Boosting CO₂ electrolysis via synergy between active heterogeneous interface and oxygen defects

The commercial viability of solid oxide electrolysis cells (SOECs) for the electrochemical reduction of CO₂ to CO is hampered by the sluggish electrocatalytic activity of the electrode materials. In this study, a series of perovskites, Pr_0.5Sr_0.5Cr_0.1Fe_0.9-xNi_xO_3-δ (x = 0.1, 0.2, PSCFN_x) with different Ni doping levels were synthesized. The results showed that increasing Ni doping led to the creation of more oxygen vacancies. Furthermore, treatment of PSCFN_x in a reducing atmosphere resulted in a structural transformation into a composite with a heterogeneous interface between the Ruddlesden-Popper perovskite (RP-PSCFN_x) and an exsolved Ni-Fe metal alloy. The re-PSCFN_0.2-based cell showed a current density of 2.40 A cm⁻² and a Faraday efficiency (FE%) of almost 100 % at 850 °C and 1.6 V, an improvement of 18 % in comparison to the re-PSCFN_0.1-based cell. This study provides a strategy to synergistically improve the electrochemical reduction of CO₂ activity of SOECs by constructing an active heterogeneous interface and increasing the oxygen vacancy content.