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[摘要]：Manganese(II) hydrazide gels designed for Kubas-type hydrogen storage were synthesized from the reaction between bis(trimethylsilylmethyl) manganese and anhydrous hydrazine. The synthetic materials were characterized by X-ray powder diffraction, nitrogen adsorption, X-ray photoelectron spectroscopy, infrared spectroscopy, and elemental analysis. Hydrogen storage measurements were conducted on materials with hydrazine:Mn ratios of 0.5:1, 1:1. 1.5:1, and 2:1. The best results were obtained with the 1:1 material, which demonstrated as high as 1.01 wt % and 32 kg/m(3) at 77 K and 85 bar and 1.06 wt % and 24.2 kg/m(3) at 298 K at 85 bar. Measurements up to 143 bar at 298 K led to an adsorption value of 1.65 wt % and 37.7 kg/m(3) without saturation. The isosteric enthalpy of this material rose with surface coverage from 1.3 to 39 kJ/mol. Excess void space was removed from the materials by compressing at 500 Psi and the resulting compressed gel pellets possess an absolute volumetric adsorption of 18.97 kg/m(3) at 298 K and 85 bar. The mechanism of hydrogen storage was probed with electron paramagnetic resonance (EPR), which showed signal enhancements when sample was held under 1 bar hydrogen, both at room temperature and at 77 K. This was interpreted as a perturbation due to hydrogen binding to the Mn center. |
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