Perovskite Oxyfluoride Ceramic with In Situ Exsolved Ni–Fe Nanoparticles for Direct CO₂ Electrolysis in Solid Oxide Electrolysis Cells

Abstract

Solid oxide electrolysis cell (SOEC) is a potential technique to efficiently convert CO2 greenhouse gas into valuable fuels. Thus, there is significant interest in developing highly active and stable electrocatalysts for the CO2 reduction reaction (CO2RR). Herein, a Ni and F co-doping strategy is proposed to facilitate the exsolution reaction and form a new cathode, Ni–Fe alloy nanoparticles embedded in ceramic Sr2Fe1.5Mo0.5O6−δ (SFM) doped with fluorine. F-doping and Ni–Fe exsolution enhance CO2 adsorption by a factor of 2.4 and increase the surface reaction rate constant (kchem) for CO2RR from 6.79 × 10–5 to 18.1 × 10–5 cm s–1, as well as the oxygen chemical bulk diffusion coefficient (Dchem) from 9.42 × 10–6 to 19.1 × 10–6 cm2 s–1 at 800 °C. Meanwhile, the interfacial polarization resistance (Rp) decreases by 52%, from 0.64 to 0.31 Ω cm2. At 800 °C and 1.5 V, an extremely high current density of 2.66 A cm–2 and a stability test over 140 h are achieved for direct CO2 electrolysis in the SOEC.