Bulletin of the American Physical Society
2008 APS March Meeting
Volume 53, Number 2
Monday–Friday, March 10–14, 2008; New Orleans, Louisiana
Session S36: Focus Session: Hydrogen Storage III: Novel Porous and Sorbent Materials |
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Sponsoring Units: DMP FIAP Chair: Hui Wu, NIST Center for Neutron Research Room: Morial Convention Center 228 |
Wednesday, March 12, 2008 2:30PM - 3:06PM |
S36.00001: Enhancing the interaction strength and capacities of hydrogen storage via surface adsorption Invited Speaker: Storing Hydrogen molecules in porous media based on a physisorption mechanism is one possible approach to reach the US Department of Energy targets for on-board hydrogen storage. Although the storage capacities of metal-organic frameworks (MOFs) have progressed significantly over recent years, some technological obstacles pose challenges for their future improvement. These include the generally low H$_{2}$ adsorption enthalpy limiting room temperature applications and the lack of understanding of surface packing density hindering the efficient improvement of H$_{2}$ adsorption uptake. To improve the H$_{2}$ affinity in MOFs, our previous work has shown that the coordinatively unsaturated metal centers (CUMCs) can greatly enhance the H$_{2}$ binding strength. Our current study of MOF-74 will be presented, showing that its open Zn$^{2+}$ ions bind H$_{2}$ strongly and are identified as being responsible for the large initial H$_{2}$ adsorption enthalpy of 8.4 kJ/mol. In all, there are four H$_{2}$ adsorption sites in MOF-74 identified by neutron powder diffraction. These four hydrogen adsorption sites are closely packed in MOF-74 and form a one dimensional nanoscale tube structure. We also demonstrate an interesting correlation that MOFs with CUMCs generally show larger surface packing densities than that of other MOFs without CUMCs. The implications of this will be addressed. [Preview Abstract] |
Wednesday, March 12, 2008 3:06PM - 3:18PM |
S36.00002: Nature of the Hydrogen Binding in Metal Organic Frameworks with Exposed Transition Metal Sites Wei Zhou, Taner Yildirim MOFs with exposed transition metal (TM) sites were recently found to exhibit significantly larger experimental heat of H$_{2}$ adsorption than classical MOFs, thus attracted great attention. [1, 2] Understanding the nature of the H$_{2}$ interaction with the exposed metal sites is of critical importance for the further development of these materials. Using Mn$_{4}$Cl-MOF as an example, here we show that the H$_{2}$ binding with the exposed TM site is not of the expected Kubas type, in strong contrast to ``similar'' systems investigated previously (e.g., ref. [3] and [4]). In Mn$_{4}$Cl-MOF, there are a) no charge transfer from TM to H$_{2}$, b) no significant H-H bond elongation, and c) no evidence of any H$_{2}$-\textit{$\sigma $}$^{\ast }$ Mn-$d$ orbital hybridization. We also study the H$_{2}$ binding as a function of Mn$_{4}$-magnetic spin configurations, and find no significant effect of the magnetic state on the binding energy. We further reveal that the major contribution to the overall binding is classical Coulomb interaction arising from the small charge overlap of H$_{2}$-\textit{$\sigma $} and Mn-$d$ orbitals. This coulomb interaction is very anisotropic, and when the quantum nature of H$_{2}$-orientation is taken into account, the actual binding energy is significantly reduced from the calculated classical binding energy. [1] J. Am. Chem. Soc. 128, 16876 (2006). [2] Angew. Chem. Int. Ed. 46, 1419 (2007). [3] Phys. Rev. Lett. 94, 087205 (2005). [4] Phys. Rev. B 76, 085434 (2007). [Preview Abstract] |
Wednesday, March 12, 2008 3:18PM - 3:30PM |
