Ni-Fe-La(Sr)Fe(Mn)O₃ as a new active cermet cathode for intermediate-temperature CO₂ electrolysis using a LaGaO₃-based electrolyte

Various additives to Ni-Fe systems are studied as cermet cathodes for CO₂ electrolysis (973-1173 K) using a La_0.9Sr_0.1Ga_0.8Mg_0.2O₃ (LSGM) electrolyte, which is one of the most promising oxide-ion conductors for intermediate-temperature solid-oxide electrolysis cells in terms of ionic-transport number and conductivity. It is found that Ni-Fe-La_0.6Sr_0.4Fe_0.8Mn_0.2O₃ (Ni-Fe-LSFM) exhibits a remarkable performance with a current density of 2.32 A cm^-2 at 1.6 V and 1073 K. The cathodic overpotential is significantly decreased by mixing the LSFM powder with Ni-Fe, which is related to the increase in the number of reaction sites for CO₂ reduction. For Ni-Fe-LSFM, much smaller particles (<200 nm) are sustained under CO₂ electrolysis conditions at high temperatures than for Ni-Fe. X-ray diffraction analysis suggests that the main phases of Ni-Fe-LSFM are Ni and LaFeO₃; thus, the oxide phase of LaFeO₃ is also maintained during CO₂ electrolysis. Analysis of the gaseous products indicates that only CO is formed, and the rate of CO formation agrees well with that of a four-electron reduction process, suggesting that the reduction of CO₂ to CO proceeds selectively. It is also confirmed that almost no coke is deposited on the Ni-Fe-LSFM cathode after CO₂ electrolysis.