Laterally Oriented Dendritic Passivation via In Situ Zn Reconstruction for Stabilizing NiMo Catalysts under Dynamic Electrolysis

This study highlights the effectiveness of Zn‐induced dendrite layers in enhancing the durability of NiMo HER catalysts under dynamic electrochemical conditions. Through in situ dendritic passivation, the Zn‐NiMo catalyst preserves catalytic active sites and mitigates irreversible Ni oxidation/hydroxylation during repeated load fluctuation. ABSTRACT Integrating water electrolyzers with intermittent renewable energy poses critical durability challenges from dynamic load fluctuations inducing catalyst degradation. We report a zinc‐mediated sacrificial protection strategy enhancing NiMo catalyst stability through in situ dendritic passivation. Zinc‐decorated NiMo on nickel felt (Zn‐NiMo/NF) exhibits considerable hydrogen evolution activity (94.6 mV overpotential at 50 mA cm−2) comparable to Pt/C. Under stringent load fluctuation cycling protocols (−500/50 mA cm−2), the zinc overlayer spontaneously reconstructs into laterally oriented, NiMo‐enriched dendrites providing dual protection: physical barriers suppressing dissolution (order‐of‐magnitude reductions in metal leaching) and sacrificial buffering wherein zinc preferentially oxidizes to zincate, shielding nickel from irreversible hydroxide formation. Zn‐NiMo/NF maintains stable performance while pristine NiMo/NF degrades substantially. Anion exchange membrane electrolyzer validation confirms minimal voltage escalation over 100 h cycling (1.645– 1.667 V), outperforming Pt/C (1.7028–1.857 V). This establishes sacrificial interface engineering as an effective paradigm for robust earth‐abundant electrocatalysts in renewable energy‐integrated hydrogen production. This study highlights the effectiveness of Zn-induced dendrite layers in enhancing the durability of NiMo HER catalysts under dynamic electrochemical conditions. Through in situ dendritic passivation, the Zn-NiMo catalyst preserves catalytic active sites and mitigates irreversible Ni oxidation/hydroxylation during repeated load fluctuation. ABSTRACT Integrating water electrolyzers with intermittent renewable energy poses critical durability challenges from dynamic load fluctuations inducing catalyst degradation. We report a zinc-mediated sacrificial protection strategy enhancing NiMo catalyst stability through in situ dendritic passivation. Zinc-decorated NiMo on nickel felt (Zn-NiMo/NF) exhibits considerable hydrogen evolution activity (94.6 mV overpotential at 50 mA cm −2 ) comparable to Pt/C. Under stringent load fluctuation cycling protocols (−500/50 mA cm −2 ), the zinc overlayer spontaneously reconstructs into laterally oriented, NiMo-enriched dendrites providing dual protection: physical barriers suppressing dissolution (order-of-magnitude reductions in metal leaching) and sacrificial buffering wherein zinc preferentially oxidizes to zincate, shielding nickel from irreversible hydroxide formation. Zn-NiMo/NF maintains stable performance while pristine NiMo/NF degrades substantially. Anion exchange membrane electrolyzer validation confirms minimal voltage escalation over 100 h cycling (1.645– 1.667 V), outperforming Pt/C (1.7028–1.857 V). This establishes sacrificial interface engineering as an effective paradigm for robust earth-abundant electrocatalysts in renewable energy-integrated hydrogen production. Advanced Science, EarlyView.