Dihydrogen in cation-substituted zeolites X - an inelastic neutron scattering study

Ramirez-Cuesta, A.J., Mitchell, P.C.H., Ross, D.K., Georgiev, P.A., Anderson, P.A., Langmi, H.W. and Book, D. (2007) Dihydrogen in cation-substituted zeolites X - an inelastic neutron scattering study. Journal of Materials Chemistry, 17 (24). pp. 2533-2539. ISSN 0959-9428 doi: 10.1039/b701167a

Abstract/Summary

An inelastic neutron scattering (INS) study of the rotational - vibrational spectrum of dihydrogen sorbed by zeolite X having substituted sodium, calcium and zinc cations is reported. The rotational - vibrational spectrum of H-2 was observed at low energy transfer ( below ca. 25 meV, 202 cm(-1)); the vibration was that of the H-2 molecule against the binding site (H-2 - X, not H - H). The vibration frequency was proportional to the polarising power of the cation (Na+ < Ca2+ < Zn2+). Polarisation of the H-2 molecule dominated the interaction of H-2 with this binding site. The total scattering intensity was proportional to the dihydrogen dose. However the vibrational intensities became constant at ca. 0.3 wt% showing that the H-2 binding sites had saturated. Additional dihydrogen appeared as unbound or weakly bound dihydrogen exhibiting recoil.