Hydrogen storage properties of nanoconfined LiBH 4 –NaBH 4

Abstract

Eutectic melting compositeCarbon dioxide activation Cyclic stability a b s t r a c tIn this study a eutectic melting composite of 0.62LiBH 4 e0.38NaBH 4 has been infiltrated in two nanoporous resorcinol formaldehyde carbon aerogel scaffolds with similar pore sizes (37 and 38 nm) but different BET surface areas (690 and 2358 m 2 /g) and pore volumes (1.03 and 2.64 mL/g). This investigation clearly shows decreased temperature of hydrogen desorption, and improved cycling stability during hydrogen release and uptake of bulk 0.62LiBH 4 e0.38NaBH 4 when nanoconfined into carbon nanopores. The hydrogen desorption temperature of bulk 0.62LiBH 4 e0.38NaBH 4 is reduced by~107 C with the presence of carbon, although a minor kinetic variation is observed between the two carbon scaffolds.This corresponds to apparent activation energies, E A , of 139 kJ mol À1 (bulk) and 116 e118 kJ mol À1 (with carbon aerogel). Bulk 0.62LiBH 4 e0.38NaBH 4 has poor reversibility during continuous hydrogen release and uptake cycling, maintaining 22% H 2 capacity after four hydrogen desorptions (1.6 wt.% H 2 ). In contrast, nanoconfinement into the high surface area carbon aerogel scaffold significantly stabilizes the hydrogen storage capacity, maintaining~70% of the initial capacity after four cycles (4.3 wt.% H 2 ).

Hydrogen Desorption Properties of Bulk and Nanoconfined LiBH4-NaAlH4

“…The temperature of the maximum hydrogen release rate of the mixed (T = 356˝C) and melt infiltrated samples (T = 364˝C) occur at significantly reduced temperatures (∆T~130˝C) as compared to that of bulk LiBH 4 -NaAlH 4 (T = 496˝C). This effect has previously been reported for other nanoconfined binary hydride systems that showed a reduction in the temperature of the maximum hydrogen release rate compared to bulk, e.g., LiBH 4 -Mg(BH 4 ) 2 (∆T max~´6 0˝C), LiBH 4 -Ca(BH 4 ) 2 (∆T max~´9 5˝C) and LiBH 4 -NaBH 4 (∆T max~´1 07˝C) [33][34][35].…”

Review of magnesium hydride-based materials: development and optimisation

“…By increasing the surface-to-bulk atomic ratio, changes in the thermodynamics are foreseen. However, handling nanoparticles of metals or hydrides is very challenging and this is commonly done using a porous scaffold to stabilise the particles and to prevent them from coalescence [66].…”

Reactive Hydride Composite of Mg2NiH4 with Borohydrides Eutectic Mixtures

“…A full rehydrogenation has not been obtained because of the limited H 2 pressure applied in the experimental conditions. As for previous studied mixtures [27][28][29][30][31], a hydrogen pressure of 100 bar is expected to fully rehydrogenate the systems. The nanoconfinement of the studied mixtures into a nanoporous scaffold to obtain nanostructured materials [13,15,19,20,[22][23][24][25]31,32] might be explored to improve the thermodynamics and kinetics of hydrogen sorption reactions and cyclability.…”