A Highly Efficient Multi-phase Catalyst Dramatically Enhances the Rate of Oxygen Reduction

This work demonstrates that a multi-phase catalyst coating (∼30 nm thick), composed of BaCoO3−x (BCO) and PrCoO3−x (PCO) nanoparticles (NPs) and a conformal PrBa0.8Ca0.2Co2O5+δ (PBCC) thin film, has dramatically enhanced the rate of oxygen reduction reaction (ORR). When applied to a state-of-the-art La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) cathode in a solid oxide fuel cell (SOFC), the catalyst coating reduced the cathodic polarization resistance from 2.57 to 0.312 Ω cm2 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.