Solid-state Hydrogen Storage, Hydrogen Separation Membranes, Permanent Magnets, Hydrogen Embrittlement.
Hydrogen is widely regarded as the most promising alternative to carbon-based fuels: it can be produced from a variety of renewable resources, and - when coupled with fuel cells - offers near-zero emissions of pollutants and greenhouse gases. However, developing hydrogen as a major energy carrier, will require solutions to many scientific and technological challenges.
Solid-state Hydrogen Storage
One challenge is to how to effectively store hydrogen on vehicles. Conventional storage solutions include liquefaction or compression, however there are energy efficiency and major safety concerns associated with both these options. Therefore, there is a great need to develop viable solid-state storage materials.
Magnesium: With a theoretical reversible hydrogen uptake value of 7.6 weight%, Mg is a candidate for a new storage medium. However, the hydrogen sorption temperature needs to be reduced (from around 300°C to 100-150°C), and the kinetics need to be accelerated. It has been shown that the sorption kinetics can be greatly improved by: introducing a nanoscale microstructure to provide a pathway for hydrogen diffusion; and by catalyzing the surface. The thermodynamics now need to be improved by alloying Mg to form a new compound or phase. Our work is investigating nanostructured Mg alloys produced by ball-milling, thin-film multilayers, and by rapid solidification.
Complex Hydrides: Borohydride compounds are promising hydrogen storage materials (e.g. lithium borohydride is able to store up to 18 wt%), but which require elevated temperatures (200 – 300°C) for hydrogen desorption and suffer poor reversibility (i.e. re-absorption of hydrogen is difficult). We are investigating Transition-metal-based borohydrides, produced by ball-milling and by high-pressure synthesis. We have found that the hydrogen desorption temperature in such compounds can be greatly reduced. We are now using in situ XRD and Raman spectroscopy (with 100 bar hydrogen cells) to study the phases that form during hydrogen desorption and reabsorption, with the aim of producing more reversible materials.
Nanocarbons: nanostructured graphite-based materials may store up to 7 wt% hydrogen, which offers the prospect of an inexpensive, widely available storage media. However, this material needs to be heated to 800°C to remove all the hydrogen, and reversibility is poor (limited to a few cycles after mixing with LiH). In order to improve the reabsorption process, we are studying how the hydrogen is stored, the role of carbon ‘dangling bonds’, and the effect of microstructure.
Hydrogen Separation Membranes
Any important challenge is how to provide extremely pure hydrogen, for use with PEM Fuel Cells?
Hydrogen produced from natural gas reformers and from biomass sources, usually contains small amount of impurity gases, such as carbon monoxide, methane, and sulphur. A PEM Fuel Cell converts hydrogen and oxygen gases into electricity; however, even very small amounts of impurities in the hydrogen can reduce the operating life of the Fuel Cell. In addition, there are applications in semiconductor and LED manufacture that require ultra-pure hydrogen.
Metallic diffusion membranes can be used to purify hydrogen: certain Pd-based alloys will allow only hydrogen gas to pass through (the impurity gas molecules are too large), resulting in parts-per-billion level pure hydrogen. However, the conventional membrane alloy used (Pd-Ag) is rather expensive, and cannot be used in the presence of impurities such as CO and S. We are investigating materials with less or no Pd with comparable membranes properties. We have also been studying the fabrication of thin-film composite membranes, which are deposited onto porous metallic substrates.
Permanent magnets are now essential components in many fields of technology, and have found applications in a wide range of devices. In 1984, the Nd2Fe14B magnet phase was developed by: powder metallurgy to form anisotropic, fully dense sintered magnets; and melt-spinning to produce isotropic magnetic powders, which can then be compacted to form bonded magnets. Although bonded magnets have poorer magnetic properties, the ability to form complex geometries has lead to bonded magnets becoming the fastest growing sector of the permanent magnet market.
