Electrolytes for Fuel Cells

W. Gopel, and H.-D. Wiemhofer, Electrode kinetics and interface analysis of solid electrolytes for fuel cells and sensors, Ber. Buns. Phys. Chem. 94, 981-987 (1990). 

Fhosphoric acid does not have all the properties of an ideal fuel cell electrolyte. Because it is chemically stable, relatively nonvolatile at temperatures above 200 C, and rejects carbon dioxide, it is useful in electric utility fuel cell power plants that use fuel cell waste heat to raise steam for reforming natural gas and liquid fuels. Although phosphoric acid is the only common acid combining the above properties, it does exhibit a deleterious effect on air electrode kinetics when compared with other electrolytes ( ) including such materials as sulfuric and perchloric acids, whose chemical instability at T > 120 C render them unsuitable for utility fuel cell use. In the second part of this paper, we will review progress towards the development of new acid electrolytes for fuel cells. 

T.A. Zawodzinski, T.A. Springer, F. Uribe, S. Gottesfeld, "Characterization of Polymer Electrolytes for Fuel Cell Applications," Solid State Tonics 60, pp. 199-211, North-Holland, 1993. 

A second class [ 16] is one that may enjoy increased interest in the future because of the presence of one of its members in the first industrial IL process [lb], and also because of the new finding that its members can have aqueous solution-like conductivities [17] and can serve as novel electrolytes for fuel cells [18]. This class is closely related to the first but differs in that the cation has been formed by transfer of a proton from a Br0nsted acid to a Br0nsted base. The process is reversible, depending on how large the free energy of proton transfer is. When the gap across which... 

The evaluation of ILs as electrolytes for fuel cell has already been done. Wata-nabe et al. tested the power generation of the hydrogen/oxygen fuel cell by using a... 

Azad, A.M., Larose, S., and Akbar, S.A., Review bismuth oxide-based solid electrolytes for fuel cells, J. Mater. Sci., 29, 4135 151 (1994). 

Hasiotis, C. et al.. Development and characterization of acid-doped polybenzimid-azole/sulfonated polysulfone blend polymer electrolytes for fuel cells, J. Electrochem. Soc., 148, A513, 2001. 

A. Schechter and R.F. Savinell. Imidazole and 1-methyl imidazole in phosphoric acid doped polybenzimidazole, electrolyte for fuel cells. Solid State Ionics 147, 181-187 2002. 

Stabilized Zr02 has recently become a subject of interest as a solid electrolyte for fuel cells. Concentration cells with a solid electrolyte can be used for determining the concentration of oxygen in gaseous or liquid media at high temperatures. Solid electrolytes may also be used in the deoxidation of melted metals, removal of oxygen from gaseous mixtures, etc. 

In recent years, many papers have reported the preparation of cation exchange membranes by this method to obtain solid polymer electrolytes for fuel cells. 

A simple method to prepare the membrane is to react directly fluorosulfonyl difluoroacetyl fluoride, FS02CF2C0F, with lithium bis(trimethylsilyl)-amide, (CH3)3SiNLiSi(CH3)3, and to cross-link with multivalent cations.209 Furthermore, ceramic membranes (P205-Si02 glass membrane) prepared by the sol-gel method have been examined as proton conducting electrolytes for fuel cells.210... 

M. Yoshitake, Kotai Denkaishitsu Nenryou Denchi no Kaihatsu to Jitsuyoka (Development and Practical Utilization of Solid Polymer Electrolyte for Fuel Cell), Gijutsu Joho Kyokai, Tokyo 1999, Ch. 4, p. 65. 

The first evaluation of ILs as electrolytes for fuel cells has just been done [25]. This appears to have been the first attempt to apply ILs under aprotic conditions. 

Y. S. Kim, B. Einsla, M. Sankir, W. Harrison, and B. S. Pivovar. Stracture-property-performance relationships of sulfonated poly(arylene ether sulf-one)s as a polymer electrolyte for fuel cell applications. Polymer, 47(11) 4026 035, May 2006. 

This material can be used as polymer electrolytes for fuel cells [100], The polymers exhibit a superior thermal and chemical stability and a good solubility in many aprotic solvents. 

Potrekar RA, Kulkami MP, Kulkarni RA, Vemekar SP. Polybenzimidazoles tethered with Wphenyl 1,2,4-triazole units as polymer electrolytes for fuel cells. J Polym Sci Part A Polym Chem 2009 47(9) 2289-303. 

The conduction in BaCeOa-based ceramics is partly protonic and partly oxide ionic, when they are used as a solid electrolyte for fuel cells above 8(X) °C . 

Owing to the fact that valence electrons determine bonds, the electrical properties of a material are related to the bond type. In conductors such as metals, alloys, and intermetallics, the atoms are bound to each other primarily by metallic bonds, and metals such as tungsten or aluminum are good conductors of electrons or heat. Covalent bonds occur in insulators such as diamond and silicon carbide and in semiconductors such as silicon or gallium arsenide. Complexes and salts have ions that are bound with electrostatic forces. Ionic conductors can be used as solid electrolytes for fuel cells because solids with ionic bonds may have mobile ions. Most polymers have covalent bonds in their chains but the mechanical... 

Rana UA, Forsyth M, MacFarlane DR, Pringle JM (2012) Toward protic ionic liquid and organic ionic plastic crystal electrolytes for fuel cells. Electrochim Acta 84 213-222... 

More recently, Angell et al. have used mixtures of ammonium salts with organic anions, such as EAN with ammonium trifluoroacetate, to produce electrolytes for fuel cells suitable for operation between 100 and 200 °C. An advantage of these electrolytes over aqueons ones is that they can be neutral, unlike aqueous electrolytes, which are either acidic or basic, and hence, there are more possible catalysts that can be used and cell designs can be simpler. 

Phosphoric Acid, an Electrolyte for Fuel Cells - Temperature and Composition Dependence ofVapor Pressure and Proton Conductivity... 

Therefore, the requirement for active management of the PEM water content adds considerable system cost, complexity, and unreliability. Because of this, there is considerable research under way addressing the development of alternative classes of acid-based polymer electrolytes for fuel cells. There are excellent reviews of the progress being made in the development of these alternative polymer electrolytes [22]. 

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