Fluorine doped non-perovskite-type Fe2TiO5 oxide without alkaline earth elements as cathode for efficient CO2 electrolysis

Insufficient catalytic activity and stability of the present cathode materials inevitably hamper the industrial applications of solid oxide electrolysis cells (SOECs). Developing efficient cathodes is still a challenging task in the field of SOECs. This paper reports a novel non-perovskite-type cathode material with F doping (Fe2TiO5-δF0.2) and without any alkaline earth elements. F doping increases the surface oxygen vacancies and improves the CO2 adsorption capacity and conductivity of Fe2TiO5. The absence of alkaline earth elements avoids the formation of insulating and inactive carbonates during CO2 electrolysis. It is worth noting that Fe2TiO5-δF0.2 undergoes an ingenious phase transition during the electrolysis process, generating the heterogeneous Fe/FeTiO3-δF0.2 interface as the active center. The resulting cathode (Fe/FeTiO3-δF0.2) demonstrates good activity and stability for pure CO2 electrolysis. The current density is close to 2.0 A cm−2 at 1.6 V (850 °C) and the electrolysis voltage keeps near-constant during the 235 h galvanostatic test at 0.4 A cm−2 (800 °C). The newly formed heterogeneous Fe/FeTiO3-δF0.2 microstructure is believed to be suitable for other catalytic processes.