Solid Oxide Electrolyte SOE

Current Voltage Ely Voltage FC Efficiency Ely Efficiency FC Efficiency 

In FC and electrolysis operating modes, the performance of the oxygen electrode decreases in the order lanthanum strontium cobalt ferrites (LSCFs) lanthanum strontium ferrites (LSFs) lanthanum strontium manganites (LSMs). The degradation stability of LSCFs and LSFs in electrolysis mode is better than that of LSMs and YSZ. 

The materials used for hydrogen electrodes are Ni- and Cu-based or conducting ceramic electrodes. Owing to possible polarization losses for hydrogen electrodes in electrolysis mode (different diffusion behaviors of H2 and H2O), thinner electrodes and smaller particles are preferred [78]. Typical performance data for an SOE URFC are given in Table 8.10. 

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Fig. 2.5 A solid oxide electrolyte (SOE) electrolyzer configuration (planar geometry).

Fundamental research in the field of SOFCs started in Russia in the end of 1950s at the Institute of Electrochemistry in Sverdlovsk (now the Institute of High Temperature Electrochemistry, IHTE, Ekaterinburg). From the very outset, the works included study of solid oxide electrolytes (SOEs), electrode materials and electrode kinetics, other components of SOFC interconnects, seals, etc. 

Different technologies can be used for RFC systems. Electrolyzers can be classified by the electrolyte they use alkaline, polymer electrolyte membrane (PEM) and solid oxide electrolyte (SOE) [5]. Alkaline, PEM, and SOE electrolyzers can also be used for FCs. The electrolytes differ according to the ion that is conducted and their operating temperatures (Table 8.1). 

Complex FCC oxides of the fluorite type represent oxygen-conduction solid electrolytes (SOE s). They comprise a typical class of materials for the manufacture of sensors of oxygen activity in complex gas mixtures, oxygen pumps, electrolyzers and high-temperature fuel elements. These materials are based on doped oxides of cerium and thorium, zirconium and hafnium, and bismuth oxide. Materials based on zirconium oxide, for example, yttrium stabilized zirconia (YSZ) are the most known and studied among them. This fact is explained both by their processibility and a wide spectrum of practical applications and by the possibility to conduct studies on single crystals, which have the commercial name "fianites" and are used in jewelry. 

In the literature, the acronyms SOEC (Solid Oxide Electrolyzer Cell) or SOE also occur fairly regularly. The term high-temperature electrolysis (HTE) is fairly common, referring to the operating temperature of the component (typically 800°C) rather than to the nature of its electrolyte. 

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