Therefore, there was great interest in 1989, when a new technique – which came to be called Hydrogen Disproportionation Desorption Recombination (HDDR) – was developed, that subsequently allowed the production of anisotropic magnetic powders (anisotropic magnet powders have better magnetic properties than isotropic). The HDDR process involves exposing ingots of Nd-Fe-B to a series of carefully controlled heat treatments under hydrogen and vacuum. However, the mechanism behind the formation of anisotropic material is still not clear, and is now being investigated.
Zirconium alloys are used to clad nuclear fuel in light water reactors. The effect of hydrogen on the properties of zirconium alloys is one of the most significant factors that restricts the total amount of energy produced from a reactor. During service, when the solubility of hydrogen in zirconium is exceeded, various hydrides are formed that decrease the lifetime of the component by decreasing ductility and fracture toughness. Therefore, there is a need for a more detailed understanding of how such hydrides form to improve in-service component properties. We are working with UK partners to investigate the effect of microstructure on the diffusion of hydrogen and hydride formation in Zr alloys.
Y Zhang, D Book (2011) Hydrogen storage properties of ball-milled graphite with 0.5 wt% Fe. International Journal of Energy Research, Article in Press.
D Reed and D Book (2011) Recent applications of Raman spectroscopy to the study of complex hydrides for hydrogen storage. Current Opinion in Solid State and Materials Science 15 62-72 [doi:10.1016/j.cossms.2010.12.001 ]
S Tedds, A Walton and D Book (2011), Characterisation of Porous Hydrogen Storage Materials: Carbons, Zeolites, MOFs and PIMs. Faraday Discussions 151, Accepted for Publication
AI Bevan,A Züttel,D Book,and IR Harris (2011) Performance of a metal hydride store on the “Ross Barlow” hydrogen powered canal boat. Faraday Discussions 151, Accepted for Publication
D Ravnsbæk, C Frommen, Y Filinchuk, M Sørby, B Hauback, HJ Jacobsen, D Book, F Besenbacher, J Skibsted, TR Jensen (2011) Structural studies of lithium zinc borohydride by neutron powder diffraction, Raman and NMR spectroscopy. Journal of Alloys and Compounds, Article in Press, Corrected Proof [doi:10.1016/j.jallcom.2010.11.008]
D Reed and D Book (2011) Recent applications of Raman spectroscopy to the study of complex hydrides for hydrogen storage. Current Opinion in Solid State and Materials Science, Article in Press, Corrected Proof [doi:10.1016/j.cossms.2010.12.001 ]
B.S. Ghanem, M. Hassan, K.D.M. Harris, K.J. Msayib, M. Xu, P.M. Budd, N. Chaukura, D. Book, S. Tedds, A. Walton and N.B. McKeown (2010) Triptycene-based polymers of intrinsic microporosity: organic materials that can be tailored for gas adsorption. Macromolecules 43 5287-5294
DB Ravnsbæk, LH Sørensen, Y Filinchuk, D Reed, D Book, HJ Jakobsen, F Besenbacher, J Skibsted and TR Jensen (2010) Mixed-anion and Mixed-cation Borohydride KZn(BH4)Cl2: Synthesis, Structure and Thermal Decomposition. European Journal of Inorganic Chemistry 2010 1608-1612
Y Kim, D Reed, Y-S Lee, J-H Shim, HN Han, D Book, YW Cho (2010) Hydrogenation reaction of CaH2 - CaB6 - Mg mixture. Journal of Alloys and Compounds 492 597-600
B Paik, IP Jones, A Walton, V Mann, D Book, IR Harris (2010). Evolution of microstructure in MgH2 powder particles during high energy ball milling and hydrogen cycling. Journal of Alloys and Compounds 492 515-520
