Cathode materials Iron-based oxides

Since ionic radii and valences of iron and chromium ions are similar to gallium ion, substitution of these cations with gallium ion may result in powders with similar crystal structure and properties to LSGM. Moreover, LaFe03- and LaCr03-based oxides are candidate cathode and anode materials for SOFC, respectively. 

To overcome the stability problem, it is obvious that an alternative approach to material synthesis would be needed. In this respect a recent report suggested that iron oxide encapsulated in meso- and macroporous carbon can be used as anode in Li batteries and reaches a greatly improved reversibility and rate performance. At the same time, a similar structure for a cathode material based on iron and lithium fluoride was synthesized and investigated. It was demonstrated that encapsulation of transition metal-metal fluoride in nanocarbon might be an effective strategy to improve the cycling performance of such a cathode material. ... 

However, reliable information about dependence of the functional properties of complex nickelates on their chemical composition and structure is still absent, while any straightforward and accelerated design of cathode materials is to be based upon reliable (and independent upon their interaction with electrolyte) characterization of the ability of then-surface sites to catalyze the oxygen reduction as well as of oxygen mobility in the bulk. Several lanthanum-nickel-iron mixed oxides with perovskite structure have demonstrated promising performance as cathodes for IT SOFC with traditional YSZ and GDC electrolytes [111-112]. However, studies of the behavior of electrode materials in contact with ATLS electrolytes or that of ATLS-based composites are veiy scarce [113]. 

Other common anode materials for thermal batteries are lithium alloys, such as Li/Al and Li/B, lithium metal in a porous nickel or iron matrix, magnesium and calcium. Alternative cathode constituents include CaCr04 and the oxides of copper, iron or vanadium. Other electrolytes used are binary KBr-LiBr mixtures, ternary LiF-LiCl-LiBr mixtures and, more generally, all lithium halide systems, which are used particularly to prevent electrolyte composition changes and freezing out at high rates when lithium-based anodes are employed. 

Because of their extensive technological applications, the anodic behavior of most of the nonnoble metals has been extensively investigated. Only a brief outline, with emphasis on the role of hydrous oxide material, is given here. The conditions necessary for the production of a thick hydrous oxide film on iron in base (repetitive cycling between -0.50 and 1.25 V at ca. 3.3 V s 1 at 25°C) have been outlined by Burke and Murphy.202 As outlined in Fig. 11, four peaks [with maxima at ca. -0.04, 0.13, 0.30, and 0.55 V (RHE)] were observed with the bare metal on the first anodic sweep, and only two (-0.05 and -0.20 V) on the subsequent cathodic sweep. On repetitive cycling the anodic peak at +0.3 V and the cathodic peak at -0.05 V became greatly enhanced and the presence of an electrochromic effect was noted. Further indication that a dispersed hydrous oxide film was produced under these conditions... 

When a DC potential is applied to a medium containing water and ions, such as soil, acid is generated at the anode and base at the cathode due to the electrolysis of water. The highly acidic environment near the anode could be detrimental to the electroosmosis process if the zeta potential in the soil falls too low or reverses. Two clever approaches are utilized in the Lasagna process to both minimize the acid effect on soil and keep the anode pH between 5 and 7. First, steel plates are used as the anode material to promote iron oxidation as the main anodic reaction instead of water oxidation, which forms acid (H+). Second, the basic pore water accumulated at the cathode (pH > 12) is recycled by gravity back to the anode as makeup water, which is required for continuing the operation of electroosmosis and at the... 

---