Systematic Study of Oxygen Evolution Activity and Stability on La<sub>1–<i>x</i></sub>Sr<sub><i>x</i></sub>FeO<sub>3−δ</sub> Perovskite Electrocatalysts in Alkaline Media

Perovskite oxide is an attractive low-cost alternative catalyst for oxygen evolution reaction (OER) relative to the precious metal oxide-based electrocatalysts (IrO<sub>2</sub> and RuO<sub>2</sub>). In this work, a series of Sr-doped La-based perovskite oxide catalysts with compositions of La<sub>1–<i>x</i></sub>Sr<sub><i>x</i></sub>FeO<sub>3−δ</sub> (<i>x</i> = 0, 0.2, 0.5, 0.8, and 1) are synthesized and characterized. The OER-specific activities in alkaline solution increase in the order of LaFeO<sub>3−δ</sub> (LF), La<sub>0.8</sub>Sr<sub>0.2</sub>FeO<sub>3−δ</sub> (LSF-0.2), La<sub>0.5</sub>Sr<sub>0.5</sub>FeO<sub>3−δ</sub> (LSF-0.5), SrFeO<sub>3−δ</sub> (SF), and La<sub>0.2</sub>Sr<sub>0.8</sub>FeO<sub>3−δ</sub> (LSF-0.8). We establish a direct correlation between the enhancement in the specific activity and the amount of surface oxygen vacancies as well as the surface Fe oxidation states. The improved specific activity for LSF-0.8 is clearly linked to the optimum amount of surface oxygen vacancies and surface Fe oxidation states. We also find that the OER performance stability is a function of the crystal structure and the deviation in the surface La and/or Sr composition(s) from their bulk stoichiometric compositions. The cubic structure and lower deviation, as is the case for LSF-0.8, led to a higher OER performance stability. These surface performance relations provide a promising guideline for constructing efficient water oxidation.