Hydrogen storage by stabilizing magnesium hydride in microparticles of silica aerogel Miriam Rueda a , Luis Miguel Sanz-Moral a , Ángel Martín *a , María José Cocero a a
www.hpp.uva.es
High Pressure Processes Group - Dpt. Chemical Engineering and Environmental Technology, University of Valladolid, Spain
[email protected]
HA.3
Introduction and Goals
1
The application of fuel cells using hydrogen as their energy source to vehicles or electronic equipment requires the development of new hydrogen storage devices. The simplest and most obvious storage solutions such as compressed gas bottles (G) or cryogenic tanks (L) have important limitations due to the physical properties of hydrogen. For this reason, magnesium hydride is proposed as one possible candidate due to its hight content in hydrogen (7,6%wt). Proposed approach
Limitations
MgH2 or
New solid state hydrogen storage: L
G
71 g/L
silica aerogel
SUPPORT: Microparticles of silica aerogel ENERGY SOURCE: Solid Magnesium (Boro)Hydride
14 g/L
MgBH4
Properties
Aims • Production of microparticles of hydrophilic/hydrophobic aerogel. • Encapsulation of two different precursors of Magnesium hydride or Borohydride (Magnesium Acetate and Magnesium Boride, respectively) in particles of silica aerogel
• High porosity • Surface area (~1000m2/g) • Low weight
Experimental set-up
2
1.Synthesis of microparticles of alcogel (sol-gel)
2. Synthesis of MgAc or MgB2 in silica alcogel
3. Production of precursor of Mg confined in aerogel co2
Tetramethoxysilane Methyltrimethoxysilane Hexane as dispersant Methanol
2.1
SC CO2 drying CO2 pump
MgAc in MeOH C=100mg/mL
4. Analysis of particles
P=110bar T=313K 4 cycles t=3.7h
Particle size distribution Dynamic Laser Scattering
PI
Morphology Scanning Electron Microscopy
Liquid vent
Hydrolysis
MgAc-alcogel in MeOH
1molTMOS:4.4molMeOH: 4molH2O:4.5mol hexane
Surface area BET
2.2
Structural properties FTIR and XRD
Hot air oven
CO2 buffer
TI
PI
MgB2 in THF C=25mg/mL
Extractor
Content of Mg Atomic absortion spectroscopy
NH4+/OH-
MgB2-alcogel in THF
Condensation O O
Recirculation pump
Hydrogenation-Dehydrogenation Sievert’ s PCT apparatus (converting the precursors into hydride)
Si O
O Si
O
O
O Si
t >10min
Removement of organic solvent Precipitation precursor
Si O
O
Aging 1 day in MeOH
MgAc-aerogel
MgB2-aerogel
Results and discussion
3 4
3.1. Microparticles of aerogel
3.2. Microparticles of precursor of Mg confined in aerogel MgB2 silica aerogel MgB2 in silica aerogel
Intensity
7
6
5
Volume(%)
4
3
MgB2 in aerogel ~15% MgB2 (8%Mg)
2 Hydrophobic aerogel 1
0,1
1
10
100
1000
20
30
1800
1600
50
60
70
80
90
1000
800
600
400
2θ (º)
1200
Si-O-Si CH3 asym
Mg n-H2 (T:1587,6)
4
1400
CO asym
Particle diameter(μm)
aBET(m2/g)
Vpore(cm3/g)
Dp(µm)
580
1
16-20
Surface area Volume of pores
40
Wavenumber(cm-1) 2000
Hydrophilic aerogel
0 0,01
10
Good properties as support to stabilize the precursor
Mg n-H2 (T:1431,9)
AcMg in aerogel hydrogenated AcMg in aerogel dehydrogenated 4th cycle AcMg in aerogel
AcMg in aerogel ~75% AcMg (8%Mg)
Conclusions
Aerogels are proposed as support to stabilize hydrides in their pores preserving their structure during cycles Different hydrophilic/hydrophobic aerogels are produced with ~8% Mg using two different precursors of MgH2: MgAc and MgB2 The presence of infiltrated precursor is confirmed by FTIR characterization for MgAc and XRD in the case of MgB2. The production of MgH2 from MgAc is also confirmed by FTIR analysis. ACKNOWLEDGMENTS: The authors thank the Spanish Ministry of Economy and Competitiveness through project ENE2011-24547 Miriam Rueda thanks the University of Valladolid for a FPI predoctoral grant and Pavia H2 Lab (University of Pavia) L.M. Sanz-Moral thanks the Spanish Ministry of Economy and Competitiveness for a FPI predoctoral grant Á. Martín thanks the Spanish Ministry of Economy and Competitiveness for a Ramón y Cajal research fellowship
5
OCO sym
OCO out of plane
Intensity
International Seminar on Aerogels Properties-Manufacture-Applications, 6-7th October 2014, Hamburg (Germany)
.
Si-O-Si
Si-O-Si
MgO
XRD confirms the presence of MgB2 in aerogel. In the case of MgAc, it is not possible to detect with this technique due to the amorphous structure. FTIR confirms the presence of the precursor AcMg in silica aerogel and the production of MgH2 after hydrogenation
Outlook
Measurement of the kinetics for hydrogenation and dehydrogenation reactions of the precursors Characterization of the samples after several hydrogenation and dehydrogenation cycles to confirm the preservation of the structure Tests with other precursors of hydrides or even mixing precursors
