Proton polymer electrolytes

The research into proton conducting polymer electrolytes has consistently increased in recent years due to the transport characteristics which make them promising for various electrochemical applications of interest for the electronics market, including sensors and, particularly, fuel cells [113]. Nevertheless, the proton conductivity of the known polymer systems still remains below the upper limit of proton conductivity in liquids. The major problems arise from the numerous additional requirements, other than proton conductivity, which must be met for any specific application. 

In general, the ionic transport in linear or crosslinked swollen polymers containing a low molecular weight polar or ion-chelating additive mainly occurs in the solvent phase [118, 120]. This concept has been applied to develop proton conducting polymeric gel or hydrogel membranes [121-123] which reach conductivity values around 10 S cm at room temperature and are not destroyed or dissolved even at high humidity levels. 

As for most of the other advanced systems, these new protonic gel-type membranes appear to be still under evaluation. Presently, Nafion and related membranes still dominate the fuel cell market. The limited length of this chapter and its focus on batteries does not allow inclusion of a description of the present status of the polymer electrolyte fuel cells. The interested reader is referred to the many books and review articles available on the subject [e.g., 113,126,127]. 

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Gautierluneau L, Denoyelle A., Sanchez J.Y., Poinsignon C. Organic iorganic protonic polymer electrolytes as membrane for low-temperature fuel-cell. Electrochim. Acta 1992 37(9) 1615-1618... 

Gautier-Luneau, I., A. DenoyeUe, J. Y. Sanchez, and C. Poinsignon, 1992. Organic-inorganic protonic polymer electrolytes for low-temperature fuel cell. Electrochim... 

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 (

The most promising fuel cell for transportation purposes was initially developed in the 1960s and is called the proton-exchange membrane fuel cell (PEMFC). Compared with the PAFC, it has much greater power density state-of-the-art PEMFC stacks can produce in excess of 1 kWA. It is also potentially less expensive and, because it uses a thin solid polymer electrolyte sheet, it has relatively few sealing and corrosion issues and no problems associated tvith electrolyte dilution by the product water. 

Ren, X. Springer, T. E. and Gottesfeld, S. (1998). Direct Methanol Fuel Cell Transport Properties of the Polymer Electrolyte Membrane and Cell Performance. Vol. 98-27. Proc. 2nd International Symposium on Proton Conducting Membrane Euel Cells. Pennington, NJ Electrochemical Society. 

Figure 8.31. Principle of a Polymer Electrolyte Membrane (PEM) fuel cell. A Nation membrane sandwiched between electrodes separates hydrogen and oxygen. Hydrogen is oxidized into protons and electrons at the anode on the left. Electrons flow through the outer circuit, while protons diffuse through the...

The electrocatalytic oxidation of methanol has been widely investigated for exploitation in the so-called direct methanol fuel cell (DMFC). The most likely type of DMFC to be commercialized in the near future seems to be the polymer electrolyte membrane DMFC using proton exchange membrane, a special form of low-temperature fuel cell based on PEM technology. In this cell, methanol (a liquid fuel available at low cost, easily handled, stored, and transported) is dissolved in an acid electrolyte and burned directly by air to carbon dioxide. The prominence of the DMFCs with respect to safety, simple device fabrication, and low cost has rendered them promising candidates for applications ranging from portable power sources to secondary cells for prospective electric vehicles. Notwithstanding, DMFCs were... 

Membrane-type fuel cells. The electrolyte is a polymeric ion-exchange membrane the working temperatures are 60 to 100°C. Such systems were first used in Gemini spaceships. These fuel cells subsequently saw a rather broad development and are known as (solid) polymer electrolyte or proton-exchange membrane fuel cells (PEMFCs). 

Figure 4.1 Schematic of the atomic structure of the active three-phase interface between the metal particle that catalyzes the reaction, the carbon support necessary to conduct electrons, and the polymer electrolyte and solution necessary to conduct protons for electrocatalytic systems.

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... 

Rusanov, A.L., Likhatchev, D., Kostoglodov, P.V., Mullen, K. and Klapper, M. Proton-Exchanging Electrolyte Membranes Based on Aromatic Condensation Polymers. Vol. 179, pp. 83-134. 

Bridged polysilsesquioxanes having covalently bound acidic groups, introduced via modification of the disulfide linkages within the network, were studied as solid-state electrolytes for proton-exchange fuel cell applications.473 Also, short-chain polysiloxanes with oligoethylene glycol side chains, doped with lithium salts, were studied as polymer electrolytes for lithium batteries. 

PEM Proton-exchange-membrane fuel cell (Polymer-electrolyte-membrane fuel cell) Proton- conducting polymer membrane (e.g., Nafion ) H+ (proton) 50-80 mW (Laptop) 50 kW (Ballard) modular up to 200 kW 25-=45% Immediate Road vehicles, stationary electricity generation, heat and electricity co-generation, submarines, space travel... 

PAFC PEMFC PFC PGM PHEV PISI PM POX ppm PPP Phosphoric-acid fuel cell Proton-exchange-membrane fuel cell Polymer-electrolyte membrane Perfluorocarbons Platinum-group metals Plug-in hybrid-electric vehicle Port-injection spark ignition Particulate matter Partial oxidation Parts per million Purchasing power parity... 

X-Ray Photoelectron Investigation of Phosphotungstic Acid as a 159 Proton-Conducting Medium in Solid Polymer Electrolytes Clovis A. Linkous, Stephen L. Rhoden, and Kirk Scammon... 

Zawodzinski, T. A., Davey, J., Valerio, J. and Gottesfeld, S. 1995. The water-con-tent dependence of electro-osmotic drag in proton-conducting polymer electrolytes. Electrochimica Acta 40 297-302. 

Jeske, M., Soltmann, C., Ellenberg, C., Wilhelm, M., Koch, D. and Grathwohl, G. 2007. Proton conducting membranes for the high temperature-polymer electrolyte membrane-fuel cell (HT-PEMFC) based on functionalized polysiloxanes. 

Buchi, F. N., Gupta, B., Haas, O. and Scherer, G. G. 1995. Performance of differently cross-linked, partially fluorinated proton-exchange membranes in polymer electrolyte fuel cells. Journal of the Electrochemical Society 142 3044—3048. 

Gasa, J. V., Weiss, R. A. and Shaw, M. T. 2006. Influence of blend miscibility on the proton conductivity and methanol permeability of polymer electrolyte blends. Journal of Polymer Science Part B 44 2253-2266. 

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