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Reaction pathways for hydrogen desorption from magnesium hydride/hydroxide composites: bulk and interface effects
F Leardini1, J R Ares, J Bodega
1Dpto. Fisica de Materiales, Universidad Autónoma de Madrid, 28049 Cantoblanco, Madrid, Spain. fabrice.leardini@uam.es
Physical Chemistry Chemical Physics : PCCP
|January 13, 2010
Summary
This study reveals new insights into magnesium hydride (MgH2) and magnesium hydroxide (Mg(OH)2) composite thermal desorption. Solid-state reactions significantly influence hydrogen release, offering pathways to enhance MgH2 performance.
Area of Science:
- Materials Science
- Chemical Engineering
- Solid-State Chemistry
Background:
- Magnesium hydride (MgH2) is a promising material for hydrogen storage.
- Understanding its thermal desorption behavior is crucial for practical applications.
- MgH2/Mg(OH)2 composites present complex desorption characteristics.
Purpose of the Study:
- To investigate the thermal desorption behavior of MgH2/Mg(OH)2 composites.
- To identify and characterize additional hydrogen (H2) desorption peaks.
- To elucidate the mechanisms governing H2 release from these composites.
Main Methods:
- Thermal Desorption Spectroscopy (TDS) was employed.
- Analysis of H2O and H2 desorption events.
- Investigation of solid-state reactions between MgH2 and Mg(OH)2.
Main Results:
- Two additional H2 desorption peaks were observed at lower temperatures than MgH2 decomposition.
- A low-temperature peak (~150°C) is attributed to H atom diffusion and reaction with surface OH groups.
- An intermediate-temperature peak (~350°C) results from an interface reaction between MgH2 and Mg(OH)2.
Conclusions:
- The onset of MgH2 decomposition is influenced by an incubation process involving catalytically active vacancies.
- Solid-state reactions within the composite significantly affect H2 desorption kinetics.
- Strategies for improving H2 desorption from MgH2 can be developed based on these findings.
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