Symposium OrganizersEric Majzoub, University of Missouri, St. Louis
Jason Graetz, Brookhaven National Laboratory
Vidvuds Ozolins, University of California, Los Angeles School of Engineering and Applied Sciences
Petra de Jongh, Utrecht University
P2: Carbon Capture Overview
Tuesday PM, April 10, 2012
Moscone West, Level 2, Room 2022
2:30 AM - *P2.1
Carbon Dioxide Capture in Metal-organic Frameworks
Thomas M McDonald 1 Zoey R Herm 1 Eric D Bloch 1 Kenji Sumida 1 2 Jarad A Mason 1 2 Jeffrey R. Long 1 2
1University of California, Berkeley Berkeley USA2Lawrence Berkeley National Laboratory Berkeley USAShow Abstract
Efforts to utilize metal-organic frameworks, a new class of materials exhibiting high surface areas, tunable pore dimensions, and tailorable surface functionality, for CO2 capture will be presented. Open metal coordination sites on the framework surface can deliver a high CO2 loading capacity at low pressures. However, additional criteria, such as water stability and the selective binding of CO2 over N2, must also be considered. Towards that end, we have targeted air- and water-stable frameworks bearing surfaces coated with alkylamine groups. Use of 1,3,5-benzenetristriazolate (H3BTTri) as a bridging ligand has led to sodalite-type frameworks of the type M3[(M4Cl)3(BTTri)8]2, possessing open M2+ coordination sites and exhibiting good chemical and thermal stability. Attachment of ethylenediamine to the M2+ sites within this structure can generate a material that selectively binds CO2 over N2. In addition, the application of frameworks with redox-active transition metal sites for the capture of O2 from air will be discussed.
3:00 AM - P2.2
Effects of Pore Polarizability on the Interactions between Weakly Interacting Gases and Metal-organic Frameworks
Scott T Meek 1 John J Perry 1 Stephanie L Teich-McGoldrick 2 Jeffery A Greathouse 2 Mark D Allendorf 1
1Sandia National Laboratories Livermore USA2Sandia National Laboratories Albuquerque USAShow Abstract
Metal-organic frameworks (MOFs), hybrid lattices of metal ions and organic electron donors, have received considerable attention for the storage of hydrogen and other light gases due to their high surface areas and tailorable structures. The synthetic flexibility of these compounds makes them ideal candidates for systematically probing the influence of specific structural attributes, such as chemical functionality, surface area, and pore size and shape, on gas adsorption. Thus far, however, the influence of pore polarizability in tuning gas-MOF interactions has not been extensively explored. To this end, we prepared a complete series of halogenated MOFs with the isoreticular (IRMOF) topology. Derivatives of the IRMOF-1 structure in which one hydrogen is substituted with â?"F, -Cl, -Br, and â?"I were synthesized, and adsorption isotherms for these materials for a variety of weakly interacting gases, including hydrogen were measured. We find that, as the polarizability of the linker increases with the size of the halogen, uptake of light gases increases. Activation procedures were also investigated in detail and were shown to strongly influence gas sorption. The best activation procedures yield pore volumes and gas uptake consistent with those predicted by atomistic modeling.
3:15 AM - P2.3
MOF for CO2 Sequestration
May Ling Ng 1 Gregory T Carroll 1 Stephen T Kelly 1 Andrey Shavorskiy 1 Pascal A Nigge 1 Hendrik Bluhm 1 Mary K Gilles 1
1Lawrence Berkeley National Laboratory Berkeley USAShow Abstract
A porous metal organic framework (MOF) is a promising material for gas capturing and storage. [1-3] For instance, MOF can be used for CO2 sequestration [2, 4], i.e. for capturing, storage and conversion of CO2 to an environmentally more acceptable substance. There are many uptake experiments performed on various types of MOFs but very few of them study the uptake sites of the gas molecules on the MOF structure in a realistic ambient environment. This knowledge is essential for optimizing the functionality of MOFs, e.g. by knowing the exact CO2 binding sites on MOF, we can design the uptake sites to release the captured molecules. By identifying the physical and chemical stability of the MOF system, we can manipulate these factors to our benefi t such as to harvest the captured gas from the framework. We have synthesized a MOF that is deposited on a Si wafer to enable characterization with surface science techniques. Our first objective is to study CO2 uptake in the MOF at ambient pressure by photoelectron spectroscopies. As a proof of concept, we hope to capture CO2 with the MOF. Our preliminary photoemission spectroscopic (PES) results show a drastic but systematic change between the C 1s spectra taken from a MOF before, during and after CO2 uptake. The changes may represent a profound CO2 uptake in the MOF. In addition, the MOF C 1s pro file takes a long time to recover to its original state as in before CO2 uptake. This implies that the captured CO2 in the framework is stable. Most interestingly, the uptake occurs at room temperature and without any chemical assistance. References  O. M. Yaghi, M. O'Keeffe, N. W. Ockwig, H. K. Chee, M. Eddaoudi, J. Kim, Nature, 2003, Vol. 423, 705.  D. Britt, D. Tranchemontagne, O. M. Yaghi, PNAS, 2008, vol. 105, no. 33, 11623.  U. Mueller, M. Schubert, F. Teich, H. Puetter, J. Schierle-Arndt, J. PastrÃ©, J. Mater. Chem., 2006, 16, 626.  A. R. Millward, O. M. Yaghi, J. Am. Chem. Soc., 2005, 127, 17998.
