Electrocatalysis with solid electrolyte cells

In general, losses due to polarization are less in high-temperature fuel cells than in low-temperature cells. Satisfactory electrocatalysis is a minor problem. Corrosion in the liquid phase has to be overcome in fuel cells with aqueous electrolytes and carbonate electrolytes while corrosion of the electrocatalyst in the gaseous phase of the fuels is one of the major problems of the fuel cells with solid electrolyte. 

Solid-state electrochemistry — is traditionally seen as that branch of electrochemistry which concerns (a) the -> charge transport processes in -> solid electrolytes, and (b) the electrode processes in - insertion electrodes (see also -> insertion electrochemistry). More recently, also any other electrochemical reactions of solid compounds and materials are considered as part of solid state electrochemistry. Solid-state electrochemical systems are of great importance in many fields of science and technology including -> batteries, - fuel cells, - electrocatalysis, -> photoelectrochemistry, - sensors, and - corrosion. There are many different experimental approaches and types of applicable compounds. In general, solid-state electrochemical studies can be performed on thin solid films (- surface-modified electrodes), microparticles (-> voltammetry of immobilized microparticles), and even with millimeter-size bulk materials immobilized on electrode surfaces or investigated with use of ultramicroelectrodes. The actual measurements can be performed with liquid or solid electrolytes. 

The desirability of constructing a fuel cell with a solid electrolyte that is stable during the time of operation was already recognized by Haber [1], Nernst [2], and Baur [3]. Since the problem of electrocatalysis is not serious [4,5] at temperatures around 1000 °C, the main emphasis has been on the improvement of solid electrolytes and on the development of suitable cell designs in recent years. 

Porous metallic structures have been used for electrocatalysis (Chen and Lasia, 1991 Kallenberg et al., 2007). Porous electrodes are made with conductive materials that can degrade under high temperatures at high anodic potential conditions. This last problem is of less importance for fuel cell anodes, which operate at relatively low potentials, but it can be of importance for electrochemical reactors. Porous column electrodes prepared by packing a conductive material (carbon fiber, metal shot) forming a bar are frequently used. Continuous-flow column electrolytic procedures can provide high efficiencies for electrosynthesis or removal of pollutants in industrial situations. Theoretical analysis for the electrodeposition of metals on porous solids has been provided by Masliy et al. (2008). 

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