Mirror-Symmetric Nanoarray Networks of Atomic Ni-Incorporated Tungsten Oxynitride for Efficient and Robust Alkaline...

The development of alkali-efficient hydrogen evolution reaction (HER) electrocatalysts is essential for future deployment of anion-exchange membrane water electrolysis technology. Herein, we report a novel heteroatom-induced strategy to construct the mirror-symmetric nanoarray networks of Ni-doped WO₃ on carbon cloth and design a corresponding new type of atomic Ni-incorporated tungsten oxynitride (Ni-WNO) electrocatalyst for alkaline HER. Impressively, the Ni-WNO shows high activity (-35 mV at -10 mA cm^-2), small Tafel slope (32 mV dec^-1) and excellent stability (>1200 h at -1.0 A cm^-2), representing the best-performing W-based electrocatalyst for alkaline HER. Multiple spectroscopy characterizations reveal that Ni-WNO is highly active for adsorbing aggressive OH^-/H₂O groups, resulting in the in situ formation of lattice hydroxyl (i.e., W-OH) species with Brønsted acidity, which, we disclose for the first time, can serve as a mediator to alter the generation of metal-H intermediates from a conventional sequential to a concerted proton-electron transfer (CPET) pathway, thus breaking the pH-dependent limitations in proton-deficient alkalies. Further isotope experiments demonstrate that the surface-mediated H-H coupling can be feasibly accelerated on atomic W-Ni units, thereby enabling Ni-WNO catalyzing alkaline HER via a new kinetically fast CPET-Tafel pathway.