Electrochemical properties of the Ag +|Ag and other reference electrodes in the LiCl–KCl eutectic melts

Abstract

Thermochemical properties of the Ag +|Ag reference electrode were investigated by comparison with those of the Cl −|Cl 2 reference electrode in the LiCl–KCl eutectic melt at 673–873 K, and the influence of the AgCl concentration on the equilibrium potential was also studied. The potential difference between the Ag +|Ag electrode and the Cl −|Cl 2 reference electrode varied in nearly linear proportion to the concentration of AgCl ranging from 0.01 to 20 mol%. When the AgCl concentration in the inner solution of the Ag +|Ag electrode was 1.02 mol%, the equilibrium potential, E, of the Ag +|Ag electrode versus the Cl −|Cl 2 reference electrode at 673–873 K is described as following: E = −1.061 (±0.005) + 0.0000649 (±0.0000010) T, where T is the temperature in K. Since the density increased with an increase of the AgCl content, the mole number of electrolytes in a given volume increased. Accordingly, the standard redox potential, E A g + | Ag 0 , could be corrected by the equation: E A g + | Ag 0 = − 1.080 ( ± 0.005 ) + 0.000346 ( ± 0.000005 ) T . Furthermore, characteristics of other reference electrodes such as the Al 3+|Al and Li +|Li (Li–Al and Li–Sb alloys) electrodes were investigated. The standard redox potential, E A l 3 + | Al 0 , of the Al 3+|Al couple at 673–873 K is described as following: E A l 3 + | Al 0 = − 2.289 ( ± 0.005 ) + 0.000405 ( ± 0.000005 ) T . The equilibrium potential between the Li–Al (Li:Al = 42:58 in mol%) and the Cl −|Cl 2 reference electrode, E L i + | Li ( Li – Al ) and that between the Li–Sb (Li:Sb = 59:41 in mol%) alloys electrode and the Cl −|Cl 2 reference electrode, E L i + | Li ( Li – Sb ) , were obtained at the temperature range from 673 to 873 K ( E L i + | Li ( Li – Al ) = − 3.923 ( ± 0.005 ) + 0.000860 ( ± 0.000005 ) T and E L i + | Li ( Li – Sb ) = − 2.960 ( ± 0.005 ) + 0.000313 ( ± 0.000005 ) T .