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Experimental and theoretical studies of boron and hydrogen containing compounds in relation to potential hydrogen storage and ionic conduction applications

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Defense Thèse de doctorat : Univ. Genève, 2017 - Sc. 5101 - 2017/06/23
Abstract This thesis deals with the fundamental studies of some materials containing boron-hydrogen bonds which can potentially be used either as the hydrogen storage materials (M(BH4)2, M=Alkaline earth metal), as the solid electrolytes for batteries (Na2B12H12) or as reducing agents for CO2 (Mg(BH4)2). First part of thesis deals with borohydrides (BH4-). Synthesis and characterization of halide-free Sr(BH4)2, Ba(BH4)2 and Eu(BH4)2 is reported. Crystallographic study of these compounds helped in identifying several new phases and a new species metal borohydride hydride (M2(BH4)H3). In depth study of B-H bond breaking is reported via isotope exchange reaction in Ca(BH4)2.A practical example of borohydride as reducing agent is reported by showing the reduction of CO2 with gamma-Mg(BH4)2. The second part of the thesis focuses on closoboranes derived from the B12H122- ion. Compounds of this family have recently attracted great interest as solid ionic conductors for Li and Na ions.Results of DFT calculations on isolated B12H122- anions and halogen (F, Cl or Br) substituted anions were analysed in detail. Synthesis of Na2B12(SCN)H11 is reported.The measurement of the ionic conductivity of this sample shows that the conductivity at room temperature is much better (1000 fold) compared to pristine Na2B12H12.
Keywords BorohydridesClosoboranesNa2B12H12Sr(BH4)2Eu(BH4)2Ba(BH4)2Thiocyanated closoboraneNa2B12H11(SCN)Mg(BH4)2Isotope ExchangeCa(BH4)2FTIRMetal borohydride hydrideM2(BH4)2H3Halide free metal borohydrideReduction of CO2B12H12-nXn 2-Vibrational spectroscopySubstituted closoborane,
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URN: urn:nbn:ch:unige-963769
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SHARMA, Manish. Experimental and theoretical studies of boron and hydrogen containing compounds in relation to potential hydrogen storage and ionic conduction applications. Université de Genève. Thèse, 2017. https://archive-ouverte.unige.ch/unige:96376

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Deposited on : 2017-08-30

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