1 Hydrogen Storage Useful refs: See

Energy White Paper

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 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

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

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 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 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: There is, as yet, no material known to meet simultaneously all of these requirements

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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Carbon

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

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

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 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.