Sub‐Nanometer Cobalt on Tungsten Titanium Carbide MXene (W ₂ TiC ₂ T _x ): An Electrocatalyst for Highly Efficient and Stable Alkaline Hydrogen Evolution at Industrial‐Scale Current Density

ABSTRACT Developing non‐precious electrocatalysts that simultaneously deliver high activity, long‐term durability, and industrial operability remains the critical challenge for the alkaline hydrogen evolution reaction (HER). Herein, a structurally well‐defined two‐dimensional metal carbide MXene, tungsten titanium carbide (W 2 TiC 2 T x ), is synthesized for the first time via the W 2 TiAlC 2 MAX‐phase precursor. Cobalt loading combined with rational modulation of local atomic configurations and metal–support interactions (MSI) enables the construction of a highly active and robust Co/W 2 TiC 2 HER catalyst. The optimized Co/W 2 TiC 2 ‐700 exhibits small overpotentials of 63 and 191 mV at 10 and 100 mA cm − 2 , and outstanding long‐term durability of over 1000 h stable hydrogen production at 4000 mA cm − 2 . In a flow‐cell MEA electrolyzer, Co/W 2 TiC 2 delivers near‐unity hydrogen Faradaic efficiency across a wide current range (50–400 mA cm − 2 ) while requiring significantly lower cell voltages than commercial Pt/C. Quasi‐in‐situ XPS, XANES, and EXAFS analyses reveal that thermal modulation induces the transformation of Co from isolated atoms and large nanoparticles into uniform sub‐nanometer particles anchored on the outer tungsten layers. DFT calculations identify Co–W interfacial sites as the primary active centers. This work highlights the critical role of rational design and utilization of MSI in MXene‐supported catalysts for electrochemical water splitting.