A‐site Cation Defects (Ba0.5Sr0.5)1–xCo0.8Fe0.2O3–δ Perovskites as Active Oxygen Evolution Reaction Catalyst in Alkaline Electrolyte†

Main observation and conclusion Perovskites (Ba 0.5 Sr 0.5 ) 1– x Co 0.8 Fe 0.2 O 3– δ ( x = 0.02, 0.05, 0.1 denoted as BSCF‐0.98, BSCF‐0.95, BSCF‐0.9, respectively) with A‐site cation defects are synthesized by simple and efficient sol‐gel method and are proved to have better OER catalytic effect than the well‐known Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3– δ (BSCF) oxides. BSCF‐0.95 exhibits the best OER catalytic activity in the series perovskite. The current density of BSCF‐0.95 is about 56% higher than that of BSCF oxide at a potential of 1.7 V. The experimental studies have shown that compared with BSCF, BSCF‐0.95 oxide has a larger electrochemical surface area (ECSA), a higher content of O 2 2– species related to surface oxygen vacancies, and faster charge transfer rate, which may be the factors for the enhancement of OER activity. The theoretical calculation results prove that the center positions of the O 2p‐band of perovskite with A‐site cation defects are closer to the Fermi level than BSCF oxide, which agrees with the OER performance trend of the material.