Nanonickel catalyst for kinetic destabilization of LiAlH4 (lithium alanate) for facile discharge of hydrogen

摘要

Microstructure and catalytic properties of new nanometric-scale Ni powders produced by a carbonyl nickel chemical vapour deposition process, have been investigated in respect to kinetic destabilization of LiAlH4 for hydrogen release during continuous heating conducted in a direct-power-compensation differential scanning calorimeter. The endothermic only heat flow was observed for the nanonickiel-catalyzed LiAlH4, which was prepared by short-time milling of 5 wt% nano-Ni with Li alanate. The endothermic heat that occurs around 160°C corresponds well to release 4.4 wt% H2 into a 1 bar reservoir, as determined in the Hiden Model IGA gravimetric gas analyzer. None of the three thermal events can be attributed to melting, and even 15 min milling resulted in receding of the melting peak at 170° C in the as-received LiAlH4. Therefore, nanonickel-catalyzed LiAlH4 desorbs hydrogen from solid crystal, without melting and with no exothermic desorption step reported in many previous studies. These results are discussed in terms of a catalytic promotion of thermodynamic destabilization that can occur in complex hydrides.