrodes is replaced by a well-humidified membrane made of a perfluorosulfonic acid polymer that conducts protons. 

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