V ₂ CT _x MXene as a Sacrificial Promoter for NiFe Catalyst for Anion Exchange Membrane Electrolyzers

ABSTRACT Nickel‐iron layered double hydroxides (NiFe‐LDH) show excellent activity, their poor conductivity limits practical implementation in electrolysers. Previous reports have shown that combining nickel‐iron layered double hydroxide (NiFe‐LDH) materials with MXenes significantly increases the oxygen evolution reaction (OER) activity, however, the rationale behind this is not clear. Herein, we report operando X‐ray absorption spectroscopy (XAS) of V ₂ CT _x MXene‐enhanced NiFe‐LDH catalysts, revealing important insights into MXene‐hydroxide synergy. Operando X‐ray absorption reveals a two‐step vanadium transformation: V ₂ CT _x initially oxidizes during hydrothermal synthesis, acting as a reducing agent that promotes ordered Fe ₂ NiO ₄ formation, then undergoes further oxidation under OER conditions, to form mixed‐valence V ³⁺ / ⁴⁺ / ⁵⁺ oxide species that establish transient electronic coupling with NiFe active sites. Finally, the NiFe@V ₂ CT _x composites were tested in an Anion Exchange Membrane (AEM) electrolyzer over 144 h of continuous operation at 500 and 1000 mA cm ⁻² , with NF25 achieving degradation rates as low as 0.76 mV h ⁻¹ at 1000 mA cm ⁻² . Postmortem tests reveal that V ₂ CT _x undergoes progressive dissolution during operation, yet the structurally modified NiFe electrodes retain superior activity relative to the unmodified reference throughout the full test duration. These findings demonstrate that V ₂ CT _x functions beyond passive conductive support as an active electronic participant whose structural legacy sustains durable performance even after vanadium leaching.