Lewis Basicity Enhanced SrFeO_3-δ-Based Perovskite Fuel Electrode for Surface and Bulk Processes Co-Accelerated CO₂...

Electroreduction of CO₂ to CO by solid oxide electrolysis cells (SOEC) is an effective means to realize carbon neutralization. However, the sluggish kinetics at SOEC fuel electrode impedes its further practical application. Herein, the doping strategy of cesium ion (Cs¹⁺) is employed to develop a series of perovskite-type fuel electrode materials, i.e., Cs_xSr_1-xFe_0.9Nb_0.1O_3-δ (x = 0.05, 0.1, 0.15). Combining the results of experiments and theoretical calculations, it is found that the introduction of Cs¹⁺ into A-site of SrFeO_3-δ-based perovskite accelerates the reaction kinetics of CO₂ adsorption and dissociation due to increased lattice oxygen basicity caused by the low electronegativity of Cs¹⁺. In addition, in comparison to Sr²⁺, the larger ionic radius and lower valence of Cs¹⁺ is beneficial to decrease formation energy of oxygen vacancy and migration barrier of oxygen ion in perovskite bulk. Because of those merits brought by Cs¹⁺ doping, the La_0.8Sr_0.2Ga_0.8Mg_0.2O_3-δ electrolyte-supported electrolysis cells with Cs_0.1Sr_0.9Fe_0.9Nb_0.1O_3-δ fuel electrode presents satisfied current density of 2205 mA cm^-2 at 1.6 V and 850 °C. The stable long-term operation of electrolysis cells is also demonstrated at applied current density of 600 mA cm^-2 and 800 °C for 100 h.