4:00 AM - P2.4
Tuning Programmable Polymers for Reversible CO2 Sequestration
Dara Gough 1 Bruce Bunker 1 Dale Huber 1 Erik Spoerke 1
1Sandia National Labs Albuquerque USAShow Abstract
Programmable polymers are under development to promote the reversible capture and release of CO2 from aqueous solutions. The mechanism for reversible CO2 sequestration in water involves the conversion of relatively insoluble CO2 into soluble bicarbonates for capture and the conversion of bicarbonates back to CO2 for release. Such conversions can be stimulated by switching the solution pH, by use of a programmable polymer alone or such a polymer in the presence of enzymes such as carbonic anhydrase. The programmable polymers that we are investigating involve either poly(n-isopropylacrylamide) (PNIPAM) or the polypeptide elastin that are modified to contain acid groups such as carboxylic acids. Programming is achieved by changing the solution temperature to promote a reversible phase transition. Below the transition, the acid groups find themselves in a hydrophilic environment that promotes acid dissociation and the generation of an acidic solution pH. Above the transition, the acid groups find themselves in a hydrophobic environment that leads to protonation of the polymer and the generation of a basic solution pH. We have found that with a copolymer of PNIPAM and polyacrylic acid (PAA), we can change the pKa of the polymer by over 5 units, which is sufficient for both CO2 loading and unloading processes. This paper describes the range of variations we have explored in polymer composition to control: the transition temperature, the magnitude of the pKa change, the pH range over which programming occurs, the use of electric fields to stimulate programming, and tethering of the polymer to a support that would be suitable for deployment in a large scale process. We find that optimization of polymer performance is controlled by tuning the relative concentrations of hydrophobic and hydrophilic groups on the polymer chains. Implication of the results on large-scale CO2 sequestration processes will be discussed. This work was supported by the Laboratory Directed Research and Development program at Sandia National Laboratories. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energyâ?Ts National Nuclear Security Administration under contract DE-AC04-94AL85000.
4:15 AM - P2.5
Design and Evaluation of the Canopy Configurations of Liquid-like Nanoparticle Organic Hybrid Materials for CO2 Capture
Camille Petit 1 Youngjune Park 1 Andrew Kun-Yi Lin 1 Ah-Hyung Alissa Park 1
1Columbia University New York USAShow Abstract
The field of hybrid materials has recently seen the emergence of a new class of nanomaterials referred to as Nanoparticle Organic Hybrid Materials (NOHMs). These inorganic-organic materials consist of polymer chains (canopy) grafted onto an inorganic nanoparticle (core), and can exhibit liquid-like behavior in the absence of solvent. Owing to their negligible vapor pressure and great thermal stability, which represent significant advantages compared to the widely used amine solvents, NOHMs appear to be promising candidates for CO2 capture. These materials can absorb CO2 via an enthalpic effect related to the tunable chemistry of the canopy with proper selection of task-specific groups (e.g., amine), as well as an entropic effect arising from the â?ofrustratedâ? structural arrangement of the polymer chains. In this study, silica nanoparticle-based NOHMs with various canopy configurations were synthesized and characterized before and after exposure to CO2 using NMR, Raman, and ATR FT-IR spectroscopies in order to investigate the effect of the grafting densities and polymer chain configurations (linear vs branched) on the NOHM canopy structure as well as CO2 capture behavior. Moreover, the impact of N2, SO2 and H2O, three species also present in the flue gas, on CO2 capture was analyzed using a high pressure reactor. The results indicate that the canopy species can be â?ofrustratedâ? which translates into a greater ordering and alignment of the polymer chains compared to the bulk polymer. This effect allows the formation of â?ounoccupiedâ? space or favorable â?opathwaysâ? for CO2 to be absorbed. It also enables a reduction in CO2-induced swelling as well as a distinct CO2-packing behavior compared to the unbound polymer. All these phenomena can be tuned through the variation of the grafting density and/or the polymer chains configuration. In addition, the materials benefit from a very good selectivity towards CO2 relative to N2. On the other hand, the impact of H2O and SO2 on the CO2 capture capacity is dependent on the type of NOHMs.
