Solid electrolytes, applications fuel cell

T. Hibino, H. Ishikawa, and S. lio, in Solid electrolytic type fuel cells for generating electricity stablely at 600°C , Application JP, 2004. 

A key factor in the possible application of oxygen ion conducting ceramics is that, for use as solid electrolyte in fuel cells, batteries, oxygen pumps or sensors, their electronic transport number should be as low as possible. Given that the mobilities of electronic defects typically are a factor of 1000 larger than those of ionic defects, a band gap of at least 3 eV is required to minimize electronic contributions arising from the intrinsic generation of electrons and holes. 

Fast ionic conductors are used as solid electrolytes in fuel cells and sensors. The search for fast ion conductors operating near room temperature is a matter of current electronic materials research. The practical small-scale application of some types of fuel cells as replacements for batteries may hinge on success in this search. 

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. 

Poltarzewski, E., Stoiti, R, Alderucci, V., Wieczorek, W., and Giordano, N. Nation distribution in gas diffusion electrodes for solid polymer electrolyte membrane fuel cell applications. Journal of the Electrochemical Society 1992 139 761-765. 

The perfluorosulfonic acid (Nafion) membrane found its application in fuel cells long before its introduction to the chlor-alkali industry (26-28). The Nafion membrane is used as the solid polymer electrolyte (separator/electrolyte) in fuel cells. Figure 2 shows the schematic of such an SPE fuel cell. 

Polymer electrolyte fuel cells, also sometimes called SPEFC (solid polymer electrolyte fuel cells) or PEMFC (polymer electrolyte membrane fuel cell) use a proton exchange membrane as the electrolyte. PEEC are low-temperature fuel cells, generally operating between 40 and 90 °C and therefore need noble metal electrocatalysts (platinum or platinum alloys on anode and cathode). Characteristics of PEEC are the high power density and fast dynamics. A prominent application area is therefore the power train of automobiles, where quick start-up is required. 

Al-air fuel cells, Zn-Mn02 and Al-Mn02 cells, were assembled with anodes, cathodes and alkaline solid polymer electrolyte membranes. The electrochemical cells showed excellent cell power density and high electrode utilization. Therefore, these PVA-based solid polymer electrolyte membranes have great advantages in the applications for all-solid-state alkaline fuel cells. Some other potential applications include small electrochemical devices, such as supercapacitors and 3C electronic products. 

The high temperature electrolytes are mostly oxides of composition MO based upon the fluorite, structure. The best investigated is "calcia stabilized zirconia (CSZ) which consists of a solid solution of 12-15% CaO in ZrO. The addition of calcia transforms ZrO from the monoclinic to tne cubic (fluorite) structure and also introduces anion vacancies for charge compensation. Conduction is by 0 ion diffusion through anion vacancies and ZrO -CaO has a resistivity of 30 ohm-cm at 950 C. Trivalent cations may also be used to stabilise ZrO with resistivities at 950 C of 12 ohm-cm for ZrO -Y 0 and - 6 ohm-cm for ZrO -Yb O or ZrO -Sc O (Figure l). Staoilized zirconia is of interest as an electrolyte for fuel cells, but no battery applications have been proposed and the temperature of conduction is too high to be of real interest. 

Xie D, Jiang YD, Pan W, Li D, Wu ZM, Li YR (2002) Fabrication and characterization of polyanUine-based gas sensor by ultra-thin film technology. Sens Actuators B 81 158-164 Yasuda A, Doi K, Yamaga N, Fujioka T, Kusanagi S (1992) Mechanism of the sensitivity of the planar CO sensor and its dependency on humidity. J Electrochem Soc 139 3224-3229 Zawodzinski TA, Springer TE, Uribe F, Gottesfeld S (1993) Characterization of polymer electrolytes for fuel cell applications. Solid State Ionics 60 199-211... 

PEM stands for polymer electrolyte membrane or proton exchange membrane. Sometimes, they are also called polymer membrane fuel cells, or just membrane fuel cells. In the early days (1960s) they were known as solid polymer electrolyte (SPE) fuel cells. This technology has drawn the most attention because of its simplicity, viability, quick startup, and the fact that it has been demonstrated in almost a conceivable application [1],... 

Zawodzinski TA, Springer TE, Uribe F, Gottesfeld S. Characterization of polymer electrolytes for fuel cell applications. Solid State Ionics 1993 60(1-3) 199-211. 

Electrolysis of water has been used for over a century to produce hydrogen and oxygen. The concept of a reversible fuel cell for space applications is based on a combined electrolytic-galvanic fuel cell. Like fuel cells, several different types of electrolyzers and catalysts have been developed, including atmospheric and high-pressure acid-based polymer electrolyzers, alkaline solution systems, and solid oxide-based systems. 

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