La_0.6Sr_0.4Fe_0.8Ni_0.2O_3-δ perovskite with in-situ exsolved Ni-Fe nanoparticles as high activity catalyst for symmetric solid oxide electrolysis cells

Effective electrode materials play a key role to enhance electrochemical performances of symmetric solid oxide electrolysis cells (SSOECs). Herein, “exsolution effect” of perovskite oxide at high temperature and reducing atmosphere is introduced. As a proof, La_0.6Sr_0.4Fe_0.8Ni_0.2O_3-δ(LSFN) perovskite decorated with in-situ exsolved Ni-Fe alloy nanoparticles is reported as electrode materials of SSOECs. XRD, SEM, TEM, and XPS characterizations prove the formation of Ni-Fe alloy. The as-prepared SSOECs deliver improved electrochemical performances for both steam electrolysis (50%H₂O/50%H₂) and co-electrolysis (50%H₂O/40%CO₂/10%H₂), current densities of 0.64 and 0.67 A⋅cm⁻² are obtained at 1.3 V and 800^◦C, respectively. Electrochemical impedance spectroscopy (EIS) and distribution of relaxation time (DRT) analysis show that the in-situ formed Ni-Fe nanoparticles can provide a new reaction path for water/hydrogen half-reaction, and electrochemical activity and kinetics of oxygen evolution reaction (OER) can be significantly enhanced by RP type perovskite oxide after reoxidation treatment. Moreover, the SSOECs successfully runs for 60 h at 1.2 V without obvious performance degradation.