Capacity of double electric layer of IB metal electrodes in alkali halogenide melts

E.V. Kirillova, V.P. Stepanov

KEYWORDS:

capacitance, electric double layer; specific adsorption; molten salts

ABSTRACT:

The capacitance-potential curve shape of metal Au, Ag and Cu electrodes was investigated in 9 molten salts: sodium, potassium and cesium chlorides, bromides and iodides. On Au, The dependence curve of the potential capacitance has an additional minimum at the anodic branch.On Ag, the same minimum is less defined and can be seen only at low AC frequencies and only in cesium halogenides. On Cu, the additional minimum is not observed in all salts studied in this work. The larger cation and/or anion radii shift cathodic and anodic minima towards each other. The electrode metal (M=Au, Ag or Cu) and adsorbed halogenide (X=Cl, Br or I) mechanism of specific adsorption is discussed; forming [MX2]− complexes is suggested to be the reason for surface recharge in the polarization area positive to the potential of zero charge. Reduction and total disappearance of the observed anodic minimum for silver and copper is explained by less bond strength of these complexes.