Pulse Electrodeposited NiFeCoMoW High-Entropy Alloy Electrode for Efficient Alkaline Water Electrolysis

High-entropy alloys (HEAs) offer a versatile platform for bifunctional electrocatalysis, yet their activity-stability balance under industrial-level current density remains insufficiently understood. Here, we report a self-supported NiFeCoMoW HEA electrode fabricated by pulse electrodeposition on copper foam, forming a binder-free hierarchical architecture with homogeneous elemental distribution. In 1.0 M KOH, NiFeCoMoW@CF delivers strong bifunctional activity, requiring an overpotential of 251 mV to reach 10 mA cm^-2 for OER, and enables overall water splitting with a low cell voltage of 1.52 V at 10 mA cm^-2 and 1.83 V at 1000 mA cm^-2. The electrolyzer operates stably at 1000 mA cm^-2 for 100 h with minimal voltage increase. In situ Raman spectroscopy reveals a potential-dependent surface evolution: a persistent Mo/W-O signature is retained across HER and OER, while Ni/Fe/Co reconstruct into an oxyhydroxide-rich surface state under OER, consistent with post-test XPS/HRTEM. This coupled stabilization-reconstruction behavior, enabled by multicomponent coupling and pulse-engineered accessibility, provides mechanistic insight and a practical strategy for durable, noble-metal-free alkaline water electrolysis.