Highly efficient bifunctional oxygen electrocatalysts are indispensable for the development of highly efficient regenerative fuel cells and rechargeable metal-air batteries, which could power future electric vehicles. Although perovskite oxides are known to have high intrinsic activity, large particle sizes rendered from traditional synthesis routes limit their practical use due to low mass activity. We report the synthesis of nano-sized perovskite particles with a nominal composition of Lax(Ba0.5Sr0.5)1−xCo0.8Fe0.2O3−δ (BSCF), where lanthanum concentration and calcination temperature were controlled to influence oxide defect chemistry and particle growth. This approach produced bifunctional perovskite electrocatalysts ∼50 nm in size with supreme activity and stability for both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The electrocatalysts preferentially reduced oxygen to water (<5% peroxide yield), exhibited more than 20 times higher gravimetric activity (A g−1) than IrO2 in OER half-cell tests (0.1 M KOH), and surpassed the charge/discharge performance of Pt/C (20 wt%) in zinc-air full cell tests (6 M KOH). Our work provides a general strategy for designing perovskite oxides as inexpensive, stable and highly active bifunctional electrocatalysts for future electrochemical energy storage and conversion devices.
