Structural Engineering of Crystalline–Amorphous NiFeMn Alloy and Trimetallic Phosphite Heterostructure Electrocatalysts for High-Performance Industrial Anion Exchange Membrane Water Electrolysis

The scalability of water electrolysis technology for green hydrogen generation hinges on the advancement of oxygen evolution reaction (OER) catalysts with enhanced durability and cost efficiency. A critical unresolved challenge lies in achieving sustained stability under industrial conditions. In this work, we synthesized dual-phase NiFeMn@triMPi nanocomposites via a one-pot liquid-phase method, embedding crystalline NiFeMn nanoparticles in an amorphous trimetallic phosphite matrix. These heterostructures serve as efficient OER electrocatalysts in anion exchange membrane electrolyzers, achieving long-term stability at ampere-level current densities. The prepared electrodes achieve a relatively high activity of 2800 mA cm^-2 at 2.0 V and show long-term durability of 1000 h (80 °C and 1000 mA cm^-2) with a decay rate of 8.3 μV h^-1. In situ Raman spectroscopy and structural characterization reveal that the crystalline-amorphous heterostructures modify the electronic properties and surface microenvironments, facilitating deep and rapid surface reconstruction into a dynamically stable NiFeMn@NiFeMn LDH phase during operation. This study establishes a strategic framework for developing high-performance crystalline-amorphous heterostructured catalysts, providing a generalized solution to stability issues in industrial water electrolyzers operating at elevated temperatures and ampere-level current densities.