Tailoring Nanocrystalline/Amorphous Interfaces to Enhance Oxygen Evolution Reaction Performance for FeNi‐Based Alloy Fibers

Abstract Efficient oxygen evolution reaction (OER) electrocatalysts play a pivotal role in water electrolysis, notably for industrial high current densities (>1000 mA cm −2 ). Crystalline/amorphous heterostructure interfaces have proven to be advantageous for enhancing the OER activities of electrocatalytic materials. However, the constructing and tailoring for crystalline/amorphous interfaces still remain a great challenge due to the destruction of active substrates by intricate post‐treatment. Here, a strategy to tailor nanocrystalline/amorphous (N/A) interface and optimize the electrocatalytic performance of as‐cast N/A alloys by adjusting the size of nanocrystals is proposed. The N/A alloy fibers obtained based on this strategy exhibit superior OER performance with an overpotential of 227 mV (@10 mA cm −2 ), maintaining stability for over 1000, 600, and 240 h under high current densities of 500, 1000, and 1800 mA cm −2 , respectively. Theoretical calculations and material characterizations reveal that N/A interfaces, facilitated by appropriately sized nanocrystals possessing a loose atomic arrangement, favorable surface electronic structure, advantageous local coordination, and optimal O‐contained intermediate adsorption, can yield abundant active sites without compromising stability. This study not only provides a deeper understanding of the tailoring mechanism of N/A interfaces but also offers a new design perspective for the development of cost‐effective, industrial‐grade electrocatalysts.