A Hybrid Hydrogen Storage System Based on Hollow Glass Microspheres

1. A Hybrid Hydrogen Storage SystemBased on Hollow Glass Microspheres C. Eisenmennger-Sittner1 and G. H. S. Drexler-Schmid2, 1 Vienna University of Technology, Institute of Solid State Physics, Vienna, Austria 2 Austrian Institute of Technology, Vienna, Austria • INTRODUCTION • A COMBINED STORAGE SYSTEM • COATING SMALL FRAGILE OBJECTS • CATALYTIC REACTION AND REPEATED USE • REQUIREMENTS FOR PRESSURIZATION • CONCLUSION AND FUTURE ASPECTS VAASSCAA 9, Sydney, August 13 – 16, 2018

2. Conventional hydrogen storage techniques: INTRODUCTION Carbon fibre, Lincoln composites • Compressed hydrogen (4.8 wt%) • Liquid hydrogen (high storage density) Opel Zafira LH2-tank • Low temperature adsorption (6.5 wt%) • Chemical and material based - hydrides metal hydrides 2-5 wt% chemical hydrides 10-15 wt% Universtiy of Bayreuth) VAASSCAA 9, Sydney, August 13 – 16, 2018

3. Do we need these massive tanks? A synergy of three approaches A COMBINED STORAGE SYSTEM Hydrogen Compression Chemical Hydrides Natural hydro-gen carrier H H O aka water Hydrolysis, 8 hydrogen/reaction VAASSCAA 9, Sydney, August 13 – 16, 2018

4. 1 µm 45 µm THE AMAZING GLASS MICROSPHERES s = 6 GPa = 300 bar VAASSCAA 9, Sydney, August 13 – 16, 2018

5. Yield strength of soda lime glass s = 6 GPa LOADING PRESSURE ESTIMATE Calculation of maximum loading pressure pmax Boiler formula: d … wall thickness, 1 µm r … sphere radius, 20 µm pmax = 6 kbar (!) Glass Microspheres can act as tiny hydrogen tanks as they can bear pressures well comparable to macroscopic tanks. In addition they are cheap and safe. VAASSCAA 9, Sydney, August 13 – 16, 2018

6. Hydrogen can be LOADED into hollow glass microspheres by diffusion of H2 into the sphere at high pressure (approx. 30-70 MPa) and high temperature (approx. 200°C): HYDROGEN LOADING high outside pressure (500-700 bar) high outside temperature (200 °C) H2 45 µm VAASSCAA 9, Sydney, August 13 – 16, 2018

7. The compressed hydrogen can be STORED in hollow glass microspheres at room temperature because of the low permeability of the glass shell. HYDROGEN STORAGE Ambient conditions H2 45 µm VAASSCAA 9, Sydney, August 13 – 16, 2018

8. Hydrogen can be RELEASED from the microspheres by thermally activated diffusion at elevated temperature. HYDROGEN RELEASE 45 µm VAASSCAA 9, Sydney, August 13 – 16, 2018

9. what about chemical heat? MICROSPHERE BASED STORAGE SYSTEM S. Sherif, D. Yogi Goswami, E. K. Stefanakos and A. Steinfeld, Handbook of Hydrogen Energy, Boca Ratonn 2014 VAASSCAA 9, Sydney, August 13 – 16, 2018

10. The hydrolytic reaction EXAMINING THE HYDROLYTIC REACTION is strongly exothermal with Q = 217 kJ/Mol = 3900 kJ/kg (molar mass of reactants: 56 g/mol) following Q = m·c·DT with 10 g of reactant one can heat 1l of water (c = 4,2 kJ/(kgK)) by DT = 9 K The hydrolytic reaction is an efficient heat source ! VAASSCAA 9, Sydney, August 13 – 16, 2018

11. Water The exothermic reaction can be facilitated by a catalyst deposited onto the sphere. This gets the heat right to where it is needed, i. e. the surface of the sphere. CATALYTIC ENHANCEMENT Catalyst VAASSCAA 9, Sydney, August 13 – 16, 2018

12. released hydrogen hydrolytic re- action produces heat water; may gradually be supplied HYBRIDE STORAGE SYSTEM catalyst coated microspheres, hydrogen loaded G. Schmid PhD Thesis, TU Vienna, 2015 VAASSCAA 9, Sydney, August 13 – 16, 2018

13. ITEMS NEEDED ü • Glass microspheres ü • Catalyst material ü • Coating method ü • Evaluation of efficiency of hydrolysis D • Pressurization of coated spheres D • Evaluation of total system performance VAASSCAA 9, Sydney, August 13 – 16, 2018