4:30 AM - P2.6
Probing CO2 Sorption on Hyperbranched Aminosilica with NEXAFS
Laura Espinal 1 Martin L Green 1 Cherno Jaye 1 Daniel A Fischer 1 Watcharop Chaikittisilp 2 Christopher W Jones 2
1NIST Gaithersburg USA2Georgia Institute of Technology Atlanta USAShow Abstract
Traditional technologies for capturing CO2 from flue gas streams involve the use of the aqueous amine technology, which is an energy intensive process due to the high heat capacity of water and need for heating to regenerate the solvent (CO2 desorption). As alternative technologies, several solvent-free approaches based on solid sorbents have been proposed to capture CO2 emissions. In particular, amine-modified silica materials have great potential as temperature swing CO2 sorbents from postcombustion flue gas because of their inherent ability to selectively adsorb CO2 over N2 at atmospheric pressures. Within this class of materials, hyperbranched aminosilicas (HAS) â?" in which the aminopolymers are polymerized in situ within the mesoporous silica support â?" have recently gained attention due to their high amine loading, large CO2 capacity, and demonstrated multicycle stability. However, experimental insights on the nature of the amine-CO2 interaction at molecular level remain largely unexplored. Understanding the molecular level interactions is critical for further improving the material design. We have used near edge X-ray absorption fine structure (NEXAFS) spectroscopy to probe the surface state of adsorbed CO2 on an HAS material. An overview of the NEXAFS technique will be presented highlighting the utility of the environmental chamber externally attached to the NEXAFS endstation to allow for sample heating, cooling, and CO2 dosing immediately prior to NEXAFS analysis. We will present the NEXAFS analysis of an HAS material before and after sample dosing with CO2 based on data recorded in the spectral region close to the C, N, and O K absorption edges (from. 250 to 590 eV).
4:45 AM - P2.7
A Study of MgO Aerogels for CO2 Capture
Joshua Wilson 1 Tanya Faltens 1 Mingheng Li 1 Winny Dong 1
1Cal Poly Pomona Pomona USAShow Abstract
CO2 capture on solid sorbents is an important technique in the context of greenhouse gas emission reduction as well as adsorption enhanced reaction processes. Traditional CO2 adsorbents such as hydrotalcites, alumina and zeolite have been extensively investigated. This work will focus on the study of CO2 adsorption on sol-gel derived MgO aerogels, which could have a great potential because of their large surface area (~ 500 m2 g-1). In this study amorphous MgO aerogels were compared with Alumina, crystalline (low surface area) MgO, and amorphous MgO xerogels. A thermogravimetric analyzer (TGA) was employed where the weight gain of the sample due to CO2 adsorption was measured. CO2 was introduced at different partial pressures starting from 0.0204 atm and going on to 0.0417 atm, 0.0638 atm, 0.087 atm, 0.111 atm, 0.5 atm, and finally 1 atm. Adsorption isotherms and the adsorption capacity of each material were determined. Data showed that the adsorption capacity of the MgO aerogel at 1 atm partial pressure of CO2 was 0.314 mmol CO2/g adsorbent. This was more than twice the CO2 capacity of the next highest adsorbent. It was also observed that MgO aerogel has faster CO2 adsorption kinetics and is less prone to N2 adsorption as compared to Alumina. The CO2 capacity was correlated to surface area, porosity, and structure.
5:00 AM - P2.8
Carbon Storage Properties of OMS-2 Manganese Oxide
Lan Li 1 Eric J Cockayne 1 Laura Espinal 1 Winnie Wong-Ng 1
1National Institute of Standards and Technology Gaithersburg USAShow Abstract
The manganese oxide OMS-2 (Octahedral Molecular Sieve) material, also known as Î±-MnO2, is of great interest for carbon storage applications. Our experiments show that OMS-2 exhibits CO2 sorption hysteresis at pressures larger than 7 bar. The hysteretic behavior is strongly dependent on time, temperature and pressure. To better understand the atomic structures and sorption mechanism we have performed first-principles total energy calculations. OMS-2 materials have (2Ã-2)+(1Ã-1) tunnel structures, built from chains of edge-sharing MnO6 octahedra. The small (1Ã-1) tunnel is empty while the large (2Ã-2) tunnel contains additional species, such as K+ and H2O, to stabilize the structure. Our first-principles calculations indicate that the binding energy of H2O in the OMS-2 is 0.39eV, smaller than that of K+ by 4eV, and that therefore H2O can be easily removed from the OMS-2, but K+ remains. We find that K+ behaves as a â?ogate keeperâ?, which blocks the diffusion of CO2 in the OMS-2 due to high energy barrier (5.44eV/CO2 molecule). Increasing the concentration of CO2 can dramatically lower the energy barrier for CO2 to bypass K+. The gate-keeping behavior accounts for the observed sorption hysteresis. Based on the experimental and computational results, a possible CO2 sorption mechanism by OMS-2 will be discussed.
