טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentHalperin Leonid
SubjectPreparation and Analysis of Stabilized Fe(VI) Compounds
DepartmentDepartment of Chemistry
Supervisors Professor Emeritus Chaim Yarnitzky (Deceased)
Mr. Stuart Licht


Abstract


Alkali permanganates represent a substantial cathodic charge source for electrochemical storage, but high rate charge transfer has been inefficient. This study presents a novel Fe(VI) species (super-iron) and manganese redox chemistry synergism. The characterization and optimization of the syntheses of BaFeO4 and K2FeO4 are also presented in the following study. Fe(VI) compounds have also been variously referred to as ferrates and include K2FeO4 and BaFeO4.

The discharge efficiency of solid alkaline permanganate cathodes is probed and the improved charge transfer of Mn(VII) redox chemistry in the presence of Fe(VI) is demonstrated. The high discharge energies from cathodes which utilize the phenomenon of super-iron/manganese charge transfer synergism in a conventional cylindrical battery configuration are probed and exhibit an unusually high discharge capacity of 2.2 Wh.

The chemistry optimizing the preparation of high purity potassium and barium ferrates for alkaline electrochemical storage is presented. The first long term, solid state stability of an Fe(VI) salt is demonstrated with results of five hundred days. These synthesized Fe(VI) products are shown to provide an energetic cathodic discharge in alkaline electrochemical storage cells using a Zn anode in an AAA cell configuration.

Chemical and electrochemical techniques are presented for the analysis of Fe(VI) compounds used in super-iron electrochemical storage cells. The investigated FTIR methodology becomes quantitative with the introduction of an internal standard such as added barium sulfate. The titrimetric methodology (chromite analysis) has been detailed and methodologies modified to determine the extent of the Fe(VI→III) oxidation power in both unmodified or coated Fe(VI) compounds.