Producing Alkali Metal Hydrides from Hydroxides.

In this study, a novel method for producing different alkali metal hydrides (NaH, KH, RbH, and CsH) from their corresponding metal hydroxides (NaOH, KOH, RbOH, and CsOH) is presented. For the production of NaH from NaOH, a variety of metallic reducing agents (Mg, Al, Si, CaH2, Cr, Mn, and Sr) were investigated. The reactions took place in an autoclave reactor with paraffin oil at 250 °C and 14 bar of H2 pressure. Splitting the process into two steps (metal formation and hydrogenation) simplified the separation and purification for the produced metal hydride. Moreover, the study explores the potential for this method of NaH production to be used for NaBH4 production and regeneration for hydrogen export applications. This approach offers an alternative, cost-effective method for producing NaH.

Divalent closo-monocarborane solvates for solid-state ionic conductors.

Li-ion batteries have held the dominant position in battery research for the last 30+ years. However, due to inadequate resources and the cost of necessary elements (e.g., lithium ore) in addition to safety issues concerning the components and construction, it has become more important to look at alternative technologies. Multivalent metal batteries with solid-state electrolytes are a potential option for future battery applications. The synthesis and characterisation of divalent hydrated closo-monocarborane salts - Mg[CB11H12]2·xH2O, Ca[CB11H12]2·xH2O, and Zn[CB11H12]2·xH2O - have shown potential as solid-state electrolytes. The coordination of a solvent (e.g. H2O) to the cation in these complexes shows a significant improvement in ionic conductivity, i.e. for Zn[CB11H12]2·xH2O dried at 100 °C (10-3 S cm-1 at 170 °C) and dried at 150 °C (10-5 S cm-1 at 170 °C). Solvent choice also proved important with the ionic conductivity of Mg[CB11H12]2·3en (en = ethylenediamine) being higher than that of Mg[CB11H12]2·3.1H2O (2.6 × 10-5 S cm-1 and 1.7 × 10-8 S cm-1 at 100 °C, respectively), however, the oxidative stability was lower (<1 V (Mg2+/Mg) and 1.9 V (Mg2+/Mg), respectively). Thermal characterisation of the divalent closo-monocarborane salts showed melting and desolvation, prior to high temperature decomposition.

Alkali metal alkoxyborate ester salts; a contemporary look at old compounds.

Research into the use of sodium tetraalkoxyborate salts for different chemical applications including synthetic catalysis, hydrogen storage, or battery applications has been investigated, however, understanding of the structural, thermal and electrochemical properties of these salts has been lacking since the 1950s and 1960s. A review of the synthesis, as well as a thorough characterization using 1H NMR, 11B NMR, 13C{1H} NMR, FTIR, XRD, in situ XRD, DSC-TGA, RGA-MS, TPPA, and EIS has newly identified polymorphic phase changes for Na[B(OMe)4], K[B(OMe)4], Li[B(OMe)4], Na[B(OEt)4], Na[B(OBu)4], and Na[B(OiBu)4]. The crystal structure of K[B(OMe)4] was also solved in I41/a (a = 22.337(2) Å, c = 7.648(3) Å, V = 3815.6(4) Å3, ρ = 1.128(1) g cm-3). Ionic conductivity of the different salts was analyzed, however it was found that the compounds with longer alkyl chains had no measurable ionic conductivity compared to the shorter chained samples, Na[B(OMe)4] and K[B(OMe)4] with 9.6 × 10-8 S cm-1 and 1.6 × 10-7 S cm-1, at 114 °C respectively.