Enhancing puncture voltage of La0.8Sr0.2Ga0.8Mg0.2O3-δ solid electrolyte membrane by improving CO2 reduction kinetics

Abstract

Solid oxide electrolyte membrane is the core component of solid oxide cells and determines the efficiency of energy conversion. Identifying the failure mechanism of electrolyte membrane and the corresponding strategy to sustain its function at high voltages are significant to promote the development of solid oxide electrolysis cells (SOECs). In this study, we thermodynamically predict that the Ga–O bond of octahedral GaO6 in La0.8Sr0.2Ga0.8Mg0.2O3-δ (LSGM22) electrolyte membrane is prone to be electro-reduced during the electro-driven CO2 reduction reaction (CO2RR). Our experimental results verify that the LSGM22 electrolyte membrane is electro-reduced at 1.4 V and 800 °C, decomposing into LaSrGaO4, La2O3, SrO, MgO and Ga. The inadequate supply of oxygen ions flux, due to the sluggish kinetics of CO2RR, is the inducing factor for the functional failure of LSGM22 electrolyte membrane. Therefore, applying a highly active cathode is proposed to increase the puncture voltage via facilitating CO2RR kinetics and avoiding the reduction of Ga–O bond. La0.5Sr0.5FeO3-δ is employed as an example to show the validity of this strategy, and improves the puncture voltage from 1.4 to 1.6 V.