A robust fluorine-containing ceramic cathode for direct CO2 electrolysis in solid oxide electrolysis cells

Abstract

Strontium-doped lanthanum ferrite (LSF) is a potential ceramic cathode for direct CO2 electrolysis in solid oxide electrolysis cells (SOECs), but its application is limited by insufficient catalytic activity and stability in CO2-containing atmospheres. Herein, a novel strategy is proposed to enhance the electrolytic performance as well as chemical stability, achieved by doping F into the O-site of the perovskite LSF. Doping F does not change the phase structure but reduces the cell volume and improves the chemical stability in a CO2-rich atmosphere. Importantly, F doping favors oxygen vacancy formation, increases oxygen vacancy concentration, and enhances the CO2 adsorption capability. Meanwhile, doping with F greatly improves the kinetics of the CO2 reduction reaction. For example, kchem increases by 78% from 3.49 × 10−4 cm s−1 to 6.24 × 10−4 cm s−1, and Dchem doubles from 4.68 × 10−5 cm2 s−1 to 9.45 × 10−5 cm2 s−1. Consequently, doping F significantly increases the electrochemical performance, such as reducing Rp by 52.2% from 0.226 Ω cm2 to 0.108 Ω cm2 at 800 °C. As a result, the single cell with the F-containing cathode exhibits an extremely high current density of 2.58 A cm−2 at 800 °C and 1.5 V, as well as excellent durability over 200 h for direct CO2 electrolysis in SOECs.