Yuya Kado

Electrochemical Behavior of Oxide Ion in a LiCl – NaCl – CaCl2 Eutectic Melt

The solubility of lithium oxide was determined to be 5.2 mol % in a LiCl-NaCl-CaCl 2 eutectic melt (52.3:13.5:34.2 mol %, melting point 713 K) at 773 K. The electrochemical window of the melt, 3.4 V, was determined by cyclic voltammetry at 773 K. The reaction at the anode limit was confirmed as Cl 2 gas evolution. The reaction at the cathode limit was found to be a liquid Li-Na-Ca alloy formation identified by X-ray photoelectron spectroscopy and inductively coupled plasma analyses of the deposits. Oxygen gas evolution occurred without dissolution of anode material according to the reaction, O 2- → 1/2O 2 + 2e - , when a boron-doped diamond electrode was anodically polarized at more positive potentials than 3.0 V vs Li + , Na + , Ca 2+ /Li-Na-Ca in a LiCl-NaCl-CaCl 2 melt containing Li 2 O at 773 K.

Oxygen Electrode Reaction in a LiCl–KCl Eutectic Melt

Oxygen electrode reaction was investigated on a boron-doped diamond electrode in a LiCl―KCl eutectic melt. The standard formal potential of O 2 /O 2― decreases with the elevation of temperature. The potential at 773 K is 2.424 ± 0.003 V vs Li + /Li. The standard formal free energy change increases with the temperature elevation, calculated to be ―456.4 ± 0.5 kJ mol ―1 at 773 K. The standard formal entropy and enthalpy changes are determined to be ―151 ± 3 J K ―1 mol ―1 and ―573.5 ± 0.1 kJ mol ―1 , respectively, at 773 K.

Behavior of a Boron-Doped Diamond Electrode in Molten Chlorides Containing Oxide Ion

Behavior of a boron-doped diamond electrode as an oxygen evolution electrode material was investigated at 773 K in molten LiCl–KCl (58.5:41.5 mol%), LiCl–KCl (75:25 mol%), LiCl–CaCl2 (64:36 mol%), LiCl–NaCl–CaCl2 (52.3:13.5:34.2 mol%) containing oxide ion. In molten LiCl–KCl systems, the BDD electrode is stable and its stability does not depend on the concentration of oxide ion and the melt composition. In molten LiCl–CaCl2 and LiCl–NaCl–CaCl2, the BDD electrode is less stable than in molten LiCl–KCl systems.