The slow activity of cathode materials is one of the most significant barriers to realizing the operation of solid oxide fuel cells below 500 °C. Here we report a niobium and tantalum co-substituted perovskite SrCo0.8Nb0.1Ta0.1O3−δ as a cathode, which exhibits high electroactivity. This cathode has an area-specific polarization resistance as low as ∼0.16 and ∼0.68 Ω cm2 in a symmetrical cell and peak power densities of 1.2 and 0.7 W cm−2 in a Gd0.1Ce0.9O1.95-based anode-supported fuel cell at 500 and 450 °C, respectively. The high performance is attributed to an optimal balance of oxygen vacancies, ionic mobility and surface electron transfer as promoted by the synergistic effects of the niobium and tantalum. This work also points to an effective strategy in the design of cathodes for low-temperature solid oxide fuel cells.

A highly defective CeO2 supported RuO2 as an electrocatalyst shows improved OER activity and stability in alkaline media. This improvement likely originates from the highly oxidative oxygen species O22−/O− formed in the defective CeO2, which can easily migrate from CeO2 and “spillover” to the surface of RuO2 during the OER process.

Strontium cobaltite-based perovskites (SrCoO3−δ) have been widely studied as a promising cathode for the next-generation solid-oxide fuel cell (SOFC). Here, we found a balance between oxygen vacancy (VO) formation and its migration in designing SrCoO3−δ-based materials by using two activity descriptors, i.e., radius and electronegativity. The ORR activity of these types of perovskites is found to strongly rely on the two proposed descriptors, and Nb- or Ta-doped SrCoO3−δ locates in the promising zone as predicted with a moderate value of both VO formation energy and ion migration barrier. Then Sc–Ta co-doped SrCoO3−δ (SSTC) and Sc–Nb co-doped SrCoO3−δ (SSNC) are screened out to be the best among 91 bimetal-doped SrCoO3−δ perovskites. Further experiments have been carried out to synthesize the co-doped SSTC and prove ultralow area-specific resistance values (0.071, 0.198, and 0.701 Ω·cm2 at 550, 500, and 450 °C, respectively), which is only one-third of that of benchmark materials for the SOFC cathodes. Our results open a novel pathway in designing SOFC cathodes with an optimal performance.

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