Investigating Precursor pH Effects on the Electrocatalytic Properties of Mn–Fe Oxides for Zinc–Air Batteries

Here, we report a two‐step electrochemical route to fabricate binder‐free gas diffusion electrodes (GDEs) incorporating Mn–Fe oxide (MnFeO) catalysts for rechargeable zinc–air (Zn–air) batteries (ZABs). A series of MnFeO catalysts was synthesized by varying the precursor pH, enabling systematic tuning of the Fe ²⁺ /Mn ³⁺ composition, oxidation states, and catalyst structure. Among the as‐prepared catalysts, precursor pH strongly influenced the Mn/Fe distribution, oxidation‐state composition, and spinel structure. Following electrochemical testing, distinct pH‐dependent reconstruction pathways were observed, resulting in marked differences in catalytic activity and durability. To establish the relationship between the initial catalyst structure and its operationally evolved state, structural analyses were performed before electrochemical testing and after complete electrochemical performance and stability tests. Comparative SEM, Raman, and XPS analyses revealed distinct reconstruction pathways. Under electrochemical operating conditions, MnFeO_pH5 underwent controlled surface reconstruction to form a catalytically active NiOOH‐like/(Mn–Fe)‐modified oxyhydroxide layer while preserving the integrity of the bulk catalyst structure. The results indicate that long‐term electrocatalytic performance is governed by the initial oxidation‐state distribution and the catalyst's ability to form a stable reconstructed active phase under operating conditions. These findings demonstrate that precursor pH engineering provides an effective strategy for tailoring the activity and durability of Mn–Fe oxide electrocatalysts for rechargeable ZABs.