Effects of B-site doping and stoichiometry on strontium ferrate Sr0.85Ce0.15FexCoyO3 perovskites as electrocatalysts

SrFeO₃-based oxides are multi-functional ceramics belonging to the ABO₃-type perovskite family, where iron is interestingly present at the B-site as Fe⁴⁺ and partially reducible to Fe³⁺ by doping strategies to tailor the physical–chemical properties. When doped, fine-tuned SrFeO₃ is exploitable in novel energy production systems, for example, electrocatalysts in intermediate temperature solid oxide fuel cells (IT-SOFCs). This work aimed to evaluate how the B-site composition and stoichiometry affect the functional properties of SrFeO₃-based materials when A-site doping with cerium is fixed at 15 mol%. Hence, powdered samples were prepared by solution combustion synthesis, modulating the Fe/Co ratio or the B-site stoichiometry (Fe + Co). From an in-depth characterization, it was found that both B-site nonstoichiometry and Fe/Co ratio influenced structure, redox properties, and electrochemical behavior. Still, nonstoichiometry played a major role in improving oxygen adsorption capacity and mobility, also thanks to the contribution of the segregated phases (CeO₂, Sr₃Fe₂O_7−δ) generated by the induced B-site unbalancing. The nonstoichiometric sample reached the highest oxygen reduction capability at the IT-SOFC operating temperature (600°C) and the lowest activation energy (0.65 eV), whereas the cobalt-rich sample showed poorer performance as an oxygen electrode. These results encourage further research on tunable cobalt-poor and nonstoichiometric perovskites in energy-related devices.