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 Sr₂Fe_1.5Mo_0.5O_6-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 (<i>k</i>_chem) for CO₂RR from 6.79 × 10^-5 to 18.1 × 10^-5 cm s^-1, as well as the oxygen chemical bulk diffusion coefficient (<i>D</i>_chem) from 9.42 × 10^-6 to 19.1 × 10^-6 cm² s^-1 at 800 °C. Meanwhile, the interfacial polarization resistance (<i>R</i>_p) 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.