Microwave-Induced Dense Crystal–Amorphous Fe_<i>x</i>Ni_<i>y</i>OOH Nanosheets as Stable Electrocatalysts for Oxygen Evolution

Interfacial engineering between crystallin and amorphous phases plays a significant role in the development of highly efficient and stable electrocatalysts. Conventional heterostructures synthesized via asynchronous methods often suffer from limited interfacial density, which compromises their durability. Here, we present densely integrated crystalline–amorphous FexNiyOOH nanosheets synthesized via a one-step microwave thermal shock strategy. This dense crystalline–amorphous architecture confers exceptional structural and operational stability and enables continuous oxygen evolution reaction (OER) operation at 10 mA cm–2 for over 1000 h without significant degradation. Density functional theory (DFT) calculations attribute the sustained performance to the stable spin-state modulation at the high-density interfaces, where the Fe-induced high-spin nickel optimizes intermediate adsorption while preserving stable Fe site activity. The achievement of a low overpotential of 243 mV at 10 mA cm–2 and the unprecedented longevity offer valuable insights for advancing the design of durable electrocatalysts toward practical commercialization.