Development of Chemical Hydrogen Methods for ITS Applications

1. Development of Chemical Hydrogen Methods for ITS Applications Venkatram R. Mereddy Department of Chemistry and Biochemistry University of Minnesota Duluth

2. Possible Applications with Hydrogen Power • 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. • 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 . • 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.

3. 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 • 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

4. Current Research Objectives • 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. • The best chemical would be interfaced with fuel cell for ITS related applications.

5. Boron Chemical Hydrides As Hydrogen Storage Materials • United States has the world’s largest reserves of borax, and boron based hydrides can be prepared from it. • 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. • The notable boron hydrides that are actively being pursued are sodium borohydride (SBH), lithium borohydride (LBH) and ammonia-borane (AB). • However, studies have shown several limitations in terms of efficiency in hydrogen generation and recycling of the spent materials. • 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.

6. Generation of Hydrogen from Borohydrides

7. 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

8. Recycling of Borohydrides

9. Recycling of Borohydrides

10. Lithium Borohydride-Ammonia Complex (LBHA) Lithium Amidoborane (LAB) • Solid Phase: LiNH2BH3 provides high storage capacity (10.9 wt% of hydrogen at easily accessible dehydrogenationtemperatures (~90 oC) • Liquid Phase: Catalytic procedure fast and hydrogen can be produced at low temperatures

11. Guanidinium Borohydride (GBH) • Thermal dehydrogenation was slow at 60 0C and required higher temperatures (> 150oC • Metallo catalytic alcoholysis and hydrolysis is fast and complete

12. N2H4-BH3 & N2H4(BH3)2 • 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 • (N2H5)2SO4 + 2NaBH4 ----------- 2N2H4-BH3 + 2H2 • N2H6SO4 + 2NaBH4 --------------- N2H4(BH3)2 + 2H2 • N2H4BH3 + LiH -------------------- Li(N2H3BH3) + H2 • Solid Phase Thermal (100 to 150 oC), Hydrogen generation • Liquid phase (alcohol, water): RT, low temperatures, metal catalysis required for efficient hydrogen generation

13. 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.

14. Acknowledgements • Professor Eil Kwon, University of Minnesota Duluth • Northland Advanced Transportation Systems Research Laboratories