B Paik, IP Jones, A Walton, V Mann, D Book, IR Harris (2010) MgH2 → Mg phase transformation driven by a high-energy electron beam: An in situ transmission electron microscopy study. Philosophical Magazine Letters 90 1-7
J-H Shim, J-H Lim, S Rather, Y-S Lee, D Reed, Y Kim, D Book and YW Cho (2010) Effect of Hydrogen Back Pressure on Dehydrogenation Behavior of LiBH4-Based Reactive Hydride Composites. Journal of Physical Chemistry Letters 1 59-63
D Reed and D Book (2009) In situ Raman Studies of the Decomposition of Lithium Borohydride. Materials Research Society Symposium Proceedings 1216 1216-W06-05
KJ Msayib, D Book, PM Budd, N Chaukura, KDM Harris, M Helliwell, S Tedds, A Walton, JE Warren, M Xu, NB McKeown (2009) Nitrogen and Hydrogen Adsorption by an Organic Microporous Crystal Retrieved from the Cambridge Structural Database. Angewandte Chemie 48 3273-3277
Y Kim, D Reed, Y-S Lee, J Lee, J-H Shim, D Book, YW Cho (2009) Identification of the Dehydrogenated Product of Ca(BH4)2. Journal of Physical Chemistry C 113 5865-5871
Y Pivak, R Gremaud, K Gross, M Gonsalez-Silveira, A Walton, D. Book, H Schreuders, B Dam and R Griessen (2009) Effect of the film substrate on the thermodynamic properties of the PdHx studied by hydrogenography. Scripta Materialia 60 348-351
AJ Ramirez-Cuesta, PCH Mitchell, DK Ross, PA Georgiev, PA Anderson, HW Langmi, A Walton and D Book (2007) Dihydrogen in zeolite CaX—An inelastic neutron scattering study. Journal of Alloys and Compounds 446-447 393-396
PM Budd, A Butler, J Selbie, K Mahmood, NB McKeown, B Ghanem, K Msayib, D. Book, A. Walton (2007) The potential of organic polymer-based hydrogen storage materials. Physical Chemistry Chemical Physics 9 1802-1808
AJ Ramirez-Cuesta, PCH Mitchell, DK Ross, PA Georgiev, PA Anderson, HW Langmi, A Walton and D Book (2007) Dihydrogen in cation-substituted zeolite X—An inelastic neutron scattering study. Journal of Materials Chemistry 17 2533-2539
NB McKeown, PM Budd, D Book (2007) Microporous polymers as potential hydrogen storage materials. Macromolecular Rapid Communications 28 995-1002
BS Ghanem, KJ Msayib, NB McKeown, KDM Harris, Z Pan, PM Budd, A Butler, J Selbie, D Book, AWalton (2007) A triptycene-based polymer of intrinsic microposity that displays enhanced surface area and hydrogen adsorption. Chemical Communications 1 67-69
NB McKeown, B Ghamen, KJ Msayib, PM Budd, CE Tattershall, K Mahmood, S Tan, D Book, HW Langmi, A Walton (2006) Towards polymer-based hydrogen storage materials: engineering ultramicroporous cavities within polymers of intrinsic microporosity. Angewandte Chemie 45 1804-1807
HW Langmi, D Book, A Walton, SR Johnson, MM Al-Mamouri, JD Speight, PP Edwards, IR Harris and PA Anderson (2005) Hydrogen storage in ion-exchanged zeolites. Journal of Alloys and Compounds 404-406 637-642
SR Johnson, PA Anderson, PP Edwards, I Gameson, JW Prendergast, M Al-Mamouri, D Book, IR Harris, JD Speight and A Walton (2005) Chemical activation of MgH2; a new route to superior hydrogen storage materials. Chemical Communications 22 2823-2825
S Sugimoto, S. and D Book, D. (2005), “HDDR Process for the Production of High Performance Rare-Earth Magnets”. In: Y Liu, DJ Sellmyer, D Shindo, JG Zhu, and GC Hadjipanayis (eds.) Handbook of Advanced Magnetic Materials. Springer (ISBN: 1402079834