Fuel cell electrolyte materials

Watakabe, A. 2005. Polymer electrolyte fuel cell, electrolyte material therefore and method for its production. US Patent 2005037265. 

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. 

Observations In order to be effective as a solid polymer electrolyte fuel cell, the material... 

Recently, the Pt NMR of commercial fuel cell electrode material has been observed 180,181) (Fig. 61). This material consists of platinum supported on carbon black and pressed into graphitized-carbon cloth. (Similar material has been used to study NMR see Section IV.G.) Because of the conducting nature of the carrier, one might expect to see differences with respect to NMR of particles supported on oxides. Furthermore, if an electrolyte is present in the NMR sample, the electric double layer at the metal/electrolyte interface might influence the Pt surface signal. 

Fuel cell Electrolyte Electrodes (anode/cathode) Interconnector Construction materials... 

Arendt, R.H. Alternate matrix materials for molten carbonate fuel cell electrolyte structures. J. Electrochem. Soc. 1982, 129 (5), 979-983. 

Shoji, C. Matsuo, T. Suzuki, A. Yamamasu, Y. Development of electrolyte plate for molten carbonate fuel cell. In Materials for Electrochemical Energy Storage and Conversion II— Batteries, Capacitors and Fuel Cells, Materials Research Society Symposium Proceedings, 1998 Vol. 496, 211-216. 

Protonated Chalcogenide Materials for Fuel Cell Electrolyte Membranes, poster at the 104th Annual Meeting and Exposition of the American Ceramic Society, Steve W. Martin, Steven A. Poling, and Jacob T. Sutherland, St. Eouis, MO, April 29-May 1, 2002. 

As documented in and expressed by these various contributions, the topic Polymers for Fuel Cells is a vast one and concerns numerous synthetic and physico-chemical aspects, derived from the particular application as a solid polymer electrolyte. In this collection of contributions, we have emphasized work which has already led to tests of these polymers in the real fuel cell environment. There exist other synthetic routes for proton-conducting membrane preparation, which are not discussed in this edition. Furthermore, certain polymers are utilized as fuel-cell structure materials, e.g., as gaskets or additives (binder, surface coating) to bipolar plate materials. These aspects are not covered here. 

In fuel cells, however, more expensive materials are employed even though their amount can be tremendously reduced. The total geometric surface area of the cells shows a 30-fold decrease due to higher current densities obtained with more conductive fuel cell electrolytes. Fuel cells can be built in a bipolar construction with cells stacked in series with the negative current collector of one cell serving as the positive current collector of the adjacent cell. Fuel cells require a hydrogen tank and an air compressor which makes their balance of plant more complex. 

Polyvinylidene fluoride, is a fluorinated semi-crystalline thermoplastic which has a continuous use service temperature of up to 150 °C and a very low dielectric constant. Current manufacturers include Arkema which has become legally separated from its former owner. Total. PVDF applications include its use as fuel cell membrane material, film material in capacitors and as electrolyte material in sodium sulfur batteries. In the US, NASA has employed a crosslinked polystyrene sulfonic acid (PSSA)/PVDF composite as a PEM. 

Other fuel cell membrane materials include modified polybenzimidazole. In the US researchers have developed rod-coil block copolyimides which exhibit high levels of ionic conduction and which can be made into dimensionally stable solid electrolyte fuel cell membranes. These membrane materials are also suitable for use in lithinm-ion electrochemical cells. 

Investigations into the behaviour of ionic solids are important in the search for new battery and fuel cell electrolytes. Defects, plastic phases, disorder and polymorphism in crystalline solids (and their association with ionic conductivity) and associated solid-solid equilibria are thus of considerable interest. The basis of our understanding of these phenomena and their relationship to the characteristics of the con5)onent ions includes studies of materials that are ionic liquids. 

The SOFC is a complete solid-state device that uses an oxide ion-conducting ceramic material as the electrolyte. The electrolyte is a nonporous solid, such as Y2O3 stabilized Zr02 with conductivity-based oxygen ions [122, 128, 142-144]. Yttria-stabilized zirconia (YSZ) is the most commonly used material for the electrolyte. It was first used as a fuel cell electrolyte by Baur and Preis in 1937 [145]. The anode is usually made of a C0-Z1O2 or Ni-Zr02 cement [13, 95, 146, 147], while the cathode is made of Sr-doped LaMnOs (LSM) [13,148-150],... 

Aging mechanisms of polymer electrolyte membrane fuel cell (PEMFC) materials and perfomnance decay why physical modelling ... 

Li, Y., Rui, Z., Xia, C., Anderson, M and Lin, Y.S. (2009) Performance of ionicconducting ceramic/carbonate composite material as solid oxide fuel cell electrolyte and CO2 permeation membrane. Catal. Today, 148, 303-309. 

Recently, a full consensus standard for the Determination of Fracture Toughness of Advanced Ceramics at Ambient Temperature was developed and published under the auspices of ASTM [4]. During development of the standard test method, typical interferences were addressed, and when possible each error was kept to 2% or less. In addition to development of the standard, several round robin exercises were run [5 9], and a standard reference material was developed [10]. Additional work on fracture toughness standardization should include a method(s) for elevated temperature testing, very thin shapes such as fuel cell electrolyte membranes, and miniaturized test specimens. 

The first perfluorinated ionomer was developed in the early 1960s by Walther G. Grot at E.I. DuPont de Nemours (Grot, 2011). It became famous under the trade-name Nafion. From the mid-1960s, Nafion found use as an electrochemical separator material in the chlor-alkali industry. Exploration of Nafion as a fuel cell electrolyte started at about the same time. 

The ohmic loss is inversely proportional to conductivity so developing high-conductivity electrodes and electrolyte materials is critical. From the above examples, we know that ionic charge transport in the electrolyte accounts for most of the ohmic loss. However unfortunately, the development of satisfactory ionic conductors is still challenging because a good fuel cell electrolyte must have high ionic conductivity and stability at the same time. The three most widely used material classes for fuel cells are aqueous electrolytes, polymer electrolytes and ceramic electrolytes. 

Ce02 host is substituted with either Sm or Gd (Cei-jcSm Oz Sj CSO, and Cei Gd 02 5, CGO), creating significant vacancy concentrations. Use of these ceria-based materials is limited by the redox characteristics of the Ce3+/4+ couple, with reduction occurring at temperatures above about 650 °C leading to a reduction of the ionic transport number. This in turn can lead to short circuits within the cell and hence a loss of performance. However, as conductivity in ceria-based compounds is sufficient at temperatures below 650 °C for fuel cell electrolytes, the issue is then one of suitably active cathodes, addressed in Section 2.1.3. 

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