A nanoparticle-decorated bismuth- and nickel-doped Sr2Fe1.5Mo0.5O6−δ cathode for enhanced CO2 reduction in solid oxide electrolysis cells

Abstract

Solid oxide electrolysis cells (SOECs) are a promising technology for CO₂ electrolysis and subsequent conversion to useful chemicals. This paper presents the development of a new cathode material to enhance the performance of SOECs for CO₂ electrolysis. The focus was on the cathode material of the SOEC since it is the limiting factor for CO₂ electrolysis. Sr₂Fe_1.5Mo_0.5O_6−δ (SFM) has attracted much attention due to its decent performance for CO₂ electrolysis. To enhance the SFM performance, it was modified by doping bismuth and nickel to make a new composition of Bi_0.1Sr_1.9Fe_1.4Ni_0.1Mo_0.5O_6−δ (BiSFMNi)_. The Ni-doping made it possible for Fe–Ni nanoparticles to exsolve in situ when the material was reduced by 5% H₂/Ar. Structural characterization techniques like XRD showed that, during exsolution, the material changed from a pure double perovskite structure to a mixed-phase material with both Ruddlesden–Popper (RP) and residual double perovskite phases and metallic nanoparticles. Electron microscopy (SEM/TEM/EDS) showed that Ni migrated to the surface of the perovskite bulk where it forms Fe–Ni nanoparticles. This material was then used as the cathode of SOECs, and the results showed that these exsolved Fe–Ni nanoparticles improved the electrocatalytic activity of the CO₂ reduction reaction (CO₂RR). The fabricated cell achieved a current density of 1.3 A cm⁻² at 800 °C under an applied voltage of 1.6 V, while it was 1.0 A cm⁻² for the non-exsolved nanoparticle sample.