posters 5th Asia-Pacific NMR Symposium 2013

Multinuclear NMR Characterization of Nano-confined Hydrogen Storage Materials (#192)

Aditya Rawal 1 , James M Hook 1 , Meganne Christian 2 , Kondo-Francois Aguey-Zinsou 2
  1. UNSW Mark Wainwright Analytical Centre, Kensington, NSW, Australia
  2. Merlin Group, ARC Centre for Functional Nanomaterials, School of Chemical Engineering, , UNSW , Sydney, NSW, Australia

Sodium borohydride (NaBH4) is a promising material for hydrogen storage, with a hydrogen storage capacity of ~10 mass %. However, it exhibits poor characteristics in terms of its reversibility and the high temperatures and pressures required for hydrogen adsorption/ desorption. Recently, it was shown that by synthesizing NaBH4 particles of <30 nm, significantly reduced temperatures and pressures for the hydrogen adsorption and desorption could be achieved. Additionally, encapsulating the NaBH4 particle in a nickel shell enabled nano-confinment of the molten NaBH4 during hydrogen desorption which promoted reversibility, fast adsorption-desorption kinetics and yielded a net hydrogen storage capacity of ~5 mass %. 1

Insights into the structure of the as-synthesized, NaBH4 (Ni), with hydrogen desorbed and resorbed, were revealed by solid state 1H, 11B and 23Na NMR spectroscopy. 1D 1H and 11B NMR spectra yielded quantitative information about the extent of hydrogen adsorption and desorption as well as showing the presence and evolution of multiple borohydride species in the materials. 2D 11B{1H} heteronuclear correlation experiments readily identified the nature of the different borohydride species. In complementary experiments, multiple sodium sites were detected by 2D 23Na MQMAS experiments, while 23Na{1H} NMR correlation experiments probed the proximities of the sodium species with respect to the borohydride moieties. Finally, 1H spin diffusion measurements confirmed that the different borohydride species formed during repeated hydrogen adsorption-desorption cycles were maintained within nanometer scale proximity by the nickel shell.

  1. Meganne L. Christian and Kondo-François Aguey-Zinsou, Core–Shell Strategy Leading to High Reversible Hydrogen Storage Capacity for NaBH4, ACS Nano, 2012, 6 (9), pp 7739–7751