High La/Sr ratio in La0.67Sr0.33Fe0.67Ti0.33O3-δ cathode induced a controlled Fe0 exsolution for CO2 electrolysis

This study aimed at improving electrocatalytic activity of solid oxide electrolysis cell (SOEC) cathode via in-situ exsolved nanoparticles. La0.67Sr0.33Fe0.67Ti0.33O3-δ (LSFT) and La0.67Sr0.33Fe0.6Ni0.067Ti0.33O3-δ (LSFNT-67) cathodes with a La/Sr ratio about 2.0 showed the exsolution of Fe0 and FeNi3 alloy nanoparticles, respectively, under a reducing atmosphere. The SOEC with LSFT of electrocatalysis is better than LSFNT-67 at 800 °C for direct electrolysis of CO2, the current density of LSFT and LSFNT-67 reach − 0.54 A cm−2 and − 0.29 A cm−2, respectively, and the Faradaic efficiency is close to unity during the 25 h′ durability under a − 1.3 V bias. The better cell performance for the cell with LSFT than LSFNT-67 could be related to the larger distortion and the less amount of insulating LaSrGa3O7 in the former, causing its unexpectedly larger quantity of metal exsolution and electron conduction for more active reaction sites for CO2 activation. This work demonstrated that apart from thermodynamic consideration, steric effect of the B site cation could be important for the exsolution of metal particles from a perovskite with high La/Sr ratio and the resultant electrocatalysis of CO2 electrolysis.