5:15 AM - P2.9
Amorphous Mg-Al Mixed Oxide Materials Modified by Phosphorus Anion for CO2 Adsorption
Hyuk Jae Kwon 1 Jeong Gil Seo 1 Soonchul Kwon 1 Hyun Chul Lee 1
1Samsung Advanced Institute of Technology Yongin-si Republic of KoreaShow Abstract
Since carbon dioxide (CO2) is recognized as greenhouse gas, advanced technologies for removing CO2 from the flue gas stream of power plants have been intensively developed. Among several different approaches to capture CO2, adsorption using solids is one of the most promising technologies to achieve lower energy demands or energy penalties. It is well known that amorphous Mg-Al mixed oxides have a larger surface area and good stability at high temperature. Heteroelement or anion including P, S, O and F plays an important role of creation of basic active site (basicity) or increase of polarity leading to stronger attraction of CO2 on the surface. In the study, development of phosphorus modified-MgAlOx for CO2 adsorption was clearly described with the synthesis method and the direct observation results by characterization study. Quantum calculation by using density function theory (DFT) was introduced to understand CO2 adsorption mechanism. MgAlOx and P-MgAlOx materials have been prepared by co-precipitation and ion-exchange methods. Co-precipitation method for preparation of hydrotalcite-like compounds (HTCs) reported in the literature. As-prepared HTCs have been ion-exchanged with aqueous solution of phosphorus salt at room temperature for 1day. The resultants were washed and dried. Finally all of the resultants were calcined at 400 oC for 5h to derive the corresponding mixed oxides. The characterization of synthesized sorbents was analyzed by ICP-AES, XRD, TEM, and N2 adsorption and desorption. In addition, CO2 adsorption was estimated as both total CO2 capacity and 90% breakthrough CO2 capacity. The CO2 activity has been examined over a packed-bed flow reactor system employed sorbent of 25mg under adsorption condition of 10 vol.% CO2 in balance N2. Each test run was carried out at 200 to 400 oC at atmospheric pressure. The density function theory (DFT) calculations with GGA-PBE functional were performed to determine adsorption energies and electronic properties including density of states and Mulliken population analysis of the interaction between the adsorbed CO2 molecules and the surface of sorbents in the three dimensional periodic-slab models. Geometry optimizations were reliably carried out using DMol3. The XRD patterns of as-prepared HTCs revealed the layered structure with the present of nitrate and phosphate in the interlayer. After calcinations, XRD patterns and TEM image for P-MgAlOx indicated the typical amorphous mixed oxide structure which results in a larger surface area and good thermal stability. From the results, prepared P-MgAlOx showed superior CO2 adsorption capacity. It is due to formation of amorphous structure and exchanged high P contents with basic active sites for CO2 adsorption. In addition, the other characterizations to determine material properties, CO2 adsorption and cyclic study, and Quantum calculations with density function theory (DFT) will be also evaluated and discussed in the present study.
5:30 AM - P2.10
Graphene Oxide Based High-surface Area NanoPorous Materials for Hydrogen Storage and Carbon Capture
Srinivas Gadipelli 1 2 Jacob Burress 1 Taner Yildirim 1 2
1National Institute of Standards and Technology Gaithersburg USA2University of Pennsylvania Philadelphia USAShow Abstract
Even though there has been extensive research on gas adsorption properties of various carbon materials based on activated carbon, nanotubes, and graphite/graphene, there has been little work done on the gas adsorption properties of graphite oxide (GO). In this study, we show that one-and-a-half-century-old graphite oxide can be easily turned into a potentially useful gas storage material. In order to create high-surface nanoporous materials from GO, we used two different approaches. In the first approach, we have successfully synthesized graphene-oxide framework materials (GOFs) by interlinking GO layers by diboronic acids. The resulting GOF materials have well defined pore size and BET surface area up to 500 m2/g with twice larger heat of adsorption of H2 and CO2 than those found in other physisorption materials such as MOF5. In the second approach, we synthesized a range of high surface area GO derived activated carbons (AGs) and studied their applications toward high pressure CO2 and CH4 gas storage. The AGs, with wide range of pore structure, have been prepared by chemical activation with potassium hydroxide (KOH). We obtain largely increased surface areas up to nearly 1900 m2/g for AG samples from 10 m2/2 for initial GO. Increase in activation temperature and KOH concentration leads to an increase in pore volume and pore width. A detailed experimental study of high pressure excess sorption isotherms on AGs reveal an increase in both CO2 and CH4 storage capacities compared to other high surface area activated carbons. Finally, we compared the gas sorption properties of our GO-based matarials with other physisorption materials such as MOFs, ZIFs, and COFs.
