Hidden Kinetic and Degradation Domains in Alkaline Electrolysis Revealed by Electrode-Resolved Diagnostics: Article No. 241300

Reference electrode-integrated diagnostics were used to separate kinetic, ohmic, and mass-transport losses in a zero-gap alkaline water electrolyzer (AWE) using a binder-free RuOx cathode and a Raney Ni anode, achieving 1.58?V at current density of 1Acm-2. Temperature-dependent analysis revealed fundamentally different charge-transfer domains at the two electrodes: hydrogen evolution on RuOx followed classical activation-controlled kinetics, while oxygen evolution on Raney Ni presented non-classical behavior consistent with intermediate-mediated charge transfer. Durability studies identified a previously unresolved potential-dependent instability window near ~1.6?V vs RHE. Operation near this regime accelerated Al and Ni leaching from the Raney Ni framework through dynamic phase transitions, causing pronounced anode degradation. Dissolved species were subsequently transported through the electrolyte and redeposited on the cathode, forming electrochemically inactive surface domains that suppressed hydrogen evolution. In contrast, operation at higher anodic potentials stabilized NiOOH phases, reduced metal dissolution, and improved durability. Open-circuit-voltage cycling reproduced the same degradation pathway, confirming the critical role of low-potential exposure. Controlled Fe-addition experiments further revealed a dual effect of impurities, enhancing OER activity through NiFeOOH formation while simultaneously suppressing HER by cathode deposition. These results establish design principles for optimizing operating windows, impurity management, and long-term AWE durability.