Linking Pulse‐Duration‐Controlled Laser Nanostructuring to Oxygen Evolution Kinetics in Fe‐enriched NiOx Electrodes

ABSTRACT The oxygen evolution reaction (OER) remains the main kinetic and energetic bottleneck in alkaline water electrolysis, motivating scalable and durable electrocatalysts based on earth‐abundant materials. Nickel oxide systems, especially when transformed into NiOOH/NiFeOOH phases, are among the most promising non‐precious OER catalysts; however, conventional synthesis and binder‐based fabrication often restrict control over morphology, active‐site accessibility, and stability. Here, pulse‐duration‐controlled ultra‐short pulsed laser processing (ULPING) is established as a binder‐free and scalable route to directly fabricate nanostructured NiOx electrodes while systematically linking fabrication physics to OER kinetics. By varying pulse duration from 150 ps to 5 ns under otherwise identical irradiation, pulse duration is shown to govern ablation depth, nanostructure growth height, and hierarchical porosity. Shorter pulses produce rough, defect‐rich, broccoli‐like NiOx architectures with high nano‐area gain, whereas longer pulses lead to deeper craters and smoother, melt‐dominated morphologies. Modeling of transient temperature fields and ablation profiles explains the observed topographical evolution. Electrochemical measurements reveal a strong correlation between pulse‐duration‐controlled morphology, redox‐accessible Ni 2 + /Ni 3 + active‐site density, and OER performance. The low‐pulse‐duration electrode shows lower overpotential, reduced charge‐transfer resistance, favorable Tafel slopes, and further enhancement after Fe incorporation. Stable operation at 50 mA cm − 2 for 25 h confirms excellent durability and preserved nanostructural integrity.