5:45 AM - P2.11
Atmospheric Carbon Dioxide Capture Using Zeolites
Nicholas R Stuckert 1 Ralph T Yang 1
1University of Michigan Ann Arbor USAShow Abstract
Carbon dioxide capture is fast becoming a necessity. Only two thirds of CO2 is produced at large stationary sources. To this end, capture from the atmosphere and concentration by cyclic adsorption-desorption processes are studied for the first time. Zeolites of type X are compared with different cations, and the effect of the alumina to silica ration is explored. Breakthrough performance showed low silica type X (LSX) capable of gas hourly space velocities of at least 63,000 hr-1. When compared with amine based adsorbents we find that the uptake rate is as important as the cyclic capacity. Li-LSX was found to have double the capacity of zeolite NaX at atmospheric conditions, which is higher than all other reported zeolites. Using a combined temperature and vacuum swing cycle, the CO2 concentration in the desorption product reaches >90%. This is the first report of a single cycle atmospheric CO2 capture system achieving a sequestration ready concentration of CO2.
P1: Hydrogen Storage Overviews
Tuesday AM, April 10, 2012
Moscone West, Level 2, Room 2022
9:00 AM - *P1.1
Remaining Challenges in Hydrogen Storage for Transportation
Scott W Jorgensen 1
1General Motors Warren USAShow Abstract
Todayâ?Ts impressive progress in the capacity of hydrogen storage materials and the capabilities of hydrogen storage systems is the result of world-wide interest and significant research funding over the last decade. In that time, a hydrogen and fuel cell economy has made some first steps forward, primarily in stationary and indoor applications. Despite this progress, world governments have elected to switch their focus to battery powered or battery assisted vehicles. That change reflects both political needs and technical judgments. A look back at what has been accomplished in hydrogen storage and what is left to do provides a reference frame for further commercialization and the research that will enable it.
9:30 AM - *P1.2
Methodology of Materials Discovery in Complex Metal Hydrides Using Experimental and Computational Tools
Ewa Ronnebro 1 Eric H Majzoub 2
1Pacific Northwest National Laboratory Richland USA2University of Missouri St. Louis USAShow Abstract
We present a review of the experimental and theoretical methods used in the discovery of new metal-hydrogen materials systems for hydrogen storage applications. The focus is on a specific subset of successful methods utilizing theoretical crystal structure prediction methods, computational approaches for screening large numbers of compounds, and medium-throughput experimental methods for the preparation of such materials. Monte Carlo techniques paired with a simplified empirical Hamiltonian provide crystal structure candidates that are refined using Density Functional Theory. First-principle methods using high-quality structural candidates are further screened for an estimate of reaction energetics, decomposition enthalpies, and determination of reaction pathways. Experimental synthesis utilizes a compacted-pellet sintering technique under high-pressure hydrogen at elevated temperatures. Crystal structure determination follows from a combination of Rietveld refinements of diffraction patterns and first-principles computation of total energies and dynamical stability of competing structures. The methods presented within are general and applicable to a wide class of materials for energy storage.
10:00 AM - *P1.3
Transition between Bonding States of Hydrogen in Hydrides
Shin-ichi Orimo 1
1Tohoku University Sendai JapanShow Abstract
Recently we are focusing on â?otransitionâ? between bonding states of hydrogen in hydrides. An example was found in CaPd hydride, that is, the hydride showed the multimode reversible hydriding/dehydriding reactions over a wide temperature range . At lower temperatures below 523 K, hydrogen solutes into a complex hydride CaPdH2.0 with [PdH2]2- complex anion to form a perovskite-type hydride CaPdH2.4, and then dissolutes from CaPdH2.4 to reform CaPdH2.0. At higher temperatures over 523 K, on the other hand, the complex hydride CaPdH2.0 decomposes into CaPd2 and CaH2, which recombines into CaPdH2.0. Another example was found in YMn2 hydride, that is, the hydride showed the continuous transformation from a metal hydride YMn2H4.5 to a complex hydride YMn2H6 with [MnH6]5- complex anion, even under 5 MPa of hydrogen at 423 K . The related studies will provide us a new guideline for designing advanced hydrogen storage materials.  K. Ikeda, N. Okuda, K. Ohoyama, H.-W Li, H.T. Takeshita, T. Otomo S. Orimo, Chem. Commun. 46, 8380 (2010).  M. Matsuo, K. Miwa, S. Semboshi, H.-W. Li, M. Kano, and S. Orimo, Appl. Phys. Lett. 98, 221908 (2011).
