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A Protocol for Safe Lithiation Reactions Using Organolithium Reagents
Published on: November 12, 2016
Stability and reversibility of LiBH4.
Philippe Mauron1, Florian Buchter, Oliver Friedrichs
1EMPA Materials Sciences and Technology, Department of Mobility, Environment and Energy, Division of Hydrogen and Energy, Uberlandstrasse 129, 8600 Dübendorf, Switzerland. philippe.mauron@empa.ch
The Journal of Physical Chemistry. B
|December 20, 2007
Summary
Lithium borohydride (LiBH4) shows potential as a hydrogen storage material due to its high hydrogen density. However, its reversibility requires high temperatures and pressures, impacting practical applications.
Area of Science:
- Materials Science
- Chemical Engineering
- Hydrogen Storage Technologies
Background:
- Lithium borohydride (LiBH4) is a complex hydride with a high gravimetric hydrogen density (18.5 wt%).
- Its potential for mobile applications necessitates understanding its stability and hydrogen release/reuptake characteristics.
Purpose of the Study:
- To investigate the stability of LiBH4 under varying conditions.
- To determine the thermodynamic parameters for hydrogen desorption.
- To assess the reversibility of the hydrogen storage reaction.
Main Methods:
- Pressure, concentration, and temperature (pcT) measurements under constant hydrogen flow.
- Extrapolation of pcT data to equilibrium conditions.
- Thermodynamic analysis using the van 't Hoff equation.
- X-ray diffraction (XRD) for material characterization.
- Temperature-programmed desorption (TPD) to quantify hydrogen release.
Main Results:
- Thermodynamic parameters for LiBH4 desorption: enthalpy of reaction (DeltarH) = 74 kJ/mol H2 and entropy of reaction (DeltarS) = 115 J/K mol H2.
- LiBH4 decomposes to LiH + B + 3/2H2, theoretically releasing 13.9 wt% hydrogen.
- Reversible reaction achieved at 600°C and 155 bar.
- XRD confirmed LiBH4 formation.
- TPD showed 8.3 wt% hydrogen desorbed from rehydrided material versus 10.9 wt% in the first dehydrogenation.
Conclusions:
- LiBH4 exhibits promising hydrogen storage capacity but requires extreme conditions for reversible hydrogen cycling.
- The observed decrease in hydrogen release upon rehydration suggests degradation or incomplete reversibility.
- Further research is needed to improve the reversibility and operating conditions for practical LiBH4-based hydrogen storage.
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