In situ passivation of Fe nanoparticles exsolved from perovskite cathodes through zinc doping for CO2 electrolysis

Abstract

Efficiently converting CO₂ into value-added fuels or chemicals is a significant target for reducing CO₂ emissions and achieving carbon neutrality. Solid oxide electrolysis cells (SOECs) are devices where the CO₂ reduction reaction (CO₂RR) takes place with high efficiency and fast kinetics at high temperatures. Since the CO₂RR occurring at the cathode side is a sluggish reaction over whole electrode reactions, it is crucial to develop innovative cathode materials with high activity and good durability. Here, we demonstrate a strategy to synergistically optimize the bulk properties of Sr₂Fe_1.5Mo_0.5O_6−δ (SFM) and the morphology of the exsolved nanoparticles (NPs) to enhance the CO₂RR activity, electrochemical performance, and durability. The partial replacement with zinc in the Fe-site of SFM not only increases the oxygen vacancy concentration of perovskite bulk and improves the CO₂ adsorption capacity, but also passivates in situ exsolution of Fe NPs and improves the active sites on the perovskite surface, thus enhancing CO₂ electrolysis performance. A novel cathode, Sr₂Fe_1.4Zn_0.1Mo_0.5O_6−δ (SFZM01), used in a La_0.8Sr_0.2Ga_0.8Mg_0.2O_3−δ electrolyte-supported single cell, shows a high current density of 2.74 A cm⁻² at 850 °C (1.6 V) and excellent durability when operated at a current density of −1.0 A cm⁻² at 750 °C. These findings can guide the development of high-activity and stability catalysts for carbon capture and utilization.