Perovskite oxide is an attractive low-cost alternative catalyst for oxygen evolution reaction (OER) relative to the precious metal oxide-based electrocatalysts (IrO and RuO). In this work, a series of Sr-doped La-based perovskite oxide catalysts with compositions of LaSr FeO ( x = 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 (LF), LaSrFeO (LSF-0.2), LaSrFeO (LSF-0.5), SrFeO (SF), and LaSrFeO (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.

Exploring active, stable, and low‐cost bifunctional electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is crucial for water splitting technology associated with renewable energy storage in the form of hydrogen fuel. Here, a newly designed antiperovskite‐based hybrid composed of a conductive InNNi3 core and amorphous InNi(oxy)hydroxide shell is first reported as promising OER/HER bifunctional electrocatalyst. Prepared by a facile electrochemical oxidation strategy, such unique hybrid (denoted as EO‐InNNi3) exhibits excellent OER and HER activities in alkaline media, benefiting from the inherent high‐efficiency HER catalytic nature of InNNi3 antiperovskite and the promoting role of OER‐active InNi(oxy)hydroxide thin film, which is confirmed by theoretical simulations and in situ Raman studies. Moreover, an alkaline electrolyzer integrated EO‐InNNi3 as both anode and cathode delivers a low voltage of 1.64 V at 10 mA cm−2, while maintaining excellent durability. This work demonstrates the application of antiperovskite‐based materials in the field of overall water splitting and inspires insights into the development of advanced catalysts for various energy applications.

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