1. 1 Hydrogen Storage Useful refs: See http://people.bath.ac.uk/cestjm/Shared/DTC/ch50182-Mays-Day2/

2. Energy White Paper

3. 3 Why Hydrogen for Energy? 2H 2 + O 2 = 2H 2 O + Energy Three Major Attractions (1) Clean combustion of a non-toxic fuel (2) Delivered energy / mass is very high (energy gain / electron best of all the chemical elements) (3) Offers greatest potential for “Sustainable Energy Future”

4. 4 Economic recyclable/rechargeable vessels Near ambient temperature pressure operation High hydrogen storage capacity/small volume Fast recharge and discharge kinetics Impact Safety Tolerant to trace poisoning Hydrogen Storage Systems for Mobile Applications

5. On a weight basis H 2 has nearly three times the energy content of gasoline. – 120 MJ/kg vs. 44 MJ/kg (LHV) On a volume basis the situation is reversed. – 3 MJ/L (5000 psi), 8 MJ/L (LH 2 ) vs. 32 MJ/L Physical storage of hydrogen is bulky. Capacity of reversible chemical storage at useful T, P is low. Other challenging issues include energy efficiency, cost, and safety. Storing enough hydrogen on vehicles to achieve greater than 300 miles driving range is difficult. On-Board Hydrogen Storage Challenge JoAnn Milliken, US DOE Status Report, 22 Oct 2002

6. 6 Leachman’s EOS for Normal Hydrogen Leachman, et al. J Phys Chem Ref Data 38 (2009) 721

7. 7 Cryogenic Storage of Hydrogen Spherical designs best S/V 3% / day boil off (@ 20 K) Insulation bulky 40% liquefaction penalty High pressure options Liq H 2 Liq N 2 Steel/ Aluminium Low emmittance multilayers

8. 8 Compression Storage of Hydrogen Composite H 2 Cylinder – 12 wt% Conformable geometrics Higher wt% via increased pressure Heating on filling H 2 : 350 bar Glass/Carbon fibre Aluminium/Thermoplastic

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11. 11 Advanced Materials for Hydrogen-Storage: 3 Strategic Challenges I.Storage Capacity ≥ 6.5 wt% II.Reversibility of thermal absorption / desorption cycles (at an accessible temperature) III.Low cost, low toxicity, low risk of explosion, etc. (Source: www.doe.gov) There is, as yet, no material known to meet simultaneously all of these requirements

12. 12 Volume of 4 kg of hydrogen compacted in different ways, with size relative to the size of a car. Mg 2 NiH 4 LaNi 5 H 6 H 2 (liquid)H 2 (200 bar) Schlapbach and Züttel, Nature, 15 Nov 2001

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14. Carbon

15. 15 Reversibly stored amount of hydrogen on various carbon materials versus the specific surface area of the samples. Louis Schlapbach & Andreas Züttel, Nature 414, 15 Nov 2001 = nanotube samples (best-fit line indicated) = other nanostructured carbon samples

16. 16 Magnesium-based Storage Materials Problems associated with magnesium: Stability of the MgH 2. Surface oxidation of magnesium based powders. Slow diffusion of hydrogen through MgH 2. Possible Solutions: Milling to develop a nanocrystalline material. Introduction of catalysts to dissociate hydrogen by co-milling or by developing multilayers. Alloying with other metals such as Ni, Al etc….

17. 17 Conclusions Mobile Carbon Nanotubes - Less than 0.5 wt% uptake at RT. Adsorption related to surface area. - There may be a means of creating high hydrogen storage capacity CNT, but despite a large global effort, it remains elusive and lacking independent verification. Milled Magnesium + Alloys - Continuing to optimise milling conditions / PGM additions, in an effort to produce a practical on-board auto hydrogen store. - Operating Temperature still a problem

18. 18 Low-cost storage material Able to scale up storage solution to large-scale? Relatively high hydrogen storage capacity Reasonably fast recharge and discharge kinetics Tolerant to trace poisoning Long-term cycling Hydrogen Storage Systems for Stationary Applications

19. 19 zeolite A zeolites X and Y zeolite RHO. The corners on each framework represent Si or Al and these are linked by oxygen bridges represented by the lines on the frameworks Zeolite Framework Structures

20. 20 Zeolite A – Si-Al network. Zeolite Preparation Hydrothermal Procedure Ion exchange using metal nitrate Characterisation XRD SEM with EDX BET surface area (N 2 at 77K)

21. 21 Hydrogen uptake in Zeolites -196°C 15bar H 2

22. 22 Wt% Hydrogen plotted against BET surface area for activated carbon and zeolites samples.

23. 23 Conclusions Stationary Activated Carbon Significant amounts of hydrogen can be stored reversibly (up to 4wt%) at 77 K and 15 bar. Zeolites - Up to 2wt% at 77 K and 15 bar. - Hydrogen storage capacity of certain zeolites can be increased by manipulation of the zeolite exchangeable cations, e.g. Zeolite RHO Unfortunately, at room temperature storage properties are below 1wt%, for both activated carbon and zeolites.

24. 24 THE STORAGE OF HYDROGEN IN SOLIDS Carbon : A deeper understanding of the unique interaction between H 2 (H) and carbon; – nature of physi-, vs chemi-sorption, in nanostructured carbon – the role of dangling bonds. Light Hydrides : A deeper understanding of the thermodynamics and kinetics of decomposition / absorption reactions and (intermediate) processes; – metallicity, chemical reactivity and electronic states, – innovation in the synthesis and stabilisation (handling) of hydrides. Nanostructured Porous Solids : The tailoring of pore geometry, and (interior) chemical reactivity for hydrogen activation, storage and release; – the interaction between H 2 (H) and porous solids.