Bulletin of the American Physical Society
2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009; Pittsburgh, Pennsylvania
Session Q28: Focus Session: Hydrogen Storage/Nanomaterials for Energy |
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Sponsoring Units: DMP Chair: Jason Graetz, Brookhaven National Laboratory Room: 330 |
Wednesday, March 18, 2009 11:15AM - 11:51AM |
Q28.00001: Carbon Dioxide Capture in Microporous Metal-Organic Frameworks Invited Speaker: Metal-organic frameworks represent a new class of materials exhibiting high internal surface areas, tunable pore dimensions, and tailorable surface functionality. Research in our laboratory has focused on the development of metal-organic frameworks with surfaces bearing open metal coordination sites for high-enthalpy hydrogen adsorption. Recently, we have initiated efforts to utilize such materials for the selective capture of CO$_{2}$ from flue gas. Here, open metal coordination sites can deliver a high CO$_{2}$ loading capacity at low pressures. However, additional criteria, such as water stability and the selective binding of CO$_{2}$ over N$_{2}$, must also be taken into consideration. Towards that end, we have targeted air- and water-stable frameworks bearing surfaces coated with amine groups. For example, the use of 1,3,5-benzenetristriazolate (BTTri$^{3-})$ as a bridging ligand has led to sodalite-type frameworks such as HCu[(Cu$_{4}$Cl)$_{3}$(BTTri)$_{8}$], possessing open Cu$^{2+}$ coordination sites and exhibiting good chemical and thermal stability. Attachment of ethylenediamine to the Cu$^{2+}$ sites within this structure generates a material that selectively binds small amounts of CO$_{2}$ over N$_{2}$. Details of the characterization of this and related materials will be presented. [Preview Abstract] |
Wednesday, March 18, 2009 11:51AM - 12:03PM |
Q28.00002: Hydrogen storage in a metal-organic-framework structure from a nonempirical van der Waals density functional approach Lingzhu Kong, Valentino C. Cooper, Nour Nijem, Yves J. Chabal, KunHao Li, Jing Li, David C. Langreth Hydrogen adsorption in the metal-organic-framework structure Zn$_2$(BDC)$_2$(TED) (BDC=benzenedicarboxylate; TED=triethylenediamine) is studied using a van der Waals-density-functional approach.\footnote{M. Dion et al., PRL {\bf 92}, 246401 (2004); T. Thonhauser et al., PRB {\bf 76}, 125112 (2007).} Two types of adsorbtion sites are located in the structure. The binding energies and the number of such sites are in good agreement with the values obtained from the experimental isotherms and isosteric heat of adsorption.\footnote{J.Y. Lee et al., Adv. Func. Mater. {\bf 17}, 1255 (2007).} The stretching mode frequency of the adsorbed H$_2$ is calculated for various H--H bond orientations at the two positions. The frequency changes by approximately $-30$ cm$^{-1}$ for the strongest binding direction at each of the two points, which is consistent with the measured infrared absorption band measured at 4120 cm$^{-1}$ at room temperature and high pressures (300-800 psi). [Preview Abstract] |
Wednesday, March 18, 2009 12:03PM - 12:15PM |
Q28.00003: Enhanced H$_{2}$ adsorption in metal-organic frameworks with open metal sites: Binding mechanism and strong dependence on metal ions Wei Zhou, Hui Wu, Taner Yildirim Metal-organic frameworks (MOFs) with open metal sites exhibit much stronger H$_{2}$ binding strength than classical MOFs, due to the direct interaction between H$_{2}$ and the coordinately unsaturated metal ions. [1] Here we will present a systematic study of the H$_{2}$ adsorption on a series of isostructural MOFs, M$_{2}$(dhtp) with open metals M = Mg, Mn, Co, Ni, Zn. The experimental, initial isosteric heats of adsorption for H$_{2}$ ($Q_{st})$ of these MOFs range from 8.5 to 12.9 KJ/mol, with increasing $Q_{st}$ in the following order: Zn, Mn, Mg, Co, and Ni.[2] The H$_{2}$ binding energies derived from first-principles calculation follow the same trend as the experimental observation on $Q_{st}$, confirming the electrostatic Coulomb attraction between the H$_{2}$ and the open metals being the major interaction. We also found a strong correlation between the metal ion radius, the M-H$_{2}$ distance and the H$_{2}$ binding strength, which provides a viable, empirical method to predict the relative H$_{2}$ binding strength of different open metals. [1] J. Phys. Chem. C, 112, 8132 (2008). [2] J. Am. Chem. Soc., 130, 15268 (2008). [Preview Abstract] |
Wednesday, March 18, 2009 12:15PM - 12:27PM |
