TY - JOUR

T1 - Synthesis, crystal structure and thermal stability of tetrahydroborate sodalite Na8[AlSiO4]6(BH4) 2

AU - Buhl, J. Ch

AU - Gesing, Th M.

AU - Rüscher, C. H.

N1 - Funding Information: The authors are greatly indebted to M.M. Murshed (University of Hannover) for carrying out the MAS NMR spectra. This work was supported by the DFG.

PY - 2005/5/2

Y1 - 2005/5/2

N2 - Tetrahydroborate sodalite formation was investigated in the system Na 2O-SiO2-Al2O3-NaBH 4-H2O under mild hydrothermal conditions. Due to the high degree of decomposition of hydroborates in aqueous solutions synthesis conditions were tuned by variation of the parameters alkalinity, liquid/solid ratio, reaction temperature and reaction time. The insertion of 8-16 molar NaOH solution was crucial for the higher stability of pure tetrahydroborate salt under strong alkaline conditions. Synthesis at 393 K and 24 h reaction time reveal tetrahydroborate sodalite Na8[AlSiO4] 6(BH4)2 beside a small amount of amorphous material within the total batch. Structure, composition and thermal stability of this new sodalite was investigated using XRD, NMR, infrared and TG/DTA methods. The crystal structure of tetrahydroborate sodalite has been refined in the space group P-43n with a = 891.61(2) pm. The Si- and Al-atoms of the aluminosilicate framework are completely ordered. The boron atoms of the tetrahydroborate anions are located at the centre of the sodalite cage whereas the hydrogen atoms are positionally disordered. Na8[AlSiO 4]6(BH4)2 shows a high stability under inert gas conditions. At atmospheric conditions the BH4- group can be oxidized to borate and boroxide anions suggesting the formation of hydrogen which leaves the sodalite cages. Future investigation of reloading properties of the oxidized form could be highly interesting for the hydrogen storage capabilities of these sodalites.

AB - Tetrahydroborate sodalite formation was investigated in the system Na 2O-SiO2-Al2O3-NaBH 4-H2O under mild hydrothermal conditions. Due to the high degree of decomposition of hydroborates in aqueous solutions synthesis conditions were tuned by variation of the parameters alkalinity, liquid/solid ratio, reaction temperature and reaction time. The insertion of 8-16 molar NaOH solution was crucial for the higher stability of pure tetrahydroborate salt under strong alkaline conditions. Synthesis at 393 K and 24 h reaction time reveal tetrahydroborate sodalite Na8[AlSiO4] 6(BH4)2 beside a small amount of amorphous material within the total batch. Structure, composition and thermal stability of this new sodalite was investigated using XRD, NMR, infrared and TG/DTA methods. The crystal structure of tetrahydroborate sodalite has been refined in the space group P-43n with a = 891.61(2) pm. The Si- and Al-atoms of the aluminosilicate framework are completely ordered. The boron atoms of the tetrahydroborate anions are located at the centre of the sodalite cage whereas the hydrogen atoms are positionally disordered. Na8[AlSiO 4]6(BH4)2 shows a high stability under inert gas conditions. At atmospheric conditions the BH4- group can be oxidized to borate and boroxide anions suggesting the formation of hydrogen which leaves the sodalite cages. Future investigation of reloading properties of the oxidized form could be highly interesting for the hydrogen storage capabilities of these sodalites.

KW - Crystal structure

KW - Hydrogen storage

KW - Synthesis

KW - Tetrahydroborate sodalite

KW - Thermal behaviour

UR - http://www.scopus.com/inward/record.url?scp=16644381781&partnerID=8YFLogxK

U2 - 10.1016/j.micromeso.2004.11.022

DO - 10.1016/j.micromeso.2004.11.022

M3 - Article

AN - SCOPUS:16644381781

VL - 80

SP - 57

EP - 63

JO - Microporous and Mesoporous Materials

JF - Microporous and Mesoporous Materials

SN - 1387-1811

IS - 1-3

ER -