Reverse‐Current Induced Cascade Degradation in Ni–Ru Electrodes: Tracing the Path from Noble Metal Loss to Substrate Corrosion

Abstract Long‐term durability of Ni‐based electrodes under renewable energy (RE) driven dynamic operation, remains a critical bottleneck in advancing the alkaline water electrolysis (AWE). Among various durability‐related failure behaviors, degradation induced by reverse current (RC) has been largely overlooked, despite its growing relevance under fluctuating RE. Herein, we systematically elucidate a multistage degradation pathway of Ni–Ru electrodes (NR) under an accelerated stress test (AST). By combining full‐process electrochemical monitoring with morphological and compositional analysis the pathway is summarized as follow: (i) the dense Ru layer is initially oxidated into rough and defective surface with high surface area, under the Ostwald ripening effect; (ii) promoted by the gradual formation of the Ni–Ru co‐exposure to the electrolyte, the Ni substrate is subsequently galvanic corroded accompanied by partial Ru redeposition; (iii) through prolonged operation, both Ni and Ru are extensively oxidated and precipitated, eventually resulting in complete Ru depletion and structural collapse of Ni substrate. Based on this mechanistic understanding, we further investigate the effect of RC amplitude on degradation kinetics. Reducing the RC amplitude fraction from 20% to 0%, the initial Ru oxidation is effectively suppressed and following failure is thereby mitigated, with decreasing the degradation rate from 4.756 to 0.257 mV h ⁻¹ . These findings provide with fundamental insight into dynamic degradation evolution and offer practical mechanism for RC‐tolerant electrode design.