Wednesday 10 July 2013, Strathblane & Cromdale Halls, 16:30-18:30
Poster session B - Hydrogen storage and other host-guest systems
P.102 Investigation of hydrogen distribution in storage tanks using neutrons
S Börries, P K Pranzas, M Dornheim, O Metz, J Bellosta von Colbe, T Klassen and A Schreyer
Helmholtz-Zentrum Geesthacht, Germany
Hydrogen is a very promising energy carrier for the future, especially for mobile applications. It can be stored safely
and reversibly at high volumetric densities in hydrogen storage tanks filled with nanocrystalline light metal hydrides.
Due to the sensitivity of neutrons towards hydrogen, Neutron Radiography (NR) is the ideal technique for in situ
investigations in order to directly observe the hydrogenation behaviour of the metal hydride powder inside the tank
under operating conditions. First-time in situ NR measurements of hydrogen storage tanks using fission neutrons
were successfully performed at the instrument NECTAR at FRM II. Several thermodynamic parameters were
measured in parallel, enabling a quantitative investigation of the hydrogen distribution inside the tank. The results
confirm previous studies using thermal neutrons [1,2]. The quantitative evaluation revealed a huge influence of
temperature gradients and material structure on the hydrogen sorption behaviour. In this way the results allow
design and optimization of hydrogen storage tanks in respect to efficiency and safety.
[1]
[2]
P.K. Pranzas et al., Advanced Engineering Materials 13 (2011), 730
J.M. Bellosta von Colbe et al., International Journal of Hydrogen Energy 37 (2012), 2807
P.103 Hydrogenation mechanism in Pt/Pd-infiltrated Na-X zeolites at ambient temperature
Y N Choi1, H Lee1, K B Yoon2 and J H Seo3
1
Korea Atomic Energy Research Institute, Korea, 2Sogang University, Korea, 3Korea Basic Science Institute, Korea
Zeolites, which belong to typical nano-porous framework materials, have been intensively studied for their useful
applications as catalysts and gas adsorbents. Na-X is an aluminosilicate framework material, belongs to Faujasite
class, having appropriate sodium ions as charge balancers. Platinum and palladium nano-clusters were infiltrated
into the supercage (diameter 11 Å) by a reduction method. Transmission electron microscopy was employed to
characterize the nano-scale morphology of the samples. Physical and chemical properties of those samples, NaX:Pt and Na-X:Pd, before and after the hydrogen exposure were investigated by PCT(sorption isotherm), in-situ
neutron scattering, in-situ electron spin resonance, and ex-situ x-ray photoelectron spectroscopy measurements.
Experimental evidences on the hydrogenation occurred at ambient temperature and possible model of its
mechanism will be discussed.
P.104 Hydrogen-storage materials in nanoporous substrates studied through incoherent inelastic neutron scattering
D Colognesi1, L Ulivi1, M Fichtner2, Z Zhao-Karger2, A Javier Ramirez-Cuesta3 and A Orecchini4
1
ISC - CNR, Italy, 2Karlsruhe Institute of Technology, Germany, 3STFC Rutherford Appleton Laboratory, UK, 4Institut
Laue-Langevin, France
Incoherent inelastic neutron scattering measurements on three impregnated/infiltrated composites of hydrides
(namely, NaAlH4, LiBH4+Mg(BH4)2 and MgH2) and nanoporous scaffolds (i.e. active carbon fibres) have been
performed at low temperature. After a careful data analysis, these experimental results have been compared to the
corresponding spectroscopic data of bulk hydrides. Evident signatures induced by infiltration process on the NaAlH4
phonon bands have been detected, showing up as a strong peak broadening and smoothing together with, in some
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cases, an energy shift. Less pronounced, but still visible, phonon spectrum modifications have been found in MgH2,
mainly concentrated in the low-energy spectral region. Finally, no relevant effect has been observed for
LiBH4+Mg(BH4)2.
P.105 Neutron diffraction and DFT modelling investigations of a porous metal-organic framework for CO2 separation
S Duyker1, V K Peterson1, M R Hill2, S R Batten3 and D R Turner3
1
Australian Nuclear Science and Technology Organisation, Australia, 2CSIRO Materials Science & Engineering,
Australia, 3Monash University, Australia
Intense research is currently directed towards realising Metal-Organic Frameworks (MOFs) for industrially-applied
gas separation and storage due to their unique structural properties, including: robustness; thermal and chemical
stability; unprecedented internal surface area; and high void volume. A particular focus of current research is the
development of MOFs for the separation of CO2 from the other components of flue gas from fossil-fuelled power
plants.
