Active Cu and Fe Nanoparticles Codecorated Ruddlesden–Popper-Type Perovskite as Solid Oxide Electrolysis Cells Cathode for CO2 Splitting

Solid oxide electrolysis cells (SOECs), displaying high current density and energy efficiency, have been proven to be an effective technique to electrochemically reduce CO₂ into CO. However, the insufficiency of cathode activity and stability is a tricky problem to be addressed for SOECs. Hence, it is urgent to develop suitable cathode materials with excellent catalytic activity and stability for further practical application of SOECs. Herein, a reduced perovskite oxide, Pr_0.35Sr_0.6Fe_0.7Cu_0.2Mo_0.1O_3-δ (PSFCM0.35), is developed as SOECs cathode to electrolyze CO₂. After reduction in 10% H₂/Ar, Cu and Fe nanoparticles are exsolved from the PSFCM0.35 lattice, resulting in a phase transformation from cubic perovskite to Ruddlesden–Popper (RP) perovskite with more oxygen vacancies. The exsolved metal nanoparticles are tightly attached to the perovskite substrate and afford more active sites to accelerate CO₂ adsorption and dissociation on the cathode surface. The significantly strengthened CO₂ adsorption capacity obtained after reduction is demonstrated by in situ Fourier transform-infrared (FT-IR) spectra. Symmetric cells with the reduced PSFCM0.35 (R-PSFCM0.35) electrode exhibit a low polarization resistance of 0.43 Ω cm² at 850 °C. Single electrolysis cells with the R-PSFCM0.35 cathode display an outstanding current density of 2947 mA cm⁻² at 850 °C and 1.6 V. In addition, the catalytic stability of the R-PSFCM0.35 cathode is also proved by operating at 800 °C with an applied constant current density of 600 mA cm⁻² for 100 h.