S36.00003: Kinetic and steric differences in adsorption in two porous metal-organic frameworks Kathleen Lask, Vaiva Krungleviciute, Murat Bulut, Aldo Migone, J.-Y. Lee, Jing Li Kinetic and steric differences are two of the three fundamental mechanisms underlying the use of adsorption in applications to gas mixture separations. We present experimental results on kinetics and equilibrium adsorption measurements of tetrafluoromethane and argon on two metal-organic framework (MOF) materials: RPM1-Co or [Co$_{3}$(bpdc)$_{3}$bpy]$\cdot $4DMF$\cdot $H$_{2}$O] (bpdc = biphenyldicarboxylate, bpy = 4,4$\prime $-bipyridine, DMF = N,N- dimethylformamide) and Cu-BTC or Cu$_{3}$(BTC)$_{2}$(H$_{2}$O)$_{3}$ (BTC = benzene-1,3,5-tricarboxylate). The adsorbates display significant differences in their kinetics on RPM1-Co (i.e., there are sizable differences in the time required for each gas to reach equilibrium after it is allowed access to the substrate). Our equilibrium measurements show that CF$_{4}$ is sterically precluded from adsorbing in the small tetrahedral-shaped side pockets present in Cu-BTC. We will compare our experimental results with predictions for how adsorption kinetics depends on the size of the adsorbate and on those of the pores present in the substrate. [Preview Abstract] |
Wednesday, March 12, 2008 3:30PM - 3:42PM |
S36.00004: A theoretical and experimental study of hydrogen storage in metal organic framework materials. Valentino R. Cooper, Jeong Yong Lee, Jing Li, Yves Chabal, David C. Langreth Metal-organic framework (MOF) materials, assembled by linking metal ions or clusters through molecular bridges, have been shown to be good candidates for H$_2$ storage. We have been successful in fabricating and characterizing MOFs with increased H$_2$ uptake\footnote{J. Y. Lee et al. Adv. Func. Mater., \textbf{17}, 1255 (2007)}, though still too low for commercial applications. Here we present a coordinated theoretical-experimental effort to understand the mechanism of H$_2$ adsorption in true MOF materials. Using the completely \emph{ab initio} van der Waals density functional (vdW-DF)\footnote{M. Dion et al. Phys. Rev. Lett., \textbf{92}, 246401 (2004)}$^,$\footnote{T. Thonhauser et al. Phys. Rev. B, \textbf{76}, 125112 (2007)} we simulate the interactions of H$_2$ within Zn$_2$(bdc)$_2$(ted). We demonstrate that modeling the entire MOF structure can result in different H$_2$ adsorption geometries, binding energies and vibrational frequencies than observed in calculations on fragments of the MOF. Combining these results with experimental IR vibrational frequency studies may provide insights into modifying MOF structure and composition for enhanced H$_2$ uptake. [Preview Abstract] |
Wednesday, March 12, 2008 3:42PM - 3:54PM |
S36.00005: The flexibility of zeolites for Hydrogen storage Asel Sartbaeva, Stephen Anthony Wells, Peter P. Edwards The flexibility window is a newly discovered theoretical measure which can provide a valuable selection criterion when evaluating hypothetical zeolite framework structures as potential synthetic targets. Today synthetic zeolites are the most important catalysts in petrochemical refineries. There have been considerable efforts to synthesize new zeolites with specific pore geometries, to add to the 167 available at present. Millions of hypothetical structures have been generated on the basis of energy minimization, and there is an ongoing search for criteria capable of predicting new zeolite structures. The flexibility window appears to be a property of existing zeolite frameworks not shared by many hypothetical structures. It provides a valuable selection criterion when evaluating hypothetical zeolite framework structures as potential synthetic targets. We are investigating the use of zeolites as hydrogen storage materials, as small molecules such as molecular hydrogen and ammonia can be easily absorbed into a flexible framework of zeolites. An exiting possibility is the use of framework flexibility to control hydrogen uptake, storage and release. This would allow a safe use of hydrogen for fuel cells. [Preview Abstract] |
Wednesday, March 12, 2008 3:54PM - 4:06PM |
S36.00006: Inelastic Incoherent Neutron Scattering Studies of the Ti-doped hydrogen-adsorbed SBA-15 Alice I. Acatrinei, Luke L. Daemen, Monika A. Hartl The discovery in 1998 of the hydrothermally stable SBA-15 by Zhao et al. [1] represents a great advance in the synthesis of ordered mesoporous materials. The high porosity, good thermal stability, and low specific weight of these materials makes them good candidates for hydrogen storage research, and metal doping shows an enhancement of their properties and gas storage capabilities. We used inelastic incoherent neutron scattering to look at both Ti-doped and undoped hydrogen adsorbed SBA-15. Powder XRD measurements confirmed the mesoporosity of the material. Adsorbtion isotherm showed that a significant amount of hydrogen was adsorbed in the compound. Our results indicate that hydrogen bonds to the Ti centers in the material. [1]. D. Zhao, J. Feng, Q. Huo, N. Melosh, G.H. Fredrickson, B.F. Chmelka, G.D. Stucky, Science 279 (1998) 548. [Preview Abstract] |
