Double‐Site Ni–W Nanosheet for Best Alkaline HER Performance at High Current Density >500 mA cm−2

Abstract The efficiency of the alkaline hydrogen evolution reaction (HER) has remained limited. Herein, a bimetallic Ni–W catalyst fabricated by the rapid dehydration of W‐doped Ni(OH) 2 is reported. The Ni–W surface exhibits the following merits for an enhanced alkaline HER: a greater number of vacant outer d‐orbitals, better discharge characteristics, and a more significant difference in H adsorption between W and Ni atoms. The free water molecules are adsorbed onto W sites, then dissociated into *OH and *H. While *OH is released into the solution, *H is re‐adsorbed by nearby Ni sites. The synergistic effect of the Ni–W surface sites imparts this catalyst with the highest activity and the best stability at high current density. Specifically, at a current density of 500 mA cm ‐2 , the Ni–W catalyst reduces the overpotential to 303 mV, compared with 409 mV for the state‐of‐the‐art Pt/C catalyst. Additionally, the Ni–W catalyst exhibits better long‐term stability than the state‐of‐the‐art Pt/C. Whereas the Pt activity decreases by 181 mA cm ‐2 after 31 h of testing at 500 mA cm ‐2 , the Ni–W loses only 55 mA cm ‐2 under the same conditions. Density functional theory (DFT) calculations confirm the synergistic mechanism, which can be useful for general alkaline HER processes.