Strongly Coupled FeNi Alloys/NiFe₂O₄@Carbonitride Layers-Assembled Microboxes for Enhanced Oxygen Evolution Reaction

Hydrogen produced from electrocatalytic water splitting is a promising route due to the sustainable powers derived from the solar and wind energy. However, the sluggish kinetics at the anode for water splitting makes the highly effective and inexpensive electrocatalysts desirable in oxygen evolution reaction (OER) by structure and composition modulations. Metal-organic frameworks (MOFs) have been intensively used as the templates/precursors to synthesize complex hollow structures for various energy-related applications. Herein, an effective and facile template-engaged strategy originated from bimetal MOFs is developed to construct hollow microcubes assembled by interconnected nanopolyhedron, consisting of intimately dominant FeNi alloys coupled with a small NiFe₂O₄ oxide, which was confined within carbonitride outer shell (denoted as FeNi/NiFe₂O₄@NC) via one-step annealing treatment. The optimized FeNi/NiFe₂O₄@NC exhibits excellent electrocatalytic performances toward OER in alkaline media, showing 10 mA·cm^-2 at η = 316 mV, lower Tafel slope (60 mV·dec^-1), and excellent durability without decay after 5000 CV cycles, which also surpasses the IrO₂ catalyst and most of non-noble catalysts in the OER, demonstrating a great perspective. The superior OER performance is ascribed to the hollow interior for fast mass transport, in situ formed strong coupling between FeNi alloys and NiFe₂O₄ for electron transfer, and the protection of carbonitride layers for long stability.