10:30 AM - P1.4
Room Temperature High-pressure Storage of Molecular Hydrogen in Porous Carbon
John Vajo 1 Robert W Cumberland 1 Wen Li 1 Cunman Zhang 3 2 Mei Cai 2
1HRL Laboratories Malibu USA2General Motors Research and Development Center Warren USA3Tongji University Shanghai ChinaShow Abstract
High capacity solid-state storage of hydrogen suitable for transportation applications remains elusive despite more than a decade of intense renewed interest. However, efforts towards hydrogen/oxygen fuel cell vehicles have continued to progress using designs based on high-pressure (~350 to 700 bar) compressed hydrogen tanks. To augment the capacity of compressed tanks and achieve a solid-state storage material that is readily integrated with developing vehicle designs, we have focused on room temperature high-pressure molecular hydrogen storage materials. Here we present results for storage in zeolite-templated carbon (ZTC) at pressures up to 200 bar. We will describe the synthesis and characterization of ZTC based on Zeolite Y and compare its hydrogen storage properties with conventional activated carbon materials, such as MSC-30. High fidelity templating yields ZTCs with high surface area (>3500 m2/g), high micropore volume (>1.5 cm3/g), and a well-ordered pore structure (sharp diffraction feature at 6 degrees two theta). In addition, room temperature high-pressure storage capacities can exceed those for MSC-30 (~1.2 wt% compared to 1.0 wt% at 215 bar). Importantly, the isotherms for our best ZTC materials are straighter than those for MSC-30, potentially indicating much greater saturation capacities at higher pressures. This difference from MSC-30 and other activated carbons may be a manifestation of the unique ordered pore structure for ZTC materials.
10:45 AM - P1.5
The Role of Native Defects in the Decomposition of Complex Hydrides
Khang Hoang 1 2 Anderson Janotti 1 Chris G Van de Walle 1
1University of California Santa Barbara USA2Naval Research Laboratory Washington USAShow Abstract
Complex hydrides such as alkali amides, borohydrides, and alanates have been considered as potential materials for hydrogen storage due to their high hydrogen content. Yet these materials usually exhibit poor thermodynamics, kinetics, and/or reversibility. For the purpose of optimizing their hydrogen storage and release capacity, it is essential to understand the fundamental mechanisms behind the decomposition and dehydrogenation of the materials, identifying the rate-limiting processes involved in the hydrogen desorption. First-principles calculations based on density-functional theory is a powerful tool for addressing the issues. In this talk, we present results for the structure, energetics, and migration of native point defects and defect complexes in LiNH2, and propose specific mechanisms for its decomposition, providing an explanation for the effects of ball milling and the dehydrogenation of (LiNH2+LiH) mixtures. We also discuss the relationship between the structure of hydrogen-related defects and the end products in the decomposition reaction, which can be extended to the various complex hydrides.
11:30 AM - *P1.6
Theoretical Prediction of Hydrogen Storage Materials: Crystal Structures and Reaction Pathways
Yongsheng Zhang 1 Christopher Wolverton 1
1Northwestern University Evanston USAShow Abstract
Metal borohydrides [M(BH4)n] are receiving a lot of attention in hydrogen storage research due to their high gravimetric capacities of hydrogen. In particular, the most widely-studied compounds in this class, Mg(BH4)2 (14.9 wt.%), and Ca(BH4)2 (11.6 wt.%), exhibit theoretical hydrogen contents above the DOE system-level target for passenger vehicles. Unfortunately, the temperatures for hydrogen release are too high and hydrogen cannot be extracted using the waste heat from proton exchange membrane (PEM) fuel cells (operating at approximately 80 C). Therefore, recent research has concentrated on clarifying the physical and chemical factors that determine the decomposition temperatures of borohydrides. Density-functional theory (DFT) has been used to accurately study a wide range of thermodynamic and kinetic properties of many H2 storage materials. The DFT+Monte-Carlo based method to predict low energy crystal structures, the prototype electrostatic ground state (PEGS) method, has successfully predicted crystal structures of complex hydrides with anion groups like [BH4]- and [B12H12]2-. Here we present an overview of our recent PEGS+DFT work on crystal structures, hydrogen decomposition pathways, and decomposition intermediates of metal borohydrides: Ca(BH4)2, Mg(BH4)2 and AlB4H11.
12:00 PM - P1.7
Research Status of Adsorbent Materials for On-board Hydrogen Storage Applications
Anne Dailly 1 Eric Poirier 2 Tyler Voskuilen 3
1General Motors Warren USA2Optimal Inc. Plymouth Township USA3Purdue University West Lafayette USAShow Abstract
Realizing the widespread commercialization of hydrogen-fueled vehicles still requires overcoming technical barriers such as the development of an on-board hydrogen storage system. The research community has been actively trying to develop advanced hydrogen solid-state storage alternatives to compressed gas which is the present benchmark technology. In this study we report the research conducted at General Motors Global R&D Center on adsorption based systems. An extended set of microporous adsorbents has been under evaluation for on-board application either at low pressures/cryogenic conditions or high pressures/ambient temperature. The materials hydrogen storage properties (gravimetric and volumetric uptakes, kinetics and thermodynamics) were assessed through measurements and analysis. The objective was to understand the sorption storage mechanism and its relationship to key materials properties for the specific (P, T) operating conditions. Useful insights about performance and limitations of such materials as well as potential optimization paths to reach the on-board hydrogen storage targets will be presented.