Wednesday, March 12, 2008 4:06PM - 4:18PM |
S36.00007: Hydrogen Storage in Mesoporous Materials under High Pressure Michelle Weinberger, Maddury Somayazulu, Russell Hemley To date, the materials considered best candidates for hydrogen storage fuel cells include activated carbon and metal organic frameworks. Both very high surface area activated carbon and MOF-5 have been shown to adsorb around 4.5 wt {\%} of hydrogen gas at 78 K. We have investigated the fundamental structural response of these materials to high pressure, as well as their behavior at high pressure when packed with dense hydrogen. Further investigation of these materials at low temperatures while still at elevated pressures may in fact provide a route for recovery of these hydrogen-packed materials to near ambient conditions. Covalent organic frameworks offer the potential for even better hydrogen storage capacity. These materials have significantly lower densities than the MOF materials and offer a significantly larger number of adsorption sites. Diamond anvil cells are uniquely suited for the study of these materials, allowing in situ measurements at high pressure as well as at low temperatures. Using X-ray diffraction and Raman spectroscopy and Infrared Spectroscopy we probe the behavior of the hydrogen confined in these porous materials at high pressure by tracking changes in the in situ high pressure x-ray diffraction patterns and shifts in the hydrogen vibron peaks. [Preview Abstract] |
Wednesday, March 12, 2008 4:18PM - 4:30PM |
S36.00008: A combined pressure-temperature synthesis approach towards novel hydrogen storage materials Raja Chellappa, Maddury Somayazulu, Viktor Struzhkin, Russell Hemley There is a growing need to explore synthesis of novel hydrogen storage materials with very high hydrogen content ($>$ 30 wt.{\%}) as well as tuning materials in order to facilitate reversible hydrogen desorption and absorption. A combined pressure-temperature ($P-T)$ approach holds considerable promise towards achieving these objectives. In this talk, we will present results from our on-going efforts to synthesize hydrogen clathrates with very high hydrogen content that can be recovered at moderate $P-T$ conditions based on simple molecular systems including clathrates and van der Waals compounds, specifically H$_{2}$O, CH$_{4}$, NH$_{3}$, and boron containing systems. The use of suitable additives to enhance stability will also be explored. Results will also be presented from the direct $P-T$ synthesis of metastable light metal (Li, Mg, B- based) complex hydrides. [Preview Abstract] |
Wednesday, March 12, 2008 4:30PM - 4:42PM |
S36.00009: Structure of Nanoporous Biocarbon for Hydrogen Storage as Determined by Small Angle X-Ray Scattering Mikael Wood, J. Burress, J. Pobst, S. Carter, P. Pfeifer, C. Wexler, P. Shah, G. Suppes As a member of the Alliance for Collaborative Research in Alternative Fuel Technology (ALL-CRAFT) our research group studies the properties of nanoporous biocarbon, produced from waste corn cob, with the goal of achieving the Department of Energy's gravimetric and volumetric standards for both hydrogen and methane gas storage. Small Angle X-Ray Scattering (SAXS) is a valuable tool in our investigation of the geometry of the pore space in our carbon samples. In this talk, we will compare the experimental SAXS data with theoretical results for various pore geometries to determine which pore models are consistent with experiment. Using data from nitrogen adsorption isotherms, along with SAXS, yields significant structural information about the pore space. This analysis should allow us to fully optimize our production process and to achieve the DOE's target storage capacities. This work supported by: 1. National Science Foundation (PFI-0438469) 2. U.S. Department of Education (P200A040038) 3. U.S. Department of Energy (DE-AC02-06CH11357) 4. University of Missouri (RB-06-040) 5. U.S. Department of Defense (N00164-07-P-1306) 6. U.S. Department of Energy (DE-FG02-07ER46411) [Preview Abstract] |
Wednesday, March 12, 2008 4:42PM - 4:54PM |
