Transcript Nobel Methods for Generating Hydrogen Gas for Fuel Cells for ITS Applications

Development of Chemical Hydrogen Methods
for ITS Applications
Venkatram R. Mereddy
Department of Chemistry and Biochemistry
University of Minnesota Duluth
Possible Applications with Hydrogen Power
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There are many remote traffic signals on the road that don’t have access to
a power supply, so they use batteries that need to be changed often.
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The hydrogen based fuel cells can also be used as backup power source at
critical traffic signals, alternating-traffic signs, directional signals, speed-limit
signs, blinkers in series, and warning blinkers etc .
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The ability to store hydrogen at high volumetric and gravimetric density and
release it on demand is extremely important to the widespread
implementation of fuel cells as high power density portable systems.
Disadvantages with Cylinders as Source of Hydrogen
One major drawback that limits its utility is the use of compressed metal
cylinders as a source of hydrogen.
Limited volume (1.2 mass %), Generates limited electricity
Liquid hydrogen tank: requires lot of energy and low temperature keeping,
the energy utilization efficiency is low
The Advantages of Chemical Systems as Hydrogen Source
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Generation of large volumes of hydrogen gas with minimal amount of
chemical and not requiring frequent change of storage vessel
Production of electricity for longer duration of time
Spent chemicals can be regenerated back
By-product from the fuel cell is only water
Replacement of metal cylinders with compact chemical based hydrogen
storage vessel
Current Research Objectives
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The broad research objectives are to carry out detailed studies on the
development of chemical hydrogen storage materials for fuel cell derived
power generation for ITS related applications. The reason for evaluating
several different chemical hydrogen storage systems is to determine the
best chemical in terms of clean production of hydrogen, the ease of
recyclability and the overall cost benefits.
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The best chemical would be interfaced with fuel cell for ITS related
applications.
Boron Chemical Hydrides As Hydrogen Storage
Materials
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United States has the world’s largest reserves of borax, and boron based
hydrides can be prepared from it.
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Boron based hydrides offer an attractive solution to our quest in finding out
materials that are non-toxic, safe, compact, and readily provide large
quantities of hydrogen on demand and spent materials that could be easily
recycled.
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The notable boron hydrides that are actively being pursued are sodium
borohydride (SBH), lithium borohydride (LBH) and ammonia-borane (AB).
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However, studies have shown several limitations in terms of efficiency in
hydrogen generation and recycling of the spent materials.
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Hence there is a need to develop new materials that are easy to prepare,
readily generate hydrogen in a controlled way and efficiently recycled back
to complete the cycle for fuel cell.
Generation of Hydrogen from Borohydrides
Generation of Hydrogen from Borohydrides
Other Lewis Acids: Sc(OTf)3, FeCl3, CeCl3, MgCl2, ZnCl2, MnSO4, FeSO4, Ni(OAc)2
Lewis Acids supported on Charcoal: More controlled generation of hydrogen
Solid Borohydrides + Lewis Acids: hydrogen generation
Recycling of Borohydrides
Recycling of Borohydrides
Lithium Borohydride-Ammonia Complex (LBHA)
Lithium Amidoborane (LAB)
Solid Phase: LiNH2BH3 provides high storage capacity (10.9 wt% of hydrogen
at easily accessible dehydrogenation temperatures (~90 oC)
Liquid Phase: Catalytic procedure fast and hydrogen can be produced at low
temperatures
Guanidinium Borohydride (GBH)
• Thermal dehydrogenation was slow at 60 0C and required higher temperatures (> 150oC
• Metallo catalytic alcoholysis and hydrolysis is fast and complete
N2H4-BH3 & N2H4(BH3)2
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Hydrazine borane N2H4-BH3 (HB) and hydrazine bisborane N2H4(BH3)2
(HBB) contain15.37 wt % and 16.88 wt % of hydrogen, respectively.
Hydrazine sulfate or dihydrazine sulfate with sodium borohydride
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(N2H5)2SO4 + 2NaBH4 ----------N2H6SO4 + 2NaBH4 --------------N2H4BH3 + LiH --------------------
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Solid Phase Thermal (100 to 150 oC), Hydrogen generation
Liquid phase (alcohol, water): RT, low temperatures, metal catalysis
required for efficient hydrogen generation
2N2H4-BH3 + 2H2
N2H4(BH3)2 + 2H2
Li(N2H3BH3) + H2
Conclusions and Future Work
In conclusion we have carried out a detailed study on several boron
based chemicals on the generation of hydrogen
Thermal dehydrogenation studies have been performed in the solid
phase in the temperature range from 90o to 150 oC
Hydrogen generation studies have also been performed in the liquid
phase with alcohols and water at lower temperatures (rt and below)
Comparison of the above chemicals in terms of efficiency in hydrogen
generation, ease of recyclability, cost analysis and identification of the best
chemical for integration with fuel cell based electricity generation for ITS
applications.
Hydrazine bisborane N2H4(BH3)2 (HBB) contains 16.88 wt % of
hydrogen. This chemical would be utilized for hydrogen generation for fuel
cell based ITS applications.
Acknowledgements
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Professor Eil Kwon, University of Minnesota Duluth
Northland Advanced Transportation Systems Research Laboratories