Both improving the intrinsic activity and activating basal plane sites of the layered metal dichalcogenides are desirable to enhance their electrocatalytic performance for energy storage and conversion. Herein, we present palladium (Pd)-doped tungsten disulfide (WS2) epitaxially sheathed around linear tungsten oxide for the hydrogen evolution reaction (HER). The Pd doping is evidenced to tune the electronic structure of WS2 for activating basal sites of WS2, while the unique core-shell structure facilitates charge transfer. The as-prepared Pd-WS2/W3O with 5.65 wt % Pd content exhibits a small overpotential of only 54 mV at -10 mA cm-2 and superior stability in the acidic electrolyte, which are superior to that of the 5 wt % Pt/C benchmark and are unprecedented in the reported WS2-based electrocatalysts. Theoretical results have revealed that Pd substituting for W in coordination with four S atoms is thermodynamically stable, and the in-plane S atoms adjacent to the doped Pd represent new catalytic active centers for promoting hydrogen adsorption. This work provides a new multiscale structural and electronic engineering strategy for improving the catalytic performance of transition-metal dichalcogenides.
Keywords: core/shell structure; electrocatalysis; hydrogen evolution reaction; tungsten oxide; tungsten sulfide.