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Abstract: The hydrogen storage capacities of π complex (Ti–η 2-(C2H2)) and the corresponding ethynyl metal hydrides (HC C–TiH) complex were tested using second order Møller Plesset method with 6-311++G(3df,3pd) basis sets. Both on Ti–η 2-(C2H2) and HC C–TiH, up to six hydrogen molecules can be absorbed with a binding energy of 0.20–0.42 eV/H2, corresponding the maximal retrievable hydrogen storage density of 14.06 wt%. A comparative study of various density functional theory calculations showed that the averaged H2 adsorption energy is not only considerably affected by the level of theory used but also dependent on the complex of the material dealing with. Dimerizations of the Ti–acetylene complexes were also discussed. [Copyright &y& Elsevier]

The structure and hydrogen adsorption properties of linear HC C-TMH (TM = Sc–Ni) complexes were systematically investigated using a density functional method. The ground states of the HC C-TMH (TM = Sc–Ni) complexes are 2, 3, 4, 3, 4, 3, 2, and 3. The gravimetric H 2 uptake capacities of these ground state HC C-TMH (TM = Sc–Ni) complexes are 4.54–14.56%. Ab initio molecular dynamic simulations indicated that maximal reversible hydrogen storage densities at 77–300 K of the ground state HC C-TMH (TM = Ti–Co) complexes are 6.65–12.00 wt%. The corresponding average adsorption energies are 0.07–0.49 eV. Due to reasonable superior storage capacity and ideal binding energy, HC C-TMH (TM = Ti–Co) complexes are proposed as a suitable hydrogen storage medium at ambient conditions. When HC C-TMH (TM = Ti, V, Cr) are nonground state structures, they can adsorb one more H 2 molecule than their ground states. Unfortunately, the first adsorbed H 2 molecules are dissociated and the adsorption energies are too large. Therefore, the importance of the multiplicity of sorbents for hydrogen storage is emphasized in this work. Image 1 • H 2 storage capacity of HC C-TMH(TM = Sc–Ni) is 4.54–14.56%. • All adsorbed H 2 molecules are in molecular form. • Reversible H 2 storage densities at 77–300 K of HC C-TMH (TM = Ti–Co) are 6.65–12.00%. • Importance of sorbent's multiplicity for H 2 storage study is shown. [ABSTRACT FROM AUTHOR]