Distance synergy of single Ag atoms doped MoS2 for hydrogen evolution electrocatalysis

Highlights: • A general distance synergy of single Ag atoms doped MoS₂ in catalyzing HER was presented. • A volcanic trend between ΔG_H* and the inter-Ag distance was found. • The optimum HER activity with the minimum ΔG_H* of 0.03 eV is at the neighboting in-plane S sites. • A proper inter-Ag distance could moderately alter the charge of the S atoms adjacent to the Ag atoms. Doping heteroatoms into the 2D MoS₂ lattice provides an opportunity for regulating the electronic structures of the MoS₂ basal plane and further activating the inert in-plane S atoms for efficient hydrogen evolution reaction (HER). However, the most appropriate type and distribution of the doping atoms in MoS₂ induced the optimum HER performance remains a big challenge. Herein, through the density functional theory calculations, we present a general distance synergy of single Ag atoms doped MoS₂ in catalyzing HER, resulting in the optimum HER activity at the in-plane S sites neighbored to and between the Ag atoms. A general distance synergy between the doped Ag atoms in modifying the HER reactivity of in-plane S atoms adjacent to the Ag atoms is found via the control of the distance between the Ag atoms. This distance synergy shows a volcanic trend between the adsorption free energy of hydrogen (ΔG_H*) and the inter-Ag distance, where the Ag_d6.38 (the initial distances of 6.38 Å between two Ag atoms doped in the MoS₂ lattice) electrocatalyst with a ΔG_H* value of 0.03 eV locates at the top of the volcano. Moreover, the stability and HER catalytic mechanism of the Ag_d6.38 electrocatalyst as well as the doping density of Ag atoms in MoS₂ are discussed. This investigation offers useful guidance for the experimental groups to trigger the activity of the MoS₂ basal plane by precisely controlling the distance between the doped heteroatoms.