Design and Synthesis of New Hydrogen Storage Materials Functioning by Weak Chemisorption
Abstract
In the first project, hexagonal packed mesoporous silica (HMS) was synthesized, using dodecyl amine as neutral templating agent. Bis(benzene) and bis(cylopentadienyl) V and Cr were treated with HMS arriving in doping level of 5 wt % for Kubas-type hydrogen adsorption. All doped materials had higher hydrogen adsorption capacities than that of pristine silica. Each Cr center could accommodate 2.2 H2 molecules at 77 K and 60 bar while each V center adsorbs 1.73 H2 at the same condition. The Cr doped silica preserved a substantial degree of its adsorption at room temperature and after three months storage in an inert atmosphere. The second project involved in the synthesis and hydrogen storage performance of vanadium hydrazide gels. The third project focused on the manganese hydrazide for hydrogen storage. The fourth project concentrated on the preparation of titanium hydrazide gels for hydrogen storage. These materials used low-coordinate metal centers as the principal Kubas H2 binding sites with only negligible contribution of physisorption. Hydrazide samples were characterized by Powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), Infrared Spectroscopy (IR), Elemental Analysis (EA), Electron Paramagnetic Resonance (EPR), Raman Spectroscopy, nitrogen adsorption (BET), and hydrogen adsorption. The vanadium hydrazide gels possess an excess reversible storage of 4.04 wt% at 77 K and 85 bar, corresponding to a true volumetric adsorption of 80 kg/m3 and an excess volumetric adsorption of 60.01 kg/m3. These values are in the range of the ultimate DOE goal for volumetric density (70 kg/m3) while the manganese hydrazide gels possess 24.2 kg/m3 volumetric at 298K and 85bar. The fifth project employed commercially available organic compounds to react with V(Mes)3.THF to create vanadium-containing polymers for hydrogen storage. The sixth project involved in the synthesis of a porous titanium(III) hydride for hydrogen storage. Ti(III) hydride gels are a promising new hydrogen storage medium, which exploit the first example of solid-state hypervalent hydrides. The material with the highest capacity has an excess reversible storage of 3.49 wt % at 140 bar and 298 K, which corresponds to 44.3 kg/m3 of volumetric density, surpassing the DOE 2017 volumetric goal of 40 kg/m3 H2 without saturation. At adsorption level of 3.49 wt%, TiH3 is be converted to hypervalent TiH5 and TiH7, which contain 3.93 wt% and 7.86 wt% H2, respectively. There are high expectations that hydrogen storage performance of hydrazide and hydride materials might provide even higher storage capacities at higher hydrogen pressure in this thesis so that a system contains these materials might surpass the US Department of Energy ultimate system targets (7.5 wt% and 70 kg/m3