Ferrate(VI) synthesis at boron-doped diamond anode

The oxidation of iron compounds from alkaline 10 M KOH electrolytes on a boron doped diamond electrode is examined by cyclic voltammetry between the potentials of hydrogen evolution reaction and oxygen evolution reaction, due to ferrate(VI) electrochemical synthesis. It is shown that the anodic current peak that appears in iron free electrolyte at a less positive potential than the potential of oxygen evolution probably coincides with oxidation of hydrogen in >CH2 groups and C-sp2 graphite impurities with formation of >C=O groups at C-sp3 diamond structure. Addition of Fe(III) compounds to the electrolyte provoke formation of the anodic wave on cyclic voltammograms in the potential region which correlates with generation of ferrate(VI). It is concluded that the direct electrochemical synthesis of Fe(VI) at the boron doped diamond anode is possible because of the less positive potential of ferrate(VI)FeO2-4 formation in respect to the potential of oxygen evolution reaction. Presence of ferrate(VI) in electrolyte, formed after anodic polarization of boron electrode in 10 M KOH electrolyte saturated with Fe(III) at + 0.9 V against Hg|HgO electrode, has been proven by UV-VIS spectrometry.