Electrolytic Reduction of CO2 Using Perovskite-Type La-Based Oxide Anodes in Chloride Molten Salts

Abstract

CO2 decomposition in molten salt is an attractive process as a new method for achieving carbon neutrality, for which the development of inert anodes and electrolytic bath suitable for CO2 decomposition is essential. Previous studies mostly investigated the electrode material but did not investigate the relationship between the electrolysis bath and electrode reaction. The effects of the electrolytic bath on anode reaction and the development of inert anode material with high current density were investigated in this study. Electrolytic bath of LiCl–CaCl2 and NaCl–CaCl2 with similar oxide solubilities were compared, finding that LiCl–CaCl2 melts exhibited higher oxidation current density in cyclic voltammetry and more stable potential transition in galvanostatic electrolysis. Among the five anodes with a perovskite-type La-based oxide were investigated, La0.6Sr0.4CoO3−δ showed the highest electrical conductivity and the largest increase in oxidation current density. CO2 decomposition tests were performed in LiCl–CaCl2 with CaO and CaCO3 added as a CO2 source at 873 K using La0.6Sr0.4CoO3−δ anode. Only C and O2 were recovered from CO2 by electrolysis test. The current efficiencies were 78.3% and 54.4%, respectively. The La0.6Sr0.4CoO3−δ anode exhibited excellent corrosion resistance, demonstrating its potential as a promising inert anode for CO2 decomposition.