PROCESSING AND HYDROGEN DESORPTION PROPERTIES OF NOVEL LITHIUM BOROHYDRIDE (LIBH4)-BASED HYDROGEN STORAGE MATERIALS Kouassi Gaelle ANGUIE A thesis submitted for the degree of Master of Philosophy In the Graduate School of Science and Engineering School of Engineering and Materials Queen Mary, University of London 2016 To my late Father: Anguie Jean-Marcel Elie ANGUIE PREFACE Name of candidate: Kouassi Gaelle ANGUIE Degree for which entered: MPhil (MPhil / PhD / MD(Res)) Date of thesis submission: June 2016 Title of thesis: Processing and hydrogen desorption properties of novel lithium borohydride (LiBH4)-based hydrogen storage materials Name of principal supervisor: Pr. Z. Xiao GUO (UCL) Pr. Mike Reece (QMUL) Approximate word length of < 100,000 thesis: 1. Please tick one box: □ I confirm that the above thesis does not exceed the word limit prescribed in the Regulations. □ I confirm that the above thesis exceeds the word limit and has received a suspension of Regulations with attached confirmation. 2. I confirm that the work presented in the thesis is my own and all references are cited accordingly (if the thesis includes any work conducted jointly please attach a statement of the part played by the candidate, certified by the supervisor). I accept that the College has the right to use plagiarism detection software to check the electronic version of the thesis. Candidate signature: G. AKG Date: 23/06/2016 ACKNOWLEDGEMENT I would like to thank, Pr. Z. Xiao GUO, my academic supervisor who gave me the precious opportunity to study in two of UK’s best universities: QMUL and UCL. Knowing his multiple responsibilities, I am really grateful to his patient guidance and strong support throughout the four (4) years. Many thanks to Dr Kondo-Francois AGUEY-ZINSOU for his daily technical advice and support, his strong knowledge and experience benefit me and will continue during my research and development career after graduation. I would also like to express my sincere gratitude to my sponsors: UK-SHEC and EPSRC, to the School of Engineering and Materials Science at Queen Mary University of London and the Department of Chemistry at University College London where I had very helpful support from either academic or non-academic staff. Some names include: Pr. Mike Reece, John Caufield, Jonathon Hills, Martin Vickers, Victoria Wells, Andrew Humphrey… and many other people such as my colleagues (Shahrouz Nayebossadri, Elnaz Ajami, Negar Amini or Yiwen Wang) that were very supportive towards me. Then, I would like to greet my family, especially, my parents for their unconditional support and certainly at last but not least my beloved children Yohann-Ebony and Ayana for giving me the strength to continue and persevere despite the countless difficulties. I dedicate this thesis to my late dad, Mr. Anguie ANGUIE who passed away 5 years ago and never saw the end of it. I hope he is proud of my achievement from where he is. 1 ABSTRACT The primary aim of this project was the development of an inorganic Lithium borohydride (LiBH4)-based material for effective use in hydrogen storage. The objective was to find a material which would desorb a minimum of 5 wt.% H2 under mild conditions. To do so, LiBH4 has been investigated and the possibility to destabilise it so that it could release a maximum of its hydrogen content without losing boron, which is a requirement for reversible hydrogen storage. Why LiBH4? Lithium borohydride has one of the greatest hydrogen content (18.5 wt.%) among hydride materials. Nevertheless, the compound is very stable, hence the desorption temperature is too high for practical considerations. Hopefully, some interesting results have been reported by previous studies and opened the way for possible improvement mainly in terms of lowering the desorption temperature. The impact of chemical additions such as transition metal chlorides and ammonium chloride (NH4Cl) to its thermostability has been assessed. NH4Cl has a number of advantages compared to transition metal chlorides since it contains hydrogen, is less heavy and is a precursor to ammonia borane (NH3BH3), another promising material for solid-state hydrogen storage applications. Mass spectrometry and thermal analysis of mixtures of LiBH4 and NH4Cl indicate that contrary to the results obtained with the addition of transition metal chlorides where a significant amount of B2H6 escapes from the mixture upon heating, sole release of hydrogen may be obtained. Moreover, the onset hydrogen desorption may be as low as 65ºC for (LiBH4 + NH4Cl) mixtures, similarly to the one observed for (2LiBH4 + ZnCl2) mixtures. In the case of NH4Cl-added mixtures, the proportion of H2 released is much higher, around 2 wt.% at this temperature. Also, sole release of up to 6 wt. % hydrogen may be achieved at temperatures as low as 150ºC, which is a huge improvement compared to pure LiBH4, transition metal chlorides added mixtures and even NH3BH3. This whole study shows the clear potential for using B-N-H compounds as high- capacity hydrogen storage applications. 2 List of contents – Chapters and sub-chapters LIST OF CHAPTERS AND SUB-CHAPTERS COVER.................................................................................................................................0 PREFACE.............................................................................................................................0 ACKNOWLEDGEMENT S.................................................................................................1 ABSTRACT..........................................................................................................................2 LIST OF CONTENTS..........................................................................................................3 LIST OF CHAPTERS AND SUB-CHAPTERS......................................................3 LIST OF FIGURE CAPTIONS................................................................................8 LIST OF TABLES..................................................................................................19 LIST OF EQUATIONS..........................................................................................22 CHAPTER 1 General introduction ..........................................................................29 CHAPTER 2 Overview of hydrogen storage.......................... ....................................39 2.1 Hydrogen storage issues and methods................................................................40 2.1.1 Hydrogen Storage Challenges for on-board applications...........................40 2.1.2 Hydrogen storage methods.........................................................................42 2.1.2.1 Gaseous hydrogen...................................................................................42 2.1.2.2 Liquid hydrogen......................................................................................46 2.1.2.3 Hydrogen in solids..................................................................................49 2.2 Research on complex hydrides............................................................................65 2.2.1 Alanates.......................................................................................................65 3 List of contents – Chapters and sub-chapters 2.2.1.1 Sodium alanate, NaAlH4.........................................................................66 2.2.1.2 Lithium alanate, LiAlH4..........................................................................66 2.2.1.3 Other alanates: Mg(AlH4)2 and KAlH4...................................................67 2.2.2 Amides-based complex systems..................................................................68 2.2.2.1 Lithium amide, LiNH2.............................................................................68 2.2.2.2 Association with metal hydrides.............................................................69 2.2.2.3 Association with complex hydrides: alanates and borohydrides............71 2.2.3 Borohydrides...............................................................................................72 2.2.3.1 Background information.........................................................................72 2.2.3.2 Preparation and synthesis........................................................................75 2.2.3.3 Properties and applications of borohydride compounds.........................87 2.2.3.4 Borohydrides for hydrogen storage applications....................................89 2.2.4 Amine-borane systems................................................................................98 2.2.4.1 Ammonia borane (AB)...........................................................................98 2.2.4.2 Diammoniate of diborane (DADB).......................................................102 2.2.4.3 Borazole (also known as borazine, BZ)................................................103 2.2.4.4 Other volatile B-N-H compounds.........................................................105 CHAPTER 3 Experimental methods...........................................................................107 3.1 Sample preparation............................................................................................108 3.1.1 Materials....................................................................................................108 3.1.2 Pre-treatment of powder mixtures.............................................................109 3.1.3 Mechanical milling....................................................................................110