Nuclear Magnetic Resonance Study of Molecular Dynamics in Ammine Metal Borohydride Sr(BH₄)₂(NH₃)₂

TY - JOUR

T1 - Nuclear Magnetic Resonance Study of Molecular Dynamics in Ammine Metal Borohydride Sr(BH4)2(NH3)2

AU - Gradišek, Anton

AU - Jepsen, Lars H.

AU - Jensen, Torben R.

AU - Conradi, Mark S.

PY - 2016

Y1 - 2016

N2 - We investigated molecular dynamics in Sr(BH4)2(NH3)2, which is a representative compound for a series of ammine metal borohydrides, a novel family of systems exhibiting promising hydrogen storage properties with high hydrogen content and low decomposition temperature. Two types of hydrogen-containing groups present, namely, BH4 and NH3, prompt the investigation whether these materials differ from other borohydrides from a molecular dynamics point of view. The investigation was performed using 1H and 11B NMR spectroscopy and spin-lattice relaxation techniques. Different thermally activated reorientational processes of BH4 tetrahedra about their 2- and 3-fold symmetry axes were identified from temperature-dependent spin-lattice relaxation rates for both nuclei, and the corresponding activation energies were obtained. In addition, a selectively deuterated compound was studied to further distinguish the dynamic processes between both hydrogen-containing groups. Our study presents physical insight into the dynamic properties of Sr(BH4)2(NH3)2 on a microscopic level of atomic groups, providing a link between the microscopic and bulk properties of this material. (Graph Presented).

AB - We investigated molecular dynamics in Sr(BH4)2(NH3)2, which is a representative compound for a series of ammine metal borohydrides, a novel family of systems exhibiting promising hydrogen storage properties with high hydrogen content and low decomposition temperature. Two types of hydrogen-containing groups present, namely, BH4 and NH3, prompt the investigation whether these materials differ from other borohydrides from a molecular dynamics point of view. The investigation was performed using 1H and 11B NMR spectroscopy and spin-lattice relaxation techniques. Different thermally activated reorientational processes of BH4 tetrahedra about their 2- and 3-fold symmetry axes were identified from temperature-dependent spin-lattice relaxation rates for both nuclei, and the corresponding activation energies were obtained. In addition, a selectively deuterated compound was studied to further distinguish the dynamic processes between both hydrogen-containing groups. Our study presents physical insight into the dynamic properties of Sr(BH4)2(NH3)2 on a microscopic level of atomic groups, providing a link between the microscopic and bulk properties of this material. (Graph Presented).

U2 - 10.1021/acs.jpcc.6b08162

DO - 10.1021/acs.jpcc.6b08162

M3 - Journal article

AN - SCOPUS:84994645714

SN - 1932-7447

VL - 120

SP - 24646

EP - 24654

JO - The Journal of Physical Chemistry Part C: Nanomaterials, Interfaces and Hard Matter

JF - The Journal of Physical Chemistry Part C: Nanomaterials, Interfaces and Hard Matter

IS - 43

ER -