LAUSR

Alloying of transition metal dichalcogenides (TMDs) is a pioneering method for engineering electronic structures with expanded applications. In this study, MoSe2–VSe2–NbSe2 ternary alloy nanosheets are synthesized via a colloidal reaction. The composition is successfully tuned over a wide range to adjust the 2H–1T phase transition. The alloy nanosheets consist of miscible atomic structures at all compositions, which is distinct from immiscible binary alloys. Compared to each binary alloy, the ternary alloys display higher electrocatalytic activity toward the hydrogen evolution reaction (HER) in an acidic electrolyte. The HER performance exhibits a volcano‐type composition dependence, which is correlated with the experimental d‐band center (εd). Spin‐polarized density functional theory (DFT) calculations consistently predict the homogenous atomic distributions. The Gibbs free energy of H adsorption (ΔGH*) and the activation barrier (Ea) support that miscible ternary alloying greatly enhances the HER performance.