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High-efficiency and low-cost catalysts for the oxygen evolution reaction (OER) in acidic electrolytes are critical for electrochemical water splitting in proton exchange membrane (PEM) electrolyzers to produce green hydrogen, a clean fuel for sustainable energy conversion and storage. Among OER catalysts, solid-state synthesized SrCo1−xIrxO3 has demonstrated superior activity compared to commercial standards, such as IrO2 and RuO2. However, the solid-state synthesis process is economically inefficient for industrial use due to the potential for impurities and low yield of the final product. In addition, the requirement for electrochemical cycling to activate the catalyst introduces contaminations and uncertainties for industrial applications. In this study, a modified solution-based sol–gel method was employed to produce SrCo0.5Ir0.5O3 (SCIO) with high purity and yield. Subsequent ball milling and acid leaching treatments were applied, resulting in a catalyst with higher efficiency than those activated solely by electrochemical cycling. The electrochemical analysis and physical characterizations of our SCIO catalyst after ex-situ post-synthesis treatments show a similar active phase in composition and structure to those obtained through in situ electrochemical cycling and activation. Our approach simplifies the preparation process, making the catalyst ready for direct use in PEM electrolyzers without further treatment, offering a promising solution for producing high-performance, industrial-scale OER catalysts. 

Abstract Iron is a promising candidate for a cost‐effective anode for large‐scale energy storage systems due to its natural abundance and well‐established mass production. Recently, Fe‐ion batteries (FeIBs) that use ferrous ions as the charge carrier have emerged as a potential storage solution. The electrolytes in FeIBs are necessarily acidic to render the ferrous ions more anodically stable, allowing a wide operation voltage window. However, the iron anode suffers severe hydrogen evolution reaction with a low Coulombic efficiency (CE) in an acidic environment, shortening the battery cycle life. Herein, a hybrid aqueous electrolyte that forms a solid‐electrolyte interphase (SEI) layer on the Fe anode surface is introduced. The electrolyte mainly comprises FeCl₂and ZnCl₂as cosalts, where the Zn‐Cl anionic complex species of the concentrated ZnCl₂allows dimethyl carbonate (DMC) to be miscible with the aqueous ferrous electrolyte. SEI derived from DMC's decomposition passivates the iron surface, which leads to an average CE of 98.3% and much‐improved cycling stability. This advancement shows the promise of efficient and durable FeIBs.