Modification of carbon electrodes by a nitrate-based treatment

Abstract

The modification of raw carbon electrodes by a nitrate-based treatment improves the fluorine evolution process on carbon anodes. In the case of Al(NO3)3-impregnated electrodes, these improvements are attributed to the formation, at the electrode/KF-2HF interface, of a ternary conducting compound Cx(AIF3)yF, i.e. a GIC, instead of insulating graphite fluorides, CFx. In addition, the effect of the NO3 anions of the impregnation solution is demonstrated by impedance spectroscopy, scanning electron microscopy and mercury porosimetry. Impregnation of crude carbon electrodes by nitrate salts, followed by heat treatment, induces smoothing of the electrode surfaces and an increase in the diameter of the pores. This treatment also improves the electronic transfer at the interface and enhances the wet-ability of the electrode by the melt.