Engineering highly active oxygen sites in perovskite oxides for stable and efficient oxygen evolution

Perovskite oxides, represented by Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ (BSCF), with O anion partially substituted by F anion are designed. Introduction of F in perovskite lattice initiated the transition of Co(III) and Fe(III) species to lower oxidation states and triggered the surface O anion to be activated to highly oxidative O²⁻/O^‒, which is deemed to be efficient active sites for oxygen evolution reaction (OER) catalysis. As a consequence, the F substituted BSCF (F-BSCF) catalyst exhibits outstanding electrocatalytic activity with overpotential of only 280 mV to deliver 10 mA cm^‒2 OER, which is among the results for state-of-the-art metal oxide based catalysts. Strikingly, an stable chronoamperometric response prolonged for 100 h and an impressive cycling stability demonstrate its prominent durability, much superior to the commercial IrO₂ catalyst. These findings highlight the promising potential of F substitution as an efficient strategy for active site engineering in traditional precious metal-free OER electrocatalysts.