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Synthesis and structure determination of complex zinc hydrides Part 3. Dirubidium- and dicaesiumtetrahydridozincate(II), Rb2ZnH4 and Cs2ZnH4

1997; Elsevier BV; Volume: 248; Issue: 1-2 Linguagem: Inglês

10.1016/s0925-8388(96)02580-7

1873-4669

M. Bortz, A.W. Hewat, K. Yvon,

Hydrogen Storage and Materials

Abstract Rb 2 ZnH 4 , Cs 2 ZnH 4 and the corresponding deuterides were prepared by sintering stoichiometric amounts of the binary alkali hydrides (deuterides) and zinc powder under hydrogen (deuterium) pressure of 80 bar at 650 K. X-ray and neutron powder diffraction on the deuterides show that the compounds are isotypic with K 2 ZnH 4 and crystallize in the β-K 2 SO 4 structure type, space group Pnma (No. 62), Z = 4. Zinc is tetrahedrally coordinated by deuterium with average ZnD bond distances of 1.673 A (Rb) and 1.682 A (Cs). The decomposition temperature at 1 bar hydrogen pressure is 640(15)K for the Rb and 645(15)K for the Cs compound. The hydrogen storage efficiencies are 1.7 wt.% (50.7 g H 2 l −1 ) for Rb 2 ZnH 4 and 1.2 wt.% (44.4 g H 2 I −1 ) for Cs 2 ZnH 4 .