Mechanochemical Activation of Nickel Oxide: A Pivotal Step in the Process Chain Enabling Binder-Free Anodes for Alkaline Water Electrolysis

Abstract Sustainable hydrogen production via alkaline water electrolysis demands robust electrocatalysts for the oxygen evolution reaction (OER) that combine performance with scalability. We address this by mechanochemical activation of nickel oxide (NiO) to fabricate binder-free anodes. First, we investigated the effects of planetary ball milling (PBM), which decreased crystallite size, increased specific surface area, elevated Ni3+ content, and enhanced the amount of surface hydroxyl groups. PBM with larger beads induced more pronounced structural transformations due to higher impact forces. Mechanochemically activated NiO showed a lower overpotential than bare nickel (365 vs. 377 mV at 100 mA cm–2 in 1 M KOH) with excellent particle cohesion, enabling mechanically stable, binder-free anodes. We translated this approach to continuously operable stirred media milling, enabling mechanochemical activation and concurrent ink formulation in isopropanol, eliminating intermediate powder drying as needed in the case of PBM. The resulting anodes exhibited an even lower overpotential (343 mV) and higher mechanical robustness, offering a binder-free pathway for OER electrode fabrication.