Q28.00004: Noncovalent hydrogen bonding in metal-organic structures Norm M. Tubman, Jonathan L. Dubois, Randolph Q. Hood, Sebastien Hamel, Eric R. Schwegler Transition metal sites in metal-organic frameworks and in doped carbon structures are actively being studied for their binding properties of molecular hydrogen. We present a study of prototypical metal-organic structures that can be used to bind molecular hydrogen non-covalently. Due to the well known limitations of current density functional theory based descriptions of non-covalent hydrogen bonding we have focused our efforts on a consistent many-body approach based on the fixed-node diffusion Monte Carlo method. Accurate studies of binding energies and the effects of multiple hydrogens in these structures are presented. Prepared by LLNL under Contract DE-AC52-07NA27344 [Preview Abstract] |
Wednesday, March 18, 2009 12:27PM - 12:39PM |
Q28.00005: Pd-assisted hydrogen spillover on graphene and carbonanotubes Sa Li, Puru Jena Addition of a small amount of Pd precursors on carbon nanotubes has recently been found to substantially improve the hydrogen uptake. In spite of several attempts, a fundamental understanding of how the catalyst works has remained unattainable. Using first principles methods we have investigated hydrogen spillover on Pd-doped graphene and (8,8) carbon nanotube. Through molecular dynamics (MD) simulations, we found that each Pd can bind to three pairs of hydrogen molecules on graphene and only one pair of hydrogen molecule on (8,8) nanotube at 300K. This difference is attributed to the effect of curvature. The hydrogen molecules were found to dissociate and bind to carbon surface once the Pd atom is saturated with hydrogen. These results provide important new insight to understand hydrogen spillover on carbon based materials. [Preview Abstract] |
Wednesday, March 18, 2009 12:39PM - 12:51PM |
Q28.00006: Calcium-Decorated Carbon Nanotubes for Hydrogen Storage Hoonkyung Lee, Jisoon Ihm, Marvin L. Cohen, Steven G. Louie Using the first-principles pseudopotential density-functional method, we carry out a systematic search for high-capacity hydrogen storage media based on individually dispersed calcium atoms on carbon nanotubes (CNTs). We find that Ca clustering is suppressed on boron-doped and defective carbon nanotubes and that up to six H$_{2}$ molecules can bind to a Ca atom with a binding energy of $\sim $0.2 eV/H$_{2}$. We show that Ca-decorated CNTs with a concentration of $\sim $6 at. {\%} B doping can reach the gravimetric capacity of $\sim $5 wt {\%} hydrogen storage. We also will discuss the binding mechanism of the H$_{2}$ molecules. [Preview Abstract] |
Wednesday, March 18, 2009 12:51PM - 1:03PM |
Q28.00007: Theoretical study of hydrogen storage in Ca-coated fullerenes Qiang Sun, Qian Wang, Yoshi Kawazoe, Puru Jena First principles calculations based on gradient corrected density functional theory and molecular dynamics simulations of Ca decorated fullerene yield some novel results: (1) C60 fullerene decorated with 32 Ca atoms on each of its 20 hexagonal and 12 pentagonal faces is extremely stable. Unlike transition metal atoms that tend to cluster on a fullerene surface, Ca atoms remain isolated even at high temperatures. (2) C60Ca32 can absorb up to 62 H2 molecules in two layers. The first 30 H2 molecules dissociate and bind atomically on the 60 triangular faces of the fullerene with an average binding energy of 0.45 eV/H, while the remaining 32 H2 molecules bind on the second layer quasi-molecularly with an average binding energy of 0.11 eV/H2. These binding energies are ideal for Ca coated C60 to operate as a hydrogen storage material at near ambient temperatures with fast kinetics. (3) The gravimetric density of this hydrogen storage material can reach 5.8 wt {\%}. Simple model calculations show that this density is the limiting value for higher fullerenes. [Preview Abstract] |
Wednesday, March 18, 2009 1:03PM - 1:15PM |
