Oxygen Evolution Behavior of La1−xSrxFeO3−δ Electrodes in LiCl−KCl Melt

Abstract

Electrochemical reduction processes of oxides in molten salt have been proposed as the carbon free technology in order to achieve carbon neutral. The anodic behavior of La1−xSrxFeO3−δ as an oxygen-evolution anode in LiCl−KCl at 723 K is investigated. Data suggests that at 723 K, the electrical conductivity of La1−xSrxFeO3−δ tends to increase as the extent of Sr doping. The anodic reactions of La1−xSrxFeO3−δ electrodes are characterized by electrochemical measurements in LiCl−KCl + Li2O at 723 K. Based on the cyclic voltammograms of the La0.7Sr0.3FeO3−δ electrode, oxygen evolution has proceeded between 2.7 V and 3.6 V. The potential of La0.7Sr0.3FeO3−δ electrode during galvanostatic electrolysis has conducted at 39 mA cm-2 for 15 h has remained stable at 2.8 V, indicating that the stable evolution of oxygen gas is monitored. The corrosion rate is estimated to have the low value of 8.6 × 10−4 g cm−2 h−1. Electrode surface data collect after electrolysis indicate that La0.7Sr0.3FeO3−δ electrode has excellent chemical and physical stability in LiCl−KCl at 723 K. Evidence thus indicates that La0.7Sr0.3FeO3−δ electrode is a promising candidate material as inert anodes for oxides decomposition. As one of application of the La0.7Sr0.3FeO3−δ electrode, the electrolysis reduction of CO2 was also successfully achieved.

Relationship between the Thermodynamic Quantities and Coordination Structure of Oxide Ions in CaCl2-Based Chloride Melts

“…The working electrode was La 0.7 Sr 0.3 FeO 3−δ prepared by the method described in our previous report. 12 The reference electrode was an Ag wire immersed in each melt containing 1.0 mol % AgCl in an alumina tube with a thin bottom. The potential of the electrode was calibrated with reference to that of Na(I) and Ca(II)/Na–Ca alloy for the NaCl–CaCl 2 melt, the Na(I), K(I), and Ca(II)/Na–K–Ca alloy for the NaCl–KCl–CaCl 2 melt, and Li(I) and Ca(II)/Li–Ca alloy for the LiCl–KCl–CaCl 2 melt, which was prepared by electrodepositing each alloy on a nickel wire in each melt.…”

“… 11 Because most CaCl 2 -based chloride melts have a high melting point of over 773 K, we used a La 0.7 Sr 0.3 FeO 3−δ electrode, which has high corrosion resistance and high chemical stability against O 2 gas and oxide ions in molten chloride melts at 773 K or higher. 12 …”