Improved reversible dehydrogenation of 2LiBH 4 +MgH 2 system by introducing Ni nanoparticles
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Zaiping Guoa) Institute for Superconducting and Electronic Materials, University of Wollongong, Wollongong, New South Wales 2522, Australia; and School of Mechanical, Materials & Mechatronics Engineering, University of Wollongong, Wollongong, New South Wales 2522, Australia
Xuebin Yub) Institute for Superconducting and Electronic Materials, University of Wollongong, New South Wales 2522, Australia; and Department of Materials Science, Fudan University, Shanghai 200433, China
Huakun Liu Institute for Superconducting and Electronic Materials, University of Wollongong, Wollongong, New South Wales 2522, Australia (Received 29 November 2010; accepted 3 March 2011)
We report that the hydrogen de/resorption of the 2LiBH4+MgH2 system was modified by introducing Ni nanoparticles. Dehydrogenation analysis revealed that the first-step dehydrogenation, i.e., the decomposition of MgH2, can be significantly promoted by adding a small amount of Ni because of the catalytic effect. However, the improvement of the second-step dehydrogenation, corresponding to the decomposition of LiBH4, needs the addition of a large amount of Ni, resulting in the formation of a Mg–Ni–B ternary alloy. Furthermore, the presence of the Mg–Ni–B ternary alloy allowed an increased reversible H-capacity, in which about 5.3 wt% of hydrogen can be rehydrogenated under 400 °C and 55 bar hydrogen pressure over 10 h, which is higher than that of the pristine 2LiBH4+MgH2 system (4.4 wt%).
I. INTRODUCTION
Along with the increasing demands for cleaner and more environmentally friendly energy, the use of hydrogen as an energy carrier has attracted significant interest because no pollutants are produced when it is burned or used in fuel cells.1 However, the challenges to the efficient and safe storage of hydrogen have to be overcome before the widespread use of hydrogen as an energy carrier is possible. Storing hydrogen in metal hydrides is very attractive, as they can offer higher volumetric hydrogen densities than compressed hydrogen gas or liquid hydrogen, without using very high pressure containment vessels or cryogenic tanks.2 A system target of 5.5 wt% hydrogen for automobile fuelling has been set by the U.S. Department of Energy for 2015.3 Because the transition metallic hydrides cannot store adequate amounts of hydrogen, interest has focused more recently on lightweight element complex hydrides such as alanates (AlH4),4–6 amides (NH2),7,8 and borohydrides (BH4).9,10 Address all correspondence to these authors. e-mail: [email protected] b) e-mail: [email protected] DOI: 10.1557/jmr.2011.72
a)
J. Mater. Res., Vol. 26, No. 9, May 14, 2011
LiBH4 has a high theoretical hydrogen capacity of 18.5 wt%. It was first reported in 1940 by Schlesinger and Brown, and used to be considered as a powerful reducing agent in organic chemistry.11 Since the important study of LiBH4 as a hydrogen storage material by Züttel et al. in 2002,9 various investigations, in such areas as structural analysis, study of dehydrogenation/rehydrogenation behaviours, etc., have been unde
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