Highly active oxide cathode of La(Sr)Fe(Mn)O3 for intermediate temperature CO2 and CO2-H2O co-electrolysis using LSGM electrolyte

Abstract

Electrochemical conversion of carbon dioxide to carbon monoxide (CO2→CO) is a potential step in the desirable transformation of the greenhouse gas to fuel or useful chemicals. In this study, the electrochemical conversion of CO2 to CO and H2O to H2 on an oxide cathode was studied in a solid oxide electrolysis cell (SOEC) by using a LaGaO3-based electrolyte (La0.9Sr0.1Ga0.8Mg0.2O3, LSGM) at elevated temperature (i.e. 973–1173K), which is a good candidate as electrolyte for electrolysis cell because of the high oxide ion conductivity at intermediate temperatures. Although metal, in particular, Ni is widely used as cathode of CO2 electrolysis cell, it was found that a LaFeO3−δ–based perovskite material as cathode (La0.6Sr0.4Fe0.8Mn0.2O3−δ, LSFM6482) shows much higher activity and selectivity to CO2 electrolysis and a current density of CO2 electrolysis is achieved with a value of 0.52A/cm2 at 1.6V and 1173K. In contrast, substitution of Co, Cu, and Ni decrease the anodic performance of LaFeO3 resulting in the decrease in electrolysis current. A cell using the LSFM6482 oxide cathode has a high selectivity for the electrolysis of CO2 to CO without carbon formation. In this study, application of LSGM6482 to CO2-H2O co-electrolysis was also studied and it was found that CO2-H2O co-electrolysis was successfully proceeded and CO/H2 syngas with ca. 1/1 ratio was obtained from CO2/H2O=1/1.