Q28.00008: Rotor in a Cage: Infrared Spectroscopy of an Endohedral Hydrogen-Fullerene Complex Toomas R{\~o}{\~o}m, Min Ge, D. H{\"u}vonen, U. Nagel, S. Mamone, A. Danquigny, F. Cuda, M. C. Grossel, M. Carravetta, M. H. Levitt, Y. Murata, K. Komatsu We report the observation of quantized translational and rotational motion of molecular hydrogen inside the cages of C$_{60}$. Narrow infrared absorption lines at the temperature of 6\,K correspond to vibrational excitations in combination with translational and rotational excitations and show well-resolved splittings due to the coupling between translational and rotational modes of the endohedral H$_2$ molecule. A theoretical model shows that H$_2$ inside C$_{60}$ is a three-dimensional quantum rotor moving in a nearly spherical potential. The theory provides both the frequencies and the intensities of the observed infrared transitions. Good agreement with the experimental results is obtained by fitting a small number of empirical parameters to describe the confining potential, as well as the {\it ortho\/} to {\it para\/} ratio at 6\,K and at elevated temperatures [S. Mamone, et al., arXiv:0807.1589v2]. [Preview Abstract] |
Wednesday, March 18, 2009 1:15PM - 1:27PM |
Q28.00009: Hydrogen storage in charge compensated organic molecular crystals Mina Yoon, Matthias Scheffler We propose charge compensated organic molecular crystals as a promising class of materials for hydrogen storage. Using quantum mechanical first-principles calculations based on numerical atom-centered orbitals as all-electron basis functions [1] we study the basic structural properties of molecular crystals consisting of parallel sheets of cations and anions (such as DMPH and TCNQ) stacked alternatingly. The long range dispersion interactions between the cations and anions, which are important for the stability of the crystals, were studied and compared using various DFT xc functionals, semi- empirical approach [2], and M\o ller-Plesset perturbation theory. The molecular configuration causes accumulation of electrons at acceptors and depletion at donors, which results in finite dipolar fields. Our study indicates that these fields make it possible to use charge compensated organic molecular crystals for hydrogen storage. \\[3pt] [1] V. Blum {\it et al}., FHI ab initio molecular simulations (FHI-aims) project.\\[0pt] [2] A. Tkatchenko and M. Scheffler, to be published. [Preview Abstract] |
Wednesday, March 18, 2009 1:27PM - 1:39PM |
Q28.00010: Mg-doped GaN nanostructures: Energetics, magnetism and H2 adsorption Qian Wang, Qiang Sun, Puru Jena It has been shown that p-type GaN can greatly improve the performance of GaN-based devices. Mg is a suitable candidate dopant for p-type GaN. Since the ionic radius of Mg is comparable with that of Ga, Mg doping can be expected to eliminate self-compensation effects. Thus, synthesis of Mg-doped p-type GaN for fabrication of optoelectronic devices has been hotly pursued. Using density functional theory and generalized gradient approximation for exchange and correlation potential we show that Mg doped GaN nanocage and nanotube can be magnetic with Mg contributed spins distributed over the neighboring N sites. Mg atoms show no tendency for clustering and due to the positive charge residing on them; they can trap hydrogen in molecular form via the charge polarization mechanism. The binding energies of hydrogen lie in the range of 0.1$\sim $0.2 eV/H2 which are ideal for storage applications under ambient thermodynamic conditions. [Preview Abstract] |
Wednesday, March 18, 2009 1:39PM - 2:03PM |
Q28.00011: The USDOE Hydrogen Program: Status and Performance Gaps of On-board Hydrogen Storage Technologies Grace Ordaz, Monterey Gardiner, Carole Read, Ned Stetson The USDOE Hydrogen Program's mission is to reduce oil use and carbon emissions in the US transportation sector and to enable clean, reliable energy for stationary and portable power generation. The requirements for vehicular hydrogen storage continue to be one of the most technically challenging barriers to the widespread commercialization of hydrogen fueled vehicles. The DOE applied hydrogen storage activity focuses primarily on the research and development of low-pressure, materials-based technologies to allow for a North American market driving range of more than 300 miles (500 km) while meeting packaging, cost, safety, and performance requirements to be competitive with current vehicles. This presentation summarizes the status, recent accomplishments and current performance gaps of hydrogen storage technologies primarily for transportation applications. Materials projects are focused in three main areas: metal hydrides, chemical hydrogen storage materials, and hydrogen sorbents. A new effort is the Hydrogen Storage Engineering Center of Excellence which will provide a coordinated approach to the engineering research and development of on-board storage and refueling systems. The presentation will especially highlight topics emphasized in the session theme. [Preview Abstract] |
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