First-principles study of H₂ adsorption mechanism on defective MoSe₂/graphene heterostructures

Recently, as a promising energy carrier, hydrogen attracted intensive research interest. In the present work, the spin-polarized density-functional theory (DFT) is applied to investigate the adsorption of hydrogen-gas molecules on six different adsorbents: (1) MoSe₂ monolayer (ML) with single vacancy of Mo; (2) Mn-doped MoSe₂ ML at either Mo or Se site; (3) MoSe₂:V_Mo/graphene heterostructure; and (4) MoSe₂:Mn/graphene heterostructure. MoSe₂:V_Mo/graphene heterostructure showed the highest adsorption energy of − 0.41 eV, but H₂ molecule exhibits chemisorption associated with dissociation which qualify it for gas sensing applications. MoSe₂:Mn doping Se site stands prone to be the best candidate for H₂ storage. The energy adsorption of H₂ molecule on top of Mn site is E _ads = − 0.28 eV. The desorption is shown to cost an energy of about 0.36 eV. Furthermore, the uptake capacity can further be enhanced by increasing the doping concentration of Mn (e.g., MoSe₂:2Mn@2Se was tested and found to reach 2.9% wt). Graphical abstract: [Figure not available: see fulltext.].