Fig. 2. (A): (i) A top-down perspective of the MBene displays four distinct adsorption locations: top, bridge-1, hollow, and bridge-2 sites. (ii) A side-view schematic representation of the MBene is presented. (iii and iv) Diagrams illustrating the structures of Mo₂B₂O₂ and W₂B₂O₂ are shown, respectively. (B): Hydrogen coverage levels of 1/4 ML, 1/6 ML, and 1/9 ML are examined: (i) for W₂B₂O₂ and (ii) for Mo₂B₂O₂. (iii) The computed free energy (ΔG_H) for Mo₂B₂O₂ and (iv) for W₂B₂O₂ is presented, where the red, yellow, and blue lines correspond to hydrogen coverages of 1/9, 1/6, and 1/4, respectively. (C): (i and ii) A schematic illustration depicts the O-terminated MBene structure along with the alteration of the MBene surface through a single-metal adatom. (iii and iv) Three hydrogen adsorption locations (S0, S1, and S2) are identified, which correspond to the O atom adsorbed on the bridge-1 and bridge-2 sites, respectively. Reproduced with permission from ref. 53. Copyright 2020 American Chemical Society.