Novel, cobalt-free, and highly active Sr₂Fe_1.5Mo_0.5−xSn_xO_6−Δ cathode materials for intermediate temperature solid oxide fuel cells

One of the technical hurdles to commercialization of intermediate temperature solid oxide fuel cells (IT-SOFCs) is the requirement of highly efficient cathode materials. Herein, we report the evaluation of Sr₂Fe_1.5Mo_0.5−xSn_xO_6−δ (x = 0, 0.1, 0.3 and 0.5, abbreviated as SFM, SFMS1, SFMS3, and SFS) oxides as cobalt-free cathode materials of IT-SOFCs. XPS analysis demonstrates the presence of variable valences among Fe, Mo and Sn elements, suggesting a small polaron hopping mechanism for electronic conduction. First principle calculations reveal that SFMS3 provides the lowest average formation energy of oxygen vacancy (E_vacO*) among these perovskites. The relatively low area specific resistances are obtained with SFMS3 electrode based on La_0.8Sr_0.2Ga_0.8Mg_0.2O_3−δ electrolytes, indicating its high activity for oxygen reduction reaction. Power density of the single cell using SFMS3 cathode as high as 618 mW cm⁻² at 800 °C is achieved, and operation lasts for 200 h without obvious degradation. The encouraging results promise SFMS3 as an alternative cathode material for IT-SOFCs. © 2017 Hydrogen Energy Publications LLC