Multivalent ManganeseHydrazide Gels for Kubas-TypeHydrogen Storage.

Manganese(II) hydrazide gels designed for Kubas-typehydrogen storagewere synthesized from the reaction between bis(trimethylsilylmethyl)manganese and anhydrous hydrazine. The synthetic materials were characterizedby X-ray powder diffraction, nitrogen adsorption, X-ray photoelectronspectroscopy, infrared spectroscopy, and elemental analysis. Hydrogenstorage measurements were conducted on materials with hydrazine:Mnratios of 0.5:1, 1:1. 1.5:1, and 2:1. The best results were obtainedwith the 1:1 material, which demonstrated as high as 1.01 wt % and32 kg/m3at 77 K and 85 bar and 1.06 wt % and 24.2 kg/m3at 298 K at 85 bar. Measurements up to 143 bar at 298 K ledto an adsorption value of 1.65 wt % and 37.7 kg/m3withoutsaturation. The isosteric enthalpy of this material rose with surfacecoverage from 1.3 to 39 kJ/mol. Excess void space was removed fromthe materials by compressing at 500 Psi and the resulting compressedgel pellets possess an absolute volumetric adsorption of 18.97 kg/m3at 298 K and 85 bar. The mechanism of hydrogen storage wasprobed with electron paramagnetic resonance (EPR), which showed signalenhancements when sample was held under 1 bar hydrogen, both at roomtemperature and at 77 K. This was interpreted as a perturbation dueto hydrogen binding to the Mn center. [ABSTRACT FROM AUTHOR]