Hydrogen desorption and absorption for activated magnesium hydride

The interaction between MgH2 and LiBH4 was studied to determine the resultant effects on hydrogen desorption and absorption kinetics for potential use as a hydrogen storage material. It is found that the addition of LiBH4 in small molar ratios results in improved kinetics of the same order as those observed for mechanically milled magnesium. The mixture of MgH2 + LiBH4 in ratios at and below 4:1, once reacted, is a highly reversible material at 300°C and it is observed that the kinetics improve upon the process of hydrogen cycling. This improvement is partially attributed to a refinement in microstructure that results in highly porous particle agglomerates and it is this feature that is likely to have a large effect on the kinetics of hydrogenation due to the rate limiting step of the reaction being hydrogen diffusion into the particles of Mg which can be coated in MgH2 phase, through which H2 does not diffuse easily. Additionally it is observed via Raman spectroscopy that a new bonding structure exists in the H2 cycled mixture after desorption which might improve the rehydrogenation of the sample and reduce the enthalpy of decomposition through an intermediate reaction pathway.

Name dc:type.qualificationname

d_ph

Level dc:type.qualificationlevel

d_ph

Grantor dc:publisher.institution

University of Birmingham

Year dc:date.issued

2010

Author dc:creator

• Prendergast, James W.

• QD Chemistry