12:15 PM - P1.8
Reticular Materials for Hydrogen Storage
Stefano Leoni 1 Igor Baburin 1 Gotthard Seifert 1
1Dresden University of Technology Dresden GermanyShow Abstract
Hydrogen is an appealing energy carrier for clean energy use. However, hydrogen storage is still one of the main bottleneck for an energy economy based on hydrogen. Many materials have been synthesized to store a sufficient amount of hydrogen for practical use. However, no material yet meets the US DOE recommendations for reversible hydrogen storage under near ambient conditions. We have started a systematic investigation of promising hydrogen storage candidate materials to meet this challenge. We consider â?otraditionalâ?o carbon materials on the one hand, on the other we focus on open framework zeolitic materials like MOFs, COFs and recently ZIFs. MOFs and ZIFs [1,2] are mechanically versatile and easy to synthesise. On combining topological enumeration, molecular dynamics and structure optimization we are poropsing a catalogue with useful hydrogen uptakes. Upon chemical subtitutions we are able to enhance the specificity for hydrogen, for instance by introducing polarizing centers in the framework. On the carbon front , we propose matrices of carbon nanotubes with different orientations and entanglements as a highly promising medium surpassing all carbon materials proposed so far, with its 5.5% H2 adsorption at 300 K. The talk will have a review character and will span over different material classes and computational methodologies.  I. A. Baburin, B. Assfour, G. Seifert and S. Leoni, Dalton Trans. DOI: 10.1039/C0DT01441A.  B. Assfour, S. Leoni and G. Seifert, JPC C DOI: 10.1021/jp101958p.  B. Assfour, S. Leoni, G. Seifert, I. A. Baburin, Adv. Mat. DOI: 10.1002/adma.201003669
12:30 PM - P1.9
Reversibility Aspect of Lithium Borohydrides
Ming Au 1 Yaping Sun 2 Frederick E Pinkerton 3
1Savannah River National Laboratory Aiken USA2Clemson University Clemson USA3General Motors Warren USAShow Abstract
Reversibility is the key for any hydrogen storage material to be developed. Borohydrides such as LiBH4 have been studied or proposed as candidates for hydrogen storage because of their high hydrogen contents (18.4 wt% for LiBH4). Limited success has been made in reducing the dehydrogenation temperature. However, full rehydrogenation has not been realized. It is found that the dehydrogenation mechanism of metal borohydrides differs signicantly from the well-known metal hydrides such as LaNi5H6 and MgH2 that release hydrogen in a single chemical decomposion step. Some of the steps in the multiple step decomposition processes of metal borohydrides are not reversible. Furthermore, the decomposition also produces stable intermediate compounds that can not be rehydrided easily. Although our experiments show the partial reversibility of the doped LiBH4, it was not sustainable during dehydriding-rehydriding cycles because of the accumulation of hydrogen inert species. Doping with additives reduces the stability of LiBH4, but it also makes LiBH4 less reversible. It raises reasonable doubt on the feasibility of making metal borohydrides suitable for reversible hydrogen storage. We will present our experimental data on doped LiBH4 and bimetallic borohydride synthesized in our labs.
Symposium OrganizersEric Majzoub, University of Missouri, St. Louis
Jason Graetz, Brookhaven National Laboratory
Vidvuds Ozolins, University of California, Los Angeles School of Engineering and Applied Sciences
Petra de Jongh, Utrecht University
P4: Carbon Capture Materials Theory
Wednesday PM, April 11, 2012
Moscone West, Level 2, Room 2022
2:30 AM - *P4.1
Computational Carbon Capture
Berend Smit 1
1UC Berkeley Berend Smit USAShow Abstract
Reducing anthropogenic global CO2 emissions is a complex issue. The scale of the problem, the costs, its interdependence with energy production, and the intrinsic uncertainties in making long- term predictions about something as complex as the climate are a few of the factors contributing to one of the biggest challenges of our time. Despite advances in alternative energy, most, if not all, future energy scenarios include continuing growth in the absolute use of fossil energy. Carbon dioxide capture and storage (CCS) deployed at an industrial scale, is one of the few viable technologies that mitigate anthropogenic CO2 emissions. For power plants, post combustion CCS involves the separation of CO2 from flue gas, followed by its compression and then sequestration in geological formations. CCS is very energy intensive, and capture dominate both the energy consumption and the cost. One of the main bottlenecks to deploying large-scale CCS in power plants is the energy required to separate the CO2 from flue gas. For example, near-term CCS technology applied to coal-fired power plants is projected to reduce the net output of the plant by some 30% and to increase the cost of electricity by 60-80%. Developing capture materials and processes that reduce the parasitic energy imposed by CCS is therefore an important area of research. We have developed a computational approach to rank adsorbents for their performance in CCS. Using this analysis, we have screened hundreds of thousands of zeolite and ZIF structures and identified many different structures that have the potential to reduce the parasitic energy of CCS by 30-40% compared to near-term technologies.