One new material of interest is Cu3(cdm)4 (cdm = carbamoyldicyanomethanide), a porous MOF with a high density
of coordinatively unsaturated Cu centres, and exceptional adsorption selectivity for CO2 over N2 and H2. Using
neutron powder diffraction on Wombat, the high intensity instrument at OPAL, with progressive in situ dosing of CO 2
into the framework, we explore the arrangement of the host framework and guest CO2 molecules, gaining insight into
the nature of the host-guest interaction and the host’s response to the guest. DFT-based molecular dynamics
simulations of the host-guest system help to further clarify the locations and relative energies of the adsorption
sites. The information obtained on the nature of the CO2 binding may assist with the future rational design of the
next generation of MOFs for gas separations.
In addition to the structures of the guest-loaded framework, using variable-temperature measurements we explore
the influence of adsorbed guest species on the material’s unusual thermal expansion behaviour.
P.106 Probing the hydrogen sorption mechanism in 1:1 LiNH2-MgH2 by Powder Neutron Diffraction; the role of
magnesium imide and non-stoichiometry
T Hoang and D Gregory
University of Glasgow, UK
The 1:1 LiNH2-MgH2 system possesses a gravimetric density of 8.19 wt% of H2 and a volumetric capacity of 100
kg/m3 H2. The amide-hydride composite can begin to release hydrogen under relatively mild conditions when ballmilled. Prior to hydrogen release, a solid state metathesis reaction occurs between the binary components in the
mill. Sufficient ball-milling times enhance the hydrogen desorption kinetics and suppress the evolution of ammonia
in the subsequent thermal dehydrogenation of the composite system. The overall process of dehydrogenation,
however, remains unclear and different mechanisms have been proposed by several research groups. This system
has been investigated systematically in our group. Our results suggest the existence of a cubic imide phase, MgNH,
as a key intermediate phase in the dehydrogenation process. Quantitative phase information vs. milling time is
determined from powder neutron diffraction data. The evolution of LiH(D) is detected and the structure of cubic
MgNH(D) is elucidated. A rational reaction mechanism is proposed on the basis of PND characterization of partly
dehydrogenated intermediate phases.
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P.107 Hydrogen Motion in LiBH4
W Lohstroh and L Silvi
Technische Universität München, Germany
LiBH4 is discussed intensely as potential hydrogen storage material due to its high gravimetric and volumetric
hydrogen storage density of 18.4 mass% H2 and 121.3 kg/m3, respectively. However, its slow sorption kinetics and
the temperatures required for hydrogen exchange are major obstacles for applications. In LiBH 4, hydrogen is bonded
covalently to a central B atom and the BH4 complex bonds ionically to Li+. In our study, we used quasi-elastic
neutron scattering to further elucidate the hydrogen motion as a function of temperature in the low temperature
(LT)- phase and across the structural phase transition of LiBH4 to the high temperature (HT) phase at 380 K. The
experiments have been done at direct time-of-flight spectrometer TOFTOF at the FRM2 and the elastic inelastic
structure factor (EISF) could be determined for a Q-range up to 4 Å-1. The large dynamical range is essential for the
discrimination of different kind of rotational modes. At temperatures well below the structural phase transition, 120
deg jump rotations occur around the C3 symmetry axis of the BH4- units. As the phase transition is approached the
dynamics of the BH4 unit changes continuously. At in intermediate state, a tumbling motion of the tetrahedron is
observed while at 413 K the hydrogen motion is best described as a free rotation on a sphere. The results confirm
that the structural phase transition is closely linked with the dynamics of the BH4 units.
P.108 Switchable magnetism in a porous coordination polymer
R Mole1, M Nadeem2, J Stride2, V Peterson1 and P Wood3
1
Bragg Institute, Australia 2University of New South Wales, Australia, 3University of Cambridge, UK
The preparation of new materials with combined properties is a fundamental challenge in materials chemistry. One
possible combination for such a multifunctional material is that of porosity, which has applications in areas such as
gas storage and catalysis, and ferromagnetic ordering. If the occupation of the pore could be shown to have an
effect on the magnetic ordering, such a material would have potential uses as sensor. We have previously reported
the magnetic structures of the porous coordination polymer Co3(OH)2(C4O4)2.3H2O [1]. This revealed a complex
behaviour with three different predominantly antiferromagnetic ordered phases that are a result of the inherent
magnetic frustration associated with the crystal structure and the single ion anisotropy that stems from the orbitally
degenerate octahedral Co2+ ion. Further work [2] has suggested that this material undergoes a transition from an
antiferromagnetic structure to a ferromagnetic structure upon dehydration. After reviewing the magnetic properties
and structures of the hydrated phase, I will describe the results of recent neutron diffraction experiments [3] that
show a complex, series of magnetic structures for the dehydrated compound Co3(OH)2(C4O4)2 and confirm the
observation of a net magnetic moment. The origin of this switchable behaviour is thought to be driven by small
changes in the local crystal field about the cobalt centres.
