Adsorption of atomic hydrogen on monolayer MoS2

The adsorption of atomic hydrogen on monolayer MoS2 has been intensively studied, but the ground-state adsorption configuration remains controversial. In this study, we investigate the adsorption properties of atomic hydrogen on monolayer MoS2 systematically using first-principles density functional theory calculations. We considered all the previously proposed adsorption sites, S-top, bridge, and hollow sites. Among them, S-top is the most energetically preferred, with a tilted S-H bond. Its calculated adsorption energy is -0.72 eV. The next lowest-energy configuration is that the H atom is located at the hollow site; the adsorption energy is slightly higher than the former, by 0.22 eV. The tilting of the S-H bond contributes to the adsorption energy up to -0.29 eV, a factor unrecognized in previous first-principles studies. These results account for the discrepancy in theory. Besides, the effects of spin-polarization also change the relative energetics of possible adsorption configurations.