Author/Authors :
Graetz, J Brookhaven National Laboratory - Department of Energy Sciences and Technology, USA , Chaudhuri, S Washington State University - Applied Sciences Laboratory and Institute for Shock Physics, USA , Salguero, T T HRL Laboratories, LLC., USA , Vajo, J J HRL Laboratories, LLC., USA , Meyer, M S General Motors Research and Development Center - Materials and Processes Lab, USA , Pinkerton, F E
Abstract :
The local bonding and atomic environments in the Ni-catalyzed destabilized system LiBH4/MgH2 and the quaternary borohydride-amide phase Li3BN2H8, were studied by x-ray absorption spectroscopy. In both cases the Ni catalyst was introduced as NiCl2 and a qualitative comparison of the Ni K-edge near-edge structure suggests the Ni2+ is reduced to primarily Ni0 after ball milling. The extended fine structure of the Ni K edge indicates that the Ni is coordinated by ~3 boron atoms with an interatomic distance of approximately 2.1 Å and ~11 Ni atoms in a split shell at around 2.5 and 2.8 Å. These results, and the lack of long-range order, suggest that the Ni is present as a disordered nanocluster with a local structure similar to that of Ni3B. In the fully hydrogenated phase of LiBH4/MgH2 a small amount Mg2NiHx was also present. Surface calculations performed using density functional theory suggest that the lowest kinetic barrier for H2 chemisorption occurs on the Ni3B(100) surface
