Summary This work demonstrates that a multi-phase catalyst coating (∼30 nm thick), composed of BaCoO 3−x (BCO) and PrCoO 3−x (PCO) nanoparticles (NPs) and a conformal PrBa 0.8 Ca 0.2 Co 2 O 5+δ (PBCC) thin film, has dramatically enhanced the rate of oxygen reduction reaction (ORR). When applied to a state-of-the-art La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 (LSCF) cathode in a solid oxide fuel cell (SOFC), the catalyst coating reduced the cathodic polarization resistance from 2.57 to 0.312 Ω cm 2 at 600°C. Oxygen molecules adsorb and dissociate rapidly on the NPs due to enriched surface oxygen vacancies and then quickly transport through the PBCC film, as confirmed by density functional theory-based computations. The synergistic combination of the distinctive properties of the two separate phases dramatically enhances the ORR kinetics, which is attractive not only for intermediate-temperature SOFCs but also for other types of energy conversion and storage systems, including electrolysis cells and membrane reactors for synthesis of clean fuels.
