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

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.