Influence of composition–phase interplay on the electrochemical activity of ternary transition metal dichalcogenides

Alloying is a powerful strategy to tailor the electronic structures of 2D transition metal dichalcogenides. Controlling the functionalities is essential to explore the full potential of these ternary nanosheets with tunable electronic properties. Here, Nb was successfully alloyed with W to form ternary Nb_xW_1−xS₂ nanosheets with different stoichiometric ratios via colloidal hot-injection synthesis. Incorporation of Nb alters the band structure of parent WS₂, allowing for controlled tuning of electronic properties. High resolution transmission electron microscopy reveals an irregular atomic arrangement at higher Nb concentrations, with a notable transition from the pure 2H phase to a mixed 2H–1T′ phase at a controlled concentration of Nb content in the composition. Nb induces a shift of the Fermi level, causing a transition from semiconducting to metallic nature in ternary nanosheets, which facilitates enhanced electrocatalytic activity for the hydrogen evolution reaction (HER) of Nb_0.5W_0.5S₂ compared to pristine WS₂.