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Hydrogen absorption kinetics of the transition-metal-chloride-enhanced NaAlH system

Journal of Physical Chemistry C, ISSN: 1932-7447, Vol: 116, Issue: 27, Page: 14205-14217
2012
  • 29
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  • 15
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Metrics Details

  • Citations
    29
    • Citation Indexes
      29
  • Captures
    15

Article Description

This study elucidates the role of transition metal (TM) additives in enhancing hydrogen (H) reversibility and hydrogenation kinetics for the NaAlH system. The isothermal hydrogen absorption kinetics of the planetary milled (PM) NaAlH + xTMCl (TM row 1 = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu; row 2 = Zn, Y, Zr, Nb, Mo, Ru, Rh Pd; row 3 = Pt; 2 < n < 5) and cryo-milled (CM) NaAlH + xTMCl (TM row 1 = Ti, V, Cr, Fe, Co, Ni, Cu; 2 < n < 3) systems have been measured at 140 °C and 150 bar system pressure. The variation in hydrogenation kinetics across the TM series for NaAlH + xTMCl is strongly dependent on the TM species and additive level, milling technique, and the type, structure, and morphological arrangement of nanoscopic Al TM phases that are embedded on the NaAlH surface. In the most interesting case, the surface-embedded Al Ti phases in the TiCl -enhanced NaAlH system perform a dual catalytic function, where the outer Al Ti surface performs dissociation/recombination of molecular H and the inner Al Ti surface allows the distortion of a minor number of Al-H bonds from AlH tetrahedra in the vicinity of the subsurface Al Ti /NaAlH interface. The density of Ti atoms in the subsurface interface (which is Al:Ti composition- and H cycling temperature-dependent) shows the strongest effects on hydrogenation kinetics. © 2012 American Chemical Society.

Bibliographic Details

Mark P. Pitt; Magnus H. Sørby; Bjørn C. Hauback; Per E. Vullum; John C. Walmsley; Randi Holmestad; Mark Paskevicius; Craig E. Buckley; Hermann Emerich

American Chemical Society (ACS)

Materials Science; Energy; Chemistry

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