Melt-Spun FeCrNiMoC0.3 High-Entropy Alloy Ribbons: Microstructure Refinement for Enhanced Bifunctional Alkaline Overall Water Splitting

Alkaline water electrolysis urgently requires scalable, binder-free integrated bulk electrodes with high activity and robust stability at high current densities. High-entropy alloys (HEAs) are promising candidates for such electrodes, but conventional as-cast HEAs generally suffer from coarse grains, which limits their electrocatalytic performance. Herein, FeCrNiMoC0.3 HEA ribbons were fabricated as integrated electrocatalysts via melt-spinning rapid solidification. This metallurgical treatment refines matrix grains to an average size of 135.7 nm, uniformly disperses nanoscale carbides, induces FCC lattice expansion, and drives directional charge transfer from Fe/Cr/Ni to Mo without altering the phase composition. In 1.0 M KOH, the melt-spun ribbons (MSRs) exhibit enhanced bifunctional electrocatalytic performance. At 10 mA cm–2, the MSR electrode delivers overpotentials of 218 mV for the oxygen evolution reaction (OER) and 81 mV for the hydrogen evolution reaction (HER), with Tafel slopes of 30.8 and 55.4 mV dec–1, respectively. The two-electrode overall water splitting achieves 500 mA cm–2 at 2.03 V and runs stably for over 500 h. Grain and carbide refinement, accompanied by electronic modulation, an enlarged electrochemically active surface area, and reduced charge transfer resistance, collectively accounts for the enhanced performance. This work provides a facile and scalable metallurgical strategy to optimize carbide-containing binder-free bulk HEAs and offers a reference for understanding the microstructure–activity relationship of bulk alloy electrodes for alkaline water electrolysis.