The hydrogen storage capacity of Sc atoms decorated porous boron fullerene B40: A DFT study

The hydrogen storage capacity of transition metal Sc atoms decorated porous boron fullerene B40 is investigated by the pseudopotential density functional method. The B-40 cage contains two B-40 cavities (diameter: 3.36 angstrom) and four B-7 holes (diameter: 3.68 angstrom). It is calculated that the structures with the Sc atom outside the hollow sites of these cavities are the most stable. The calculated binding energy of the Sc atom to the B-6 and B-7 cavities on the surface of B-40 are 4.61 and 5.24 eV, much larger than the experimental cohesive energy of bulk Sc (3.90 eV/atom). Moreover, the distance between the neighboring two Sc atoms (5.61 angstrom) is considerably larger than that of the Sc-2 dimer (3.20 angstrom), therefore, the problem of Sc atoms aggregative to form the Sc-n cluster is expected to be overcome. The average adsorption energies and consecutive adsorption energies reveal that each Sc atom can most adsorb five H-2 molecules. The calculated average hydrogen adsorption energies per H-2 for B-40(Sc-5H(2))(6) (n = 1-5) are in the energy range from 0.33 to 0.58 eV, which is suitable for hydrogen storage under near-ambient conditions. The Dewar Kubas interaction dominates the adsorption of H-2 by B(40)Sc6. The calculated desorption temperature and molecular dynamic simulation indicate that the B-40(Sc-5H(2))(6) structure is easy to desorb H-2 molecules. The HGD of the bulk [B-40(Sc-5H(2))(4)](4). is 6.18 wt%, a little smaller than that for B-40(Sc-5H(2))(6) (8.3%), however still exceeding the 5.5 wt% at 2017 specified by the US department of energy (DOE). Therefore, the stable Bo structure decorated by the Sc atoms can be applied as one candidate for hydrogen storage materials under near-ambient conditions. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.