Continuous tuning of gas adsorption in two-dimensional transition metal disulfides enabled by vacancy engineering and high-entropy design

Understanding gas adsorption on defect-engineered two-dimensional (2D) materials is essential for advancing applications in energy storage, catalysis, and sensing. In this work, first-principles calculations are employed to systematically investigate the adsorption behaviors of H₂,0.28em0exO₂,0.28em0exH₂O,0.28em0exCO, and CO₂ at sulfur vacancy VS sites in both single-component transition metal dichalcogenides MS₂ (M = W, Mo, Ta, Nb, and V) and high-entropy (WMoTaNbV)S2 monolayers. In MS₂ systems, VS introduces localized defect states that enhance surface reactivity, leading to diverse adsorption modes including physisorption, chemisorption, and dissociative adsorption. Notably, H₂ dissociation is kinetically favorable on VS/TaS₂ and VS/NbS₂, while CO₂ remains weakly physiosorbed across all single-metal systems. In contrast, high-entropy (WMoTaNbV)S2 exhibits a continuous distribution of adsorption energies due to its diverse local coordination environments and synergistic multimetal interactions. This results in significantly reduced activation barriers for H₂ dissociation, enhanced adsorption strength for O₂,0.28em0exH₂O, and CO, and a transition of CO₂ adsorption from physisorption to chemisorption. Electronic structure analyses reveal that these improvements originate from multicenter d-p orbital hybridization and enhanced charge transfer at vacancy sites. Overall, the high-entropy design effectively tailors the adsorption landscape of 2D transition metal dichalcogenides, offering a promising strategy for developing advanced materials for hydrogen storage, CO₂ activation, and gas-sensing applications.