Catalytic Mechanism of Nanocrystalline and Amorphous Matrix in Fe‐Based Microwires for Advanced Oxidation

Abstract The sustainable management of water resources is a critical global challenge, with advanced oxidation processes emerging as a promising solution for addressing environmental water pollution. However, the clear trade‐off between catalytic activity and stability in existing environmental catalysts hinders their broader application. In this study, a nanocrystalline/amorphous (N/A) microwire catalyst is developed, featuring a design that regulates nanocrystal size while preserving a pure amorphous matrix. Unlike brittle annealed N/A microwires subjected to structural relaxation, the as‐cast N/A microwires demonstrate outstanding catalytic performance for advanced oxidation. They can completely degrade pollutants within 60 s and maintain their activity for up to 40 reuse cycles. Theoretical calculations and material characterizations reveal that the exceptional properties of the as‐cast N/A microwires arise from the combined effects of residual stresses stored in the amorphous matrix and the synergistic effect between nanocrystals and amorphous phases. Moreover, the optimally sized nanocrystalline phase optimizes the atomic arrangement and induces an atomic structure with a low atomic coordination number, providing abundant active sites. This design also enhances the adsorption characteristics of persulfate and accelerates electron transfer. These findings offer a novel design framework for developing efficient and stable catalysts for wastewater treatment.