Graphitic Nanofibres as Catalyst for Improving the Dehydrogenation Behavior of Complex Aluminium Hydrides

Abstract

In the present work, we explored the catalytic effect of graphitic nanofibres (GNF) particularly of two different morphology, namely planar graphitic nanofibre (PGNF) and helical graphitic nanofibre (HGNF) for enhancement of hydrogen desorption from complex aluminium hydrides such as LiAlH4 and LiMg(AlH4)3. We found that the catalytic activity of fibres depends mainly on its morphology. Hence helical morphology fibres possess superior catalytic activity than planar graphitic nanofibres. The desorption temperature for 8 mol% HGNF admixed LiAlH4 gets lowered from 159°C to 128°C with significantly faster kinetics. In 8 mol% HGNF admixed LiMg(AlH4)3 sample, the desorption temperature gets lowered from 105°C to ~70°C. The activation energy calculated for the first step decomposition of LiAlH4 admixed with 8 mol% HGNF is ~68 kJmol-1, whereas that for pristine LiAlH4 it is 107 kJ/mol. The activation energy calculated for as synthesized LiMg(AlH4)3 is ~66 kJ/mol. Since the first step decomposition of LiMg(AlH4)3 occurs during GNF admixing, the activation energy for initial step decomposition of GNF admixed LiMg(AlH4)3 could not be estimated. © 2010 18th World Hydrogen Energy Conference 2010, WHEC 2010, Proceedings. All Rights Reserved.