Electrochemical investigation of the stable chromium species in molten FLINAK

The electrochemical behavior of Cr(III) in FLINAK melts at 600 degrees C was studied through cyclic voltammetry (CV) and square wave voltammetry (SWV). Cr(III) reduction proceeded in two steps: initial Cr(III) reduction to Cr(II) followed by subsequent reduction to Cr. The peak corresponding to the reduction of Cr(III) to Cr(II) was also observed in SWVs and CVs even though only CrF2 was added to the FLINAK melts. This result confirms that Cr(II) was converted to Cr(III) via disproportion: 3Cr(II) = 2Cr(III) + Cr. Such a conversion could be attributed to the formation of the stable species [CrF6](3-), as determined through Raman spectroscopy.