Nov 17, 2010

Computational study of silica-supported transition metal fragments for Kubas-type hydrogen storage

Journal of the American Chemical Society
Claire V J SkipperNikolas Kaltsoyannis

Abstract

To verify the role of the Kubas interaction in transition metal grafted mesoporous silicas, and to rationalize unusual rising enthalpy trends with surface coverage by hydrogen in these systems, computational studies have been performed. Thus, the interaction of H2 with the titanium centers in molecular models for experimentally characterized mesoporous silica-based H2 absorption materials has been studied quantum chemically using gradient corrected density functional theory. The interaction between the titanium and the H2 molecules is found to be of a synergic, Kubas type, and a maximum of four H2 molecules can be bound to each titanium, in good agreement with previous experiments. The average Ti-H2 interaction energies in molecules incorporating benzyl ancillary ligands (models of the experimental systems) increase as the number of bound H2 units increases from two to four, in agreement with the experimental observation that the H2 adsorption enthalpy increases as the number of adsorbed H2 molecules increases. The Ti-H2 interaction is shown to be greater when the titanium is bound to ancillary ligands, which are poor π-acceptors, and when the ancillary ligand causes the least steric hindrance to the metal. Extension of the tar...Continue Reading

  • References10
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Mentioned in this Paper

Chromium product (pharmacologic preparation)
Adsorption
Chemicals
Silica Measurement
Quantum
Ligands Activity
Fragments
Ligands
Chromium Measurement
Silicea terra homeopathic preparation

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