Ni–Fe bimetallic cathodes for intermediate temperature CO2 electrolyzers using a La0.9Sr0.1Ga0.8Mg0.2O3 electrolyte

Abstract

A solid oxide electrolysis cell for reducing CO₂ to CO was studied using a LaGaO₃-based electrolyte at intermediate temperatures (973–1173 K). Various metals were examined as cathodes for CO₂ reduction, and it was found that Ni shows high activity. However, coke formation was observed during the initial period. Furthermore, we found that the electrolysis current could be greatly improved by adding Fe to Ni, resulting in a current density of 1.84 A cm⁻² at 1.6 V and 1073 K on a Ni–Fe (9 : 1) cathode. SEM observation suggests that improved cathodic activity can be explained by stabilizing Ni fine particles with the addition of Fe. Therefore, diffusion resistance can be decreased by adding Fe to Ni. The formation rate of CO is slightly lower than the consumption rate of CO₂, suggesting coke formation during the initial period. However, stable CO₂ electrolysis can be performed for at least 12 h, and Fe addition is effective for increasing long-term stability of electrolysis.