Design and Synthesis of Vanadium Hydrazide Gels for Kubas-Type Hydrogen Adsorption: A New Class of Hydrogen Storage Materials

Abstract

In this paper we demonstrate that the Kubas interaction, a nondissociative form of weak hydrogen chemisorption with binding enthalpies in the ideal 20-30 kJ/mol range for room-temperature hydrogen storage, can be exploited in the design of a new class of hydrogen storage materials which avoid the shortcomings of hydrides and physisorpion materials. This was accomplished through the synthesis of novel vanadium hydrazide gels that use low-coordinate V centers as the principal Kubas H(2) binding sites with only a negligible contribution from physisorption. Materials were synthesized at vanadium-to-hydrazine ratios of 4:3, 1:1, 1:1.5, and 1:2 and characterized by X-ray powder diffraction, X-ray photoelectron spectroscopy, nitrogen adsorption, elemental analysis, infrared spectroscopy, and electron paramagnetic resonance spectroscopy. The material with the highest capacity possesses an excess reversible storage of 4.04 wt % at 77 K and 85 bar, corresponding to a true volumetric adsorption of 80 kg H(2)/m(3) and an excess volumetric adsorption of 60.01 kg/m(3). These values are in the range of the ultimate U.S. Department of Energy goal for volumetric density (70 kg/m(3)) as well as the best physisorption material studied to date (49 kg H(2)/m(3) for MOF-177). This material also displays a surprisingly high volumetric density of 23.2 kg H(2)/m(3) at room temperature and 85 bar--roughly 3 times higher than that of compressed gas and approaching the DOE 2010 goal of 28 kg H(2)/m(3). These materials possess linear isotherms and enthalpies that rise on coverage and have little or no kinetic barrier to adsorption or desorption. In a practical system these materials would use pressure instead of temperature as a toggle and can thus be used in compressed gas tanks, currently employed in many hydrogen test vehicles, to dramatically increase the amount of hydrogen stored and therefore the range of any vehicle.

Room Temperature Hydrogen Physisorption on Exposed Metals in A Highly Cross‐Linked Organo‐Iron Complex

“…In comparison with the class-two compounds, the MTF-Fe complex exhibits a porous network with a substantially lower loading of metals by up to 5 fold and higher thermal stability up to 420 °C. The excess hydrogen capacity of the MTF-Fe complex at 298K is comparable to the previously reported values of class-two materials, such as H 2 -Cr-MHz (1.0) (1.65 wt% at 85 atm), [ 8 ] vanadium hydride gel C150 (1.17 wt% at 85 atm), [ 20 ] and manganese hydride gel B100 (1.06 wt% at 85 atm). [ 7 ] To further understand the strong H 2 -host interaction, we performed fi rst principles calculations using density functional theory on the local structure in the proximity of Fe atom before and after 1.4 wt% H 2 uptake.…”

Pore-expanded MCM-41 for CO2 adsorption: Experimental and isotherm modeling studies

“…The value of DH iso at zero loading is found to be $21 kJ/mol and is comparable to the reported typical values (20 kJ/mol) for MCM-41 silica [47]. The obtained amount of heat of adsorption is much smaller than 40 kJ/mol, typical heat of adsorption for chemisorptions [56,57]. This indicates that the process of CO 2 adsorption on PE-MCM-41 is governed by physisorption.…”

Synthesis of Zn-MOF incorporating titanium-hydrides as active sites binding H2 molecules

“…A variety of materials site-isolating these active transition metals have been computationally demonstrated to bind H 2 molecules via Kubas-type interaction [19,20]. In contrast, to the best of our knowledge, there have been few reports detailing the synthesis of these materials experimentally except the studies conducted by D. M. Antonelli and co-workers [24][25][26][27]. The transition metal sites inherent to these materials, however, were tri-and/or tetra-coordinated to bulk ligands [24][25][26][27], thereby potentially reducing the number of H 2 molecules theoretically bound to these sites [19,20,22,23].…”

“…In contrast, to the best of our knowledge, there have been few reports detailing the synthesis of these materials experimentally except the studies conducted by D. M. Antonelli and co-workers [24][25][26][27]. The transition metal sites inherent to these materials, however, were tri-and/or tetra-coordinated to bulk ligands [24][25][26][27], thereby potentially reducing the number of H 2 molecules theoretically bound to these sites [19,20,22,23]. In addition, the presence of oxygen atoms inherent to the support (e.g., SiO 2 [26] and TiO 2 [27]), some of which are vicinal to the transition metal active sites, can potentially lead to the coordination of these oxygen atoms to these sites [26,28].…”