Comparative WS₂-NbS₂ and MoS₂-NbS₂ Binary Alloy Nanosheets as Excellent Hydrogen Evolution Reaction Electrocatalysts

The electronic structures of 2D transition metal dichalcogenides (TMDs) can be modulated by alloying, enhancing their catalytic properties and broadening applications. In this study, binary alloy nanosheets-W_{1- x}Nb_xS₂ and Mo_{1- x}Nb_xS₂-were synthesized via colloidal reactions, achieving homogeneous atomic mixing across the full composition range, which surpasses selenide alloy mixing. Nb incorporation into WS₂ or MoS₂ nanosheets produces a more metallic phase, and density functional theory calculations confirm both the high degree of atomic mixing and the metallic character of the alloys. For the hydrogen evolution reaction (HER) in acidic electrolytes, these alloys exhibit enhanced catalytic activity when the Nb composition x is between 0.2 and 0.5, outperforming x = 0 and 1. Gibbs free energy calculations for hydrogen adsorption show that the metal and S atoms in the alloys become catalytically active, directly correlating with the improved HER performance. These findings offer valuable insight into how atomic-scale alloying modulates the catalytic activity of TMDs for next-generation catalytic applications.