PMC

Calculated H-adsorption energy at different sites on M₂X monolayers: (a) one-side H-coverage and (b) two-side H-coverage.

The insets show the oxidized M₂X monolayers with H atoms at HC and TX sites, respectively.

The representative structures of (a) pristine M₂X and M₂X with both sides covered by atoms (red) at different positions: (b) HC, (c) TX, and (d) TM. By removing red atoms from one side of the monolayer, one-side coverage is realized.

Calculated overpotentials as a function of H-coverage on oxidized Mo₂X monolayers: (a) differential Gibbs free energy for H atoms adsorbed on HC sites, (b) average Gibbs free energy for H atoms adsorbed on HC sites, (c) differential Gibbs free energy for H atoms adsorbed on TX sites, (b) average Gibbs free energy for H atoms adsorbed on TX sites.

Calculated differential Gibbs free energy as a function of H-coverage on pure M₂X monolayers (M₂X-Ad) with H atoms adsorbed on: (a) HC, (c) TX, and (e) TM; Calculated average Gibbs free energy as a function of H-coverage on pure M₂X monolayers with H atoms adsorbed on: (b) HC, (d) TX, and (f) TM.

Calculated differential Gibbs free energy as a function of H-coverage on one-side hydrogenated M₂X monolayers (M₂XH-Ad) with H atoms adsorbed on: (a) HC, (c) TX, and (e) TM; Calculated average Gibbs free energy as a function of H-coverage on one-side hydrogenated M₂X monolayers with H atoms adsorbed on: (b) HC, (d) TX, and (f) TM.