[1]
[2]
[3]
R.A. Mole, et. al Inorg. Chem. 2011, 50, 2246.
M. Kurmoo, et. al, Chem. Commun. 2005, 3012.
R.A. Mole et. al. Submitted to Inorg. Chem. 2013
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P.109 The liquid structure of ammonia borane in water and dimethyl sulphoxide
A Nathanson1, T Headen2, N Skipper1 and A Soper3
1
University College London, UK, 2Cella Energy UK, 3STFC, UK
Ammonia borane (AB) is a promising hydrogen storage material due to is high releasable hydrogen content (13.06
wt%), stability in air and relatively mild conditions needed for hydrogen release. It is a prime candidate material to
improve upon high pressure hydrogen gas as the automotive fuel source of the future. Solvation in water or other
polar solvents converts this solid into a liquid fuel, whilst this decreases its hydrogen content, it makes the fuel
easier and more familiar to handle. Also, the solubility and stability of ammonia borane in a number of solvents
allows easy processing into novel forms that can improve its dehydrogenation properties [Kurban. et al. J. Phys.
Chem. C. 2010, 114, 21201–21213]. Understanding the structure within these solutions allows further
optimisation and understanding of these processes. On a more fundamental level AB contains both protic and
hydridic hydrogen atoms, forming dihydrogen bonds in the solid state, therefore a thorough understanding of its
structure in the solution state in a protic (water) and aprotic (Dimethyl sulfoxide) solvents is of great interest. Recent
data from the SANDALS beamline at ISIS of ammonia borane in water and dimethyl sulphoxide has used isotopic
substitution and Empirical Potential Structure Refinement (EPSR) to gain and insight into the full 6-dimensional
position and orientation structure of these solutions. We show that the solutions are well mixed and observe an
unusual three dimensional structure due to the solvation shell arrangement around the dual natured ammonia
borane molecule.
P.110 QENS study of the 2-dimensional motion of ammonia in CaC6
A Nathanson1, N Skipper1, C Howard1, J Edge1 and F Fernandez-Alonso2
1
University College London, UK, 2STFC, UK
Ternary metal ammonia graphite intercalation compounds (GICs) have potential applications as a superconductors,
hydrogen storage materials and battery electrodes. Knowledge of the inplane structure and motion of the
intercalates is essential for predicting behaviour under various conditions. We present data from the IRIS beam line
at ISIS on the two dimensional confined motion of liquid ammonia in a multi staged calcium ammonia GIC. The
movement of ammonia was followed between 2 and 300K with quasi elastic neutron scattering (QENS) using the
high incoherent scattering of the protons. We observed a three modes of motion, diffusion, following the ChudleyElliot model, at >200K, rotation, between 200 and 100K and a still frozen structure below 100K. Additionally, this
work has enabled precise determination of the interlayer spacing of a variety of stages of the calcium ammonia GIC
and shown ammoniation to be only partially reversible at 300K.
P.111 In situ neutron diffraction investigation of carbon dioxide adsorption in ordered mesoporous silica
A Sapalidis1, F Katsaros1, K Stefanopoulos1, D Bowron2 and T Steriotis1
1
National Centre for Scientific Research "Demokritos", Greece, 2ISIS Neutron Source, STFC Rutherford Appleton
Laboratory, UK
Sorption of fluids on nanoporous solids is very important in a series of applications such as catalysis, H 2 and natural
gas upgrade and storage, membrane separations etc. These processes are very complex as the properties of sorbed
fluids are in many cases different from the bulk due to confinement. In addition, in case of mesoporous materials,
during the early stages of adsorption the pore filling proceeds via the formation of an adsorbed film. As the
adsorption progresses the film grows in thickness until a sharp increase of the adsorbed amount occurs due to
capillary condensation. In the present study, the confinement of carbon dioxide within the pores of ordered
mesoporous silica (SBA-15) was studied by adsorption from the gas phase with in situ neutron diffraction, with the
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aid of a high-pressure adsorption apparatus. The experiment was carried out at the Near and InterMediate Range
Order Diffractometer (NIMROD, at ISIS, Rutherford Appleton Laboratory, UK). The main advantage of NIMROD is that
it bridges the gap between conventional small-angle and wide-angle neutron scattering (optimised Q-range: 0.02Å1≤ Q ≤50Å-1). The neutron measurements have been performed alongside a CO2 adsorption isotherm (T=253 K) in
the pressure range 0-20 bar. Both the adsorption mechanism and the structural characteristics of the confined
carbon dioxide molecules are investigated.
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