Electrolyte fuel cells

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 (

As can be seen from Eigure 11b, the output voltage of a fuel cell decreases as the electrical load is increased. The theoretical polarization voltage of 1.23 V/cell (at no load) is not actually realized owing to various losses. Typically, soHd polymer electrolyte fuel cells operate at 0.75 V/cell under peak load conditions or at about a 60% efficiency. The efficiency of a fuel cell is a function of such variables as catalyst material, operating temperature, reactant pressure, and current density. At low current densities efficiencies as high as 75% are achievable. 

Polymer electrolyte fuel cells can be obtained from several developers. These fuel cells deliver about 5 kW of power and measure 30 by 30 by 70 cm (12 X 12 X 28 in.). For the large produc tion volume anticipated if the automotive industry were to adopt the PEFC, a system cost of less than 100/kW may be reached eventually. 

Gottesfeld, S., and Zawodzinski, T. A. (1998). Polymer Electrolyte Fuel Cells, Advances m Electrochemical Science and Engineering, ed. R. Alkire et al. NewYork Wiley. 

A membrane ionomer, in particular a polyelectrolyte with an inert backbone such as Nation . They require a plasticizer (typically water) to achieve good conductivity levels and are associated primarily, in their protonconducting form, with solid polymer-electrolyte fuel cells. 

Solid electrolyte fuel cells have been investigated intensively during the last four decades.10,33 37 Their operating principle is shown schematically in Fig. 3.4. The positive electrode (cathode) acts as an electrocatalyst to promote the electrocatalytic reduction of O2 (g) to O2 ... 

Fuel cells such as the one shown on Fig. 3.4a convert H2 to H20 and produce electrical power with no intermediate combustion cycle. Thus their thermodynamic efficiency compares favorably with thermal power generation which is limited by Carnot-type constraints. One important advantage of solid electrolyte fuel cells is that, due to their high operating temperature (typically 700° to 1100°C), they offer the possibility of "internal reforming" which permits the use of fuels such as methane without a separate external reformer.33 36... 

In recent years it was shown that solid electrolyte fuel cells with appropriate electrocatalytic anodes can be used for chemical cogeneration i.e. for the simultaneous production of electrical power and useful chemicals. 

Table 3.1. Electrocatalytic reactions investigated in doped Zr02 solid electrolyte fuel cells for chemical cogeneration ...

R.D. Farr, and C.G. Vayenas, Ammonia High Temperature Solid Electrolyte Fuel Cell,... 

In solid electrolyte fuel cells, the challenge is to engineer a large number of catalyst sites into the interface that are electrically and ionically connected to the electrode and the electrolyte, respectively, and that is efficiently exposed to the reactant gases. In most successful solid electrolyte fuel cells, a high-performance interface requires the use of an electrode which, in the zone near the catalyst, has mixed conductivity (i.e. it conducts both electrons and ions). Otherwise, some part of the electrolyte has to be contained in the pores of electrode [1]. 

Development of a CO remover employing microchannel reactor for polymer electrolyte fuel cells... 

A miniature methanol steam reformer for polymer electrolyte fuel cell... 

Recently, rhodium and ruthenium-based carbon-supported sulfide electrocatalysts were synthesized by different established methods and evaluated as ODP cathodic catalysts in a chlorine-saturated hydrochloric acid environment with respect to both economic and industrial considerations [46]. In particular, patented E-TEK methods as well as a non-aqueous method were used to produce binary RhjcSy and Ru Sy in addition, some of the more popular Mo, Co, Rh, and Redoped RuxSy catalysts for acid electrolyte fuel cell ORR applications were also prepared. The roles of both crystallinity and morphology of the electrocatalysts were investigated. Their activity for ORR was compared to state-of-the-art Pt/C and Rh/C systems. The Rh Sy/C, CojcRuyS /C, and Ru Sy/C materials synthesized by the E-TEK methods exhibited appreciable stability and activity for ORR under these conditions. The Ru-based materials showed good depolarizing behavior. Considering that ruthenium is about seven times less expensive than rhodium, these Ru-based electrocatalysts may prove to be a viable low-cost alternative to Rh Sy systems for the ODC HCl electrolysis industry. 

Dodolet JP, Cote R, Faubert G, Denes G, Guay D, Bertrand P (1998) Iron catalysts prepared by high-temperature pyrolysis of tetraphenylporphyrins adsorbed on carbon black for oxygen reduction in polymer electrolyte fuel cells. Electrochim Acta 43 341-353... 

Gubler, L., S. A. Giirsel, and G. G. Scherer, Radiation-grafted membranes for polymer electrolyte fuel cells. Journal Fuel Cells, August 2005. 

Electrocatalysis of Oxygen Reduction in Polymer Electrolyte Fuel Cells A Brief History and a Critical Examination of Present Theory and Diagnostics... 

ELECTROCATALYSIS OF OXYGEN REDUCTION IN POLYMER ELECTROLYTE FUEL CELLS... 

Springer TE, Wilson MS, Gottesfeld S. 1993. Modeling and experimental diagnostics in polymer electrolyte fuel cells. J Electrochem Soc 140 3513-3526. 

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