Enhancement of hydrogen storage using functionalized MoSe₂/Graphene monolayer and bilayer systems: DFT study

Utilizing the spin-polarized density-functional theory (DFT), we present an investigation of the adsorption properties of hydrogen-gas molecules on ten different substrates, which are based upon defected and TM-doped MoSe₂ monolayer (ML) and MoSe₂/graphene bilayer (BL) systems (TM = Ni, Cu). Particularly, Ni, and Cu substitutional doping at Se site showed distinct high H₂ uptake capacity and thus to be good candidates for H₂ storage. On these latter catalysts, H₂ molecule exhibited physisorption with moderate respective energies E_ads = −0.307 and −0.362 eV, attributed to the enhancement in electric dipole moment and spin splitting (magnetism) induced in the substrate. The desorption processes of the H₂ molecule are found to cost energies of about 0.46 and 0.44 eV, respectively. Moreover, the H₂ molecule can move parallel to the substrate after crossing potential barriers of 0.56 and 0.65 eV, respectively. Furthermore, the gravimetric uptake density can further be improved by increasing the dopants concentrations. For instance, by increasing the number of Ni dopants from one to two atoms in the computational sample 4 × 4 PCs of MoSe₂ ML, the gravimetric density raises from 1.28 wt% to 3.6 wt% (almost triple). This should corroborate the candidacy of TM-doped @Se MoSe₂ for hydrogen storage applications. PAC Numbers: 31.15.E; 68.43.-h; 68.43.Mn; 68.65.Pq; 73.43.Cd; 75.70.Rf.