1T-MoS2 monolayer doped with isolated Ni atoms as highly active hydrogen evolution catalysts: A density functional study

Abstract

The 1T phase of transition metal dichalcogenides (TMDs) has been shown to be catalytically active during the hydrogen evolution reaction (HER). However, the catalytic performance is greatly affected by the extent of surface coverage by H, due to the non-optimal bonding strength between H and the 1T-MoS2 surface. In this work, the density functional theory was employed to predict a novel catalyst Ni-doped-1T-MoS2 of HER. The improved performance of 1T-MoS2 was believed to come from the change of the bond strength between S and H atoms, which is tailoring by the doping of transition metal Ni. More importantly, in contrast to undoped 1T-MoS2, the excellent catalytic performance of Ni-doped 1T-MoS2 is only minimally affected by the extent of coverage by H. Based on density of states, crystal orbital Hamiltonian population and Bader charge analyses, this enhanced performance is attributed to the weakening of the S to H bond strength, which is conducive to H desorption. Based on an implicit solvation model, the catalytic activity of Ni-doped 1T-MoS2 was also found to be less vulnerable to the presence of water. These findings are expected to facilitate the future design of single-atom electrocatalysts with high efficiency for the HER.