Perovskite-type cathodes

Poor ionic conductor, incompatible with perovskite-type cathode materials (e.g., Sr-doped LaM03 (M = Mn, Co) at elevated temperatures and long period of operation time... 

Later (Hwang et al., 2001 Matsuda et al., 2001 Washman et al., 2000) a series Lai-j A BOs perovskite were prepared and systematically evaluated for substitution of the Ft or Pd electrodes. A major target of all these researches was the promotion of NO reduction by F -center type defects in the YSZ surface or inside perovskite type cathodes (Hwang et al., 2001 ... 

An example for a compound of the perovskite type is LaNiOj. In other com-ponnds of the perovskite type, nickel may be replaced by cobalt or iron, and lan-thannm in part by alkaline-earth metals, an example being Lag 8Sro2Co03. The activity of perovskites toward cathodic oxygen reduction is low at room temperature but rises drastically with increasing temperature (particularly so above 150°C). In certain cases the activity rises so much that the equilibrium potential of the oxygen electrode is established. 

Perovskite-type oxides are well known oxidation catalysts in the gas phase [259]. In 1970, Meadowcroft suggested that LaCo03 doped with strontium was a less expensive alternative to platinum for air cathodes in alk-... 

Other developments of perovskite-type oxides as cathode materials for fiiel cells have been discussed in detail in the reviews by Skinner and Brandon. ... 

To solve the problems associated with the instability of state-of-the-art NiO cathodes, research has been focused on the development of new stable cathode materials to replace NiO. Currently, perovskite types of compounds and mixed metal oxides such as LiFe02 and LiCo02 have been evaluated as cathode materials. " ... 

III. ACTIVATION OF MIXED-CONDUCTING PEROVSKITE-TYPE OXIDE CATHODES... 

An example of the use of nanoionic materials as the cathode in a SOFC is that of nanotubes of Lao.6Sro.4Co03 and Lao.6Sro.4Coo.2Feo.8O3 [136]. These perovskite-type mixed oxides (see Chapters 9 and 12) are widely used as cathode materials, and the nanotubes were prepared by denitration, microwave irradiation and calcination at 800 °C. The shape and size of the nanotubes was controlled by the porous template used, although their application in a fuel cell was not reported. 

More recently efforts have been directed towards the development of perovskite related cathode materials, particularly those of the K2Nip4 structure type [2,3], Fig. 1. These oxides consist of alternating layers of ABO3 and AO (rock salt) and have been demonstrated to accommodate a significant oxygen non-stoichiometry. 

The ORR was also analyzed on perovskite-type oxide Laj xStx Mn03 in direct ethylene glycol alkaline fuel cells (DEGAFQ observing a high tolerance to EG since the cathodic polarization curves were not affected by the concentration of EG supplied to the anodic side [57]. 

Miyazaki K, Sugimura N, Matsuoka K, Iriyama Y, Abe T, Matsuoka M, Ogumi Z (2008) Perovskite-type oxides Lai xSrxMn03 for cathode catalysts in direct ethylene glycol alkaline fuel cells. J Power Sources 178 683-686... 

In addition to the LSM-type cathode cells, LSC(F)-type cells have also been developed and improved. Cells with an LSC(F)-type cathode can be used at temperatures lower than 750 °C, in contrast to the LSM-type cathode cells, which perform best above 750 °C. The decrease in the power density at lower temperatures, in particular for cells with an LSM cathode, is mainly due to overpotentials at the cathode side. Therefore, research was focused on new cathode materials with higher electrocatalytic activity than the state-of-the-art LSM perovskites. As a result, LSC(F) was chosen as the material for operating temperatures lower than 800 °C, since it possesses high electronic and ionic conductivity, which make this material an excellent candidate as an MI EC (mixed ionic and electronic conductive) cathode. 

Skinner, S.J. (2001). Recent Advances in Perovskite-type Materials for Solid Oxide Fuel Cell Cathodes. International Journal of Inorganic Materials, Vol. 3, (March 2001), pp. 113-121, ISSN 1466-6049... 

As the anion-exchange membrane fuel cell is the alkaline-based system, we can use non-platinum-based catalyst. This is a big advantage to lower the cost of fuel cells. Especially perovskite-type and pyrochlore-type oxides have high performance to oxygen-electrocatalysts which could be applicable to the cathode materials. Some oxides have also bifunctional activities as oxygen electrode catalyst to produce a reversible fuel cell thus, future deployment is expected. While, the big problems are stability of the base... 

Miura N, Shimizu Y, Yamazoe N, Seiyama T (1985) Kinetics of cathodic oxygen reduction on lanthanum-based perovskite-type oxides. Nippon Kagaku Kaishi 1985(4) 644... 

SOFC cathodes are typically perovskite-type oxides formed as a composite with a suitable electrolyte (either YSZ for high-temperature operation or CGO for lower operating temperatures) and... 

Ulhnann H, Trofimenko N, Tietz F, Stover D, Ahmad-Khanlou A (2000) Correlation between thermal expansion and oxide ion transport in mixed conducting perovskite-type oxides for SOFC cathodes. Solid State Irai 138 79-90... 

Inoue T, Seki N, Eguchi K, Arai H (1990) Low-temperature operation of solid electrolyte oxygtai sensors using perovskite-type oxide electrodes and cathodic reaction kinetics. J Electrochem Soc 137(8) 2523-2527... 

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