(707d) Exsolution of Nife Nanoparticles on Ni-Doped (La,Sr)FeO3: Its Effect on Co-Electrolysis of CO2 and H2o for Syngas Production

A promising strategy to reduce the atmospheric CO₂ levels is the conversion of CO₂ into valuable chemicals or fuels. Nowadays the electrocatalytic conversion of CO₂ has received significant attention due to the fact that the high-temperature electrolysis of CO₂ and co-electrolysis of CO₂ and H₂O for syngas production processes offer higher conversion and enhanced reaction kinetics since the system can be operated at elevated temperatures.

In this study, A-site deficient, strontium and nickel doped lanthanum ferrite perovskite oxide (LSNF) was synthesized as a SOEC cathode material. LSNF perovskite has demonstrated the exsolution of NiFe nanoparticles and structural transformation to Ruddlesden-Popper (RP) phase under a reducing environment at 500–800 ^oC, as determined by different methods of characterization such as TPR, ETEM and in-situ XRD. The XRD patterns showed that Red-LSNF was composed of hetero-phases including La₂NiO₄, La₂O₃ and the exsolved nanoparticles, which formed a uniform size distribution (4.2–9.2 nm) and dispersion (1.31–0.61x10⁴ particle μm^–2). Additionally, it has been found that the exsolution process is reversible in such a way that Red-LSNF is re-oxidized to its original perovskite structure under oxidizing environment. The redox ability of LSNF perovskite allows for re-establishing the nanoparticle distribution as is needed. The electrocatalytic activity results showed that Red-LSNF has significantly higher activity for the co-electrolysis of CO₂ and H₂O due to the presence of reduced oxidation states of B-site ions (proved by XPS and XANES results), better accessibility of the active sites via exsolution of active nanoparticles to the electrode surface, and formation of oxygen vacancies that serve as adsorption sites for CO₂ and H₂O. The reduction of LSNF ultimately improved the electrochemical performance by 66–73% on ASRs for H₂O, CO₂, and H₂O/CO₂ electrolysis at 800 ^oC.