Analysis of ferrate(VI) compounds and super-iron Fe(VI) battery cathodes: FTIR, ICP, titrimetric, XRD, UV/VIS, and electrochemical characterization

Chemical and electrochemical techniques are presented for the analysis of Fe(VI) compounds used in super-iron electrochemical storage cells. Fe(VI) analytical methodologies summarized are FTIR, ICP, titrimetric, UV/VIS, XRD Fe(VI), potentiometric, galvanostatic, cyclic voltammetry, and constant load, current or power electrochemical discharges probes. The investigated FTIR methodology becomes quantitative with introduction of an internal standard such as added barium sulfate. Electrochemical techniques which utilize a solid cathode, and spectroscopic techniques which utilize a solid sample, are preferred over solution phase techniques. The titrimetric methodology (chromite analysis) has been detailed, and adjusted to determine the extent of Fe(VI→III) oxidation power in both unmodified or coated Fe(VI) compounds. Fe(VI) compounds have also been variously referred to as ferrates or super-iron compounds, and include K2FeO4 and BaFeO4. Such compounds are highly oxidizing, and in the aqueous phase the full three electron cathodic charge capacity has been realized, as summarized by reactions such as: FeO42−+5/2H2O+3e−→1/2Fe2O3+5OH−.