14. Metals (oxide support) CATALYST Chosen Catalyst Pt or Ru noble metal TiO2 as support material anatase rutile brookite (Dirk Rosenthal 2007) • Different TiO2 phases • Anatase most promising VAASSCAA 9, Sydney, August 13 – 16, 2018

15. Non-reactive or reactive magnetron sputtering as process of choice • Platinum, Ruthenium COATING METHOD Inert, high melting point metals • Titanium Oxides Stable, high melting point oxides • Requirement posed by substrate Relatively low deposition temperature, smaller than softening point of borosilicte glass (approx. 400°C) Particle containment and intermixing necessary VAASSCAA 9, Sydney, August 13 – 16, 2018

16. Efficient intermixing is paramount COATING SMALL FRAGILE OBECTS Rotation and concussion! Mixing bowl Deposition setup 200 mm Motion profile VAASSCAA 9, Sydney, August 13 – 16, 2018

17. COATED SPHERES uncoated 100 µm target target coated with catalyst 45° VAASSCAA 9, Sydney, August 13 – 16, 2018

18. CATALYTIC REACTION - ESTIMATES Experimental Conditions: • 85 mMol NaBH4 • Q=217 kJ/Mol Results in: • Maximum hydrogen yield at RT: approx. 2.1 l • Maximum temperature rise: DT = approx. 84 K mi … masses of water, hydrogen and glass ci … specific heats of water, hydrogen, glass VAASSCAA 9, Sydney, August 13 – 16, 2018

19. Experimental setup EVALUATION OF CATALYTIC PROPERTIES Typical results DT time to reach maximum DT, tmax VAASSCAA 9, Sydney, August 13 – 16, 2018

20. CATALYSTS AND COATING ARCHITECTURE Different Catalysts Different Coating Architecture Sample 1: 0.2 nm Ti/0.2 nm Ru Sample 2: 0.2 nm TiO2/0.2 nm Ru Sample 3: 0.2 nm TiO2/ 0.5 nm+ TiO2+Ru Sample 4: 0.6 nm TiO2àTi/ 0.5 nm Ru VAASSCAA 9, Sydney, August 13 – 16, 2018

21. REPEATED USE – ACTIVATION PROCEDURE • Take spheres from concluded catalysis experiment. • Start reactivation procedure as soon as possible. • Rinse spheres in distilled water. Perform at least • two rinsing runs. • Set pH value, which is alcaline after catalysis, to • neutral by rinsing in diluted hydrochloric acid. • Rinse again in distilled watrwe ro get rid of • acidic residues. VAASSCAA 9, Sydney, August 13 – 16, 2018

22. Temperature rise REPEATED USE Selected coating system Hydrogen yield VAASSCAA 9, Sydney, August 13 – 16, 2018

23. REPEATED USE - DEGRADATION Significant degradation is clearly visible despite on- going catalytic activity after 4 runs. VAASSCAA 9, Sydney, August 13 – 16, 2018

24. REQUIREMENTS FOR PRESSURIZATION • Hydrogen pressure and external temperature Microspheres should be pressurized at pressures as high as possible, i. e. approx. 600 bar. Filling temperatures should ensure rapid permeation without glass softening, i. e. approx. 300°C. • Coating system stability The system of adhesion promoter/catalyst support has to withstand the pressurization conditions and has to leave the permeability of the spheres unaltered. This has not been checked yet! VAASSCAA 9, Sydney, August 13 – 16, 2018

25. Approproiate glass brands should be chosen for long time storage. REQUIREMENTS FOR STORAGE p0 … loading pressure C … decay constant VAASSCAA 9, Sydney, August 13 – 16, 2018

26. Basics of a hybride H-storage system CONCLUSION AND FUTURE ASPECTS The basic ingredients of a hybride hydrogen storage system combining chemical storage and storage in pressurized glass microspheres could be manufactured. • Catalytic performance The theoretical limits of the hydrolytic reaction of sodium borohydride with water could be reached in respect to hydrogen yield and reaction temperture. • Total system performance The total system performace has to be tested on pressurized coated microspheres. The influence of the coating on hydrogen loading and release has to be evaluated. VAASSCAA 9, Sydney, August 13 – 16, 2018

27. ACKNOWLEDGEMENTS This work was financially supported by the Austrian Science Fund, Grants P-19379, P-22718, TRP-6 and TRP-281 VAASSCAA 9, Sydney, August 13 – 16, 2018