3:00 AM - P4.2
Solid Sorbent Modeling in the Department of Energyrsquo;s Carbon Capture Simulation Initiative
David S Mebane 1 K. Sham Bhat 2 Leslie M Moore 2 Andrew Lee 1 Joanne Wendelberger 2 David C Miller 1
1National Energy Technology Laboratory Morgantown USA2Los Alamos National Laboratory Los Alamos USAShow Abstract
The Carbon Capture Simulation Initiative is a Department of Energy-wide project aimed at reducing the development time for carbon capture technology through advanced simulation. The goal of the project is to link scientifically sophisticated models at the scale of chemical reactions through to the scale of plant operations with the aid of rigorous statistical analysis. As a demonstration of the simulation methodology, the project is focusing on solid sorbent technology. The particular sorbent of interest is a mesoporous silica supported amine. Thermodynamic, kinetic and microstructural models at various levels of detail have been produced for this sorbent; the presentation will contain an overview of ongoing modeling efforts, including a discussion of insights gained from comparison of models with experimental data, and the role of uncertainty quantification in model integration.
3:15 AM - P4.3
Gas Diffusion in Zeolitic Imidazolate Frameworks with the rho; Topology from Molecular Dynamics
David L. Olmsted 1 Keith Ray 1 2 Jessica Burton 1 Yao Houndonougbo 3 Ning He 4 Brian Laird 4 Mark Asta 1
1University of California, Berkeley Berkeley USA2University of California, Berkeley Berkeley USA3Eastern Washington University Cheney USA4University of Kansas Lawrence USAShow Abstract
Zeolitic imidazolate frameworks (ZIFs) are promising materials for carbon capture and other CO_2 separation applications because of superior chemical and thermal stability, and reasonable adsorption and selectivity. In these processes, the kinetics of adsorption and selectivity is as important as the equilibrium adsorption and selectivity. We report on classical MD simulations studying the effect of different functionalizations of the imidazole linkers on the diffusion of CO_2 and other gases in ZIFs with identical zeolite-Ï topologies. The chemical differences in the functional groups can have a large impact on transport rates. For example, the tracer diffusion constant for CO_2 varies by a factor of 20 over the ZIFs studied. This research is supported by the Energy Frontier Research Center: Molecularly Engineered Energy Materials, funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001342.
4:00 AM - *P4.4
Topology Dependence of CO2 Adsorption and Selectivity in Zeolitic Imidazolate Frameworks: A Combined Experimental and Computational Study
Brian B Laird 1 Ning He 1 Keith Ray 2 William Morris 3 Hiroyasu Furukawa 3 Peter Klonowski 3 Omar M Yaghi 3 Mark Asta 2
1University of Kansas Lawrence USA2University of California-Berkeley Berkeley USA3University of California-Los Angeles Los Angeles USAShow Abstract
Zeolitic Imidizolate Frameworks (ZIFs) are nanoporous materials that have considerable potential in carbon capture and separation applications due to high CO2 adsorbance and selectivity. In previous work [J. Amer. Chem. Soc. 132, 1008 (2010)], we examined the role of functionality on CO2 uptake using a series of ZIFs with identical topology, but varying functionalization. In this current work, we use direct experimental measurements and computer simulation to study the effect of topology by examining the adsoption and selectivity of CO2, N2 and CH4 in ZIFs with fixed imidazolate functionalization but varying topology.
4:30 AM - P4.5
Estimating the Efficacy of Metal-organic Frameworks for Swing-sorption Carbon Capture
Jason Simmons 1 Hui Wu 1 2 Wei Zhou 1 2 Taner Yildirim 1 3
1NIST Gaithersburg USA2University of Maryland College Park USA3University of Pennsylvania Philadelphia USAShow Abstract
With the current prevalence of hydrocarbon-based energy sources, carbon capture and sequestration are essential technologies for minimizing the emission of carbon dioxide and the resulting increased atmospheric concentration of CO2. Current technologies based on absorption require high temperature regeneration of the solvent, ultimately leading to significantly decreased efficiency and increased cost. Development of an adsorption-based technology, based on physical adsorption in optimized porous media, would greatly reduce the regeneration costs. Here we discuss the carbon capture performance of a range of metal-organic frameworks (MOFs), with particular focus on their applicability to swing-sorption techniques. In particular, we demonstrate that MOFs can capture significant amounts of CO2 and that the CO2 can be readily removed from the MOF using standard pressure/vacuum swing techniques. The role of flue gas impurities on the capture capacity is also discussed.
4:45 AM - P4.6
First Principles Studies of CO2/CH4 Binding and Selectivity in Zeolitic Imidazolate Frameworks
Keith Ray 1 David Olmsted 2 Ning He 3 Yao Houndonougbo 4 Brian Laird 3 Mark Asta 2
1UC Berkeley Berkeley USA2UC