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

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 (Delta G(H)*) and the inter-Ag distance, where the Ag-d6.38 (the initial distances of 6.38 A between two Ag atoms doped in the MoS2 lattice) electrocatalyst with a Delta G(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.