S36.00010: High Capacity Hydrogen Storage on Nanoporous Biocarbon Jacob Burress, Mikael Wood, Michael Gordon, Phillip Parilla, Michael Benham, Carlos Wexler, Fred Hawthorne, Peter Pfeifer The Alliance for Collaborative Research in Alternative Fuel Technology (http://all-craft.missouri.edu) has been optimizing nanoporous biocarbon for high capacity hydrogen storage. The hydrogen storage was measured gravimetrically and volumetrically (Sievert's apparatus). These measurements have been validated by NREL and Hiden Isochema. Sample S-33/k, our current best performer, stores 73-91 g H$_{2}$/kg carbon at 77 K and 47 bar, and 1.0-1.6 g H$_{2}$/kg carbon at 293 K and 47 bar. Hydrogen isotherms run by Hiden Isochema have given experimental binding energies of 8.8 kJ/mol compared to the binding energy of graphite of 5 kJ/mol. Results from a novel boron doping technique will also be presented. The benefits and validity of using boron-doping on carbon will also be discussed. [Preview Abstract] |
Wednesday, March 12, 2008 4:54PM - 5:06PM |
S36.00011: Preparation and Cryogenic Hydrogen Storage Capacity of Nanoporous Carbon Materials Synthesized using an Aerosol-Assisted Approach Qingyuan Hu, Yunfeng Lu, Gregory P. Meisner Spherical nanoporous carbon particles were synthesized from carbon precursor solutions of sucrose with either silica sols, colloidal silica particles, or both, in a direct one-step aerosol-assisted process, followed by carbonization and then removal of the silica template. The resulting particles show very high porosity with narrow pore size distributions, surface areas up to 2000~m$^{2}$/g, and pore volumes up to 4.0~cm$^{3}$/g. The porosity and pore sizes depend on the type and amount of silica template precursor added to the sucrose precursor solutions. The carbon particles were characterized by transmission electron microscopy, field emission scanning electron microscopy, and nitrogen sorption surface area measurements. Hydrogen adsorption was measured at various temperatures between 77 K and room temperature and at pressures up to 50 bars. The maximum hydrogen uptake of up to 4.0~wt{\%} at 77~K and $>$20~bar was found for nanoporous carbon particles made using the silica sol template. [Preview Abstract] |
Wednesday, March 12, 2008 5:06PM - 5:18PM |
S36.00012: NMR Characterization of Hydrogen Adsorption and Pore Structures of Carbon-Based Materials B.J. Anderson, Alfred Kleinhammes, Yue Wu Hydrogen adsorption in carbon-based materials such as boron-doped graphite and carbon aero gels were investigated by nuclear magnetic resonance (NMR). $^{1}$H NMR is shown to be a sensitive and quantitative probe for detecting adsorbed gas molecules such as H$_{2}$, methane, and ethane. NMR measurements were carried out in-situ under given H$_{2}$ pressure up to a pressure of over 100 atm, at room temperature and 100 K. From such $^{1}$H NMR measurement, the amount of adsorbed H$_{2}$ molecules was determined versus pressure. In addition to measuring adsorption binding energies via isotherms, the structure and distribution of the nanopores within the material were characterized in order to relate the size of the pores to the rate of diffusion of the H$_{2}$ to the adsorption sites. [Preview Abstract] |
Wednesday, March 12, 2008 5:18PM - 5:30PM |
S36.00013: Fabrication Procedures and Material Properties of Activated Carbon for Hydrogen and Methane Storage Jeffrey Pobst, Jacob Burress, Mikael Wood, Matthew Beckner, Parag Shah, Michael Gordon, Phillip Parilla, Sarah Barker, Sara Carter, Lauren Aston, Galen Suppes, Peter Pfeifer The Alliance for Collaborative Research in Alternative Fuel Technology (http://all-craft.missouri.edu) has developed nanoporous biocarbons with interesting pore characteristics. These carbons are being optimized for hydrogen and methane vehicular storage. Our current best performer stores 73-91 g H$_{2}$/kg carbon at 77 K and 47 bar, and 1.0-1.6 g H$_{2}$/kg carbon at 293 K and 47 bar. The validity of using methane storage as a predictor for hydrogen storage will be presented. Recent carbons have achieved porosities as high as of 0.8 and BET surface areas of 3,500 m$^{2}$/g. Optimal pore sizes and volumes will be presented for hydrogen storage nanoporous carbon. [Preview Abstract] |
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