Local bonding and atomic environments in Ni-catalyzed complex hydrides.
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 approximately 3 boron atoms with an interatomic distance of approximately 2.1 A and approximately 11 Ni atoms in a split shell at around 2.5 and 2.8 A. 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.
Graetz
J
J
Department of Energy Sciences and Technology, Brookhaven National Laboratory, Upton, NY 11973, USA.
Chaudhuri
S
S
Salguero
T T
TT
Vajo
J J
JJ
Meyer
M S
MS
Pinkerton
F E
FE
D001881:Borates / Q000737:chemistry*; D002384:Catalysis; D003198:Computer Simulation; D003460:Crystallization / Q000379:methods; D006859:Hydrogen / Q000737:chemistry*; D018020:Lithium Compounds / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008956:Models, Chemical; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D036103:Nanotechnology / Q000379:methods*; D009532:Nickel / Q000737:chemistry*; D010316:Particle Size; D013499:Surface Properties
D001881:Borates; D018020:Lithium Compounds; D046911:Macromolecular Substances; D009532:Nickel; D006859:Hydrogen; C021051:lithium borate