Cathode passivation suppression enables ultrastable industry-leading alkaline water electrolysis at hundred-ampere currents

Abstract

Industry-leading alkaline water electrolysis (AWE) remains limited by low current densities (<0.3 A cm⁻²) due to cathodic oxidation-induced passivation of commercial RANEY® Ni cathodes under operation. This generates interfacial Ni(OH)₂/NiOOH insulating layers, impeding electron transfer and increasing resistance, thereby capping current density. Herein, we proposed a passivation-inhibition strategy by reconstructing the water network structure at the electrode interface via introducing Ru nanoparticles (Ru_NPs) on RANEY® Ni (Ru_NPs@RANEY® Ni). We found that the orientation changes of interfacial water accelerated water dissociation, thereby altering the localized pH and facilitating the mass transfer of hydroxide ions at the electrode interface. This process suppressed the positive shift in electrode potential, closely associated with passivation-inhibition mechanisms. The AWE electrolyzers with Ru_NPs@RANEY® Ni delivered an extremely high current density of 10 A cm⁻² at a low cell voltage of 2.3 V with exceptional stability over 2500 hours at 1.0 A cm⁻². The system achieved an energy consumption of 4.20 kWh Nm⁻³ H₂, with an energy efficiency of 84.2% (based on the higher heating value of hydrogen) at 1.0 A cm⁻², a H₂ production rate of 41.2 NL h⁻¹ and a production cost of 0.93 $ kg⁻¹ H₂ at 100 A (over a 100 cm² electrode area), undercutting U.S. DOE's 2026 target. These findings demonstrate that mitigating cathode passivation is critical for high performance AWE electrolyzers.