Ferrate(VI) synthesis at a boron-doped diamond anode

Abstract

The electrochemical synthesis of ferrate(VI) by the oxidation of iron compounds from alkaline 10 M KOH electrolytes on a boron-doped diamond electrode was examined by cyclic voltammetry between the potentials of the hydrogen evolution reaction and the oxygen evolution reaction. It was shown that the anodic current peak that appeared in iron-free electrolyte at a less positive potential than the potential of the oxygen evolution probably coincides with oxidation of hydrogen in >CH2 groups and C-sp2 graphite impurities with formation of >C=O groups in a C-sp3 diamond structure. Addition of Fe(III) compounds to the electrolyte provoked the formation of an anodic wave on the cyclic voltammograms in the potential region that correlates with the generation of ferrate(VI). It is concluded that the direct electrochemical synthesis of Fe(VI) at a boron-doped diamond anode is possible because of the less positive potential of ferrate(VI), FeO 42-, formation with respect to the potential of the oxygen evolution reaction. The presence of ferrate(VI) in the electrolyte, formed after anodic polarization of the boron electrode in 10 M KOH electrolyte saturated with Fe(III) at 0.9 V against Hg/HgO electrode, was proven by UV-Vis spectrometry.