טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentDmitry Rozen
SubjectCathodic Charge Transfer and Analysis of Unusual Alkaline
and Silver Fe(VI) Compounds
DepartmentDepartment of Chemistry
Supervisors Professor Emeritus Yarnitzky Chaim (Deceased)
Mr. Licht Stuart


Abstract

This study presents the synthesis, and analyses for a variety of alkali Fe (VI) oxide salts. The Ag2FeO4  is of compelling interest, as it is capable not only of 3e- storage as Fe (VI=>III), but also of  an additional reduction of the Ag (I) sites for a total of a 5e- alkaline reduction.

The Infra Red spectra of alkali Fe(VI) salts  and the first IR spectra of Ag2FeO4  are presented and compared to spectra of K2FeO4. Inductively Coupled Plasma spectra indicate that the cesium salt is pure Cs2FeO4, whereas the rubidium and sodium salts consists of mixtures with potassium, having the effective stoichiometric ratio Rb1.7K0.3FeO4 and Na1.1K0.9FeO4. Each of these salts exhibits a higher degree of solid state stability and a low solubility in the electrolytes of the traditional alkaline batteries’ (millimolar in 13.5M KOH).

For Ag2FeO4 the ICP analysis provides evidence of over 99% conversion from potassium to silver salt, although chromite analysis indicates a 13%  Fe(III) impurity in the Ag2FeO4 product. Ag2FeO4 is less stable than the above mentioned Fe(VI) salts. A final value of fall  in purity from 87% to 83% is demonstrating over a period of 1 week at 0 oC, and to 73% at 25oC.

Alkaline Zn anode batteries in AAA and coin type cells configuration, were prepared with these alternative cathodes and discharged at constant load and controlled temperature conditions. Explanations for the observed effects, as well as further steps of cathodic charge transfer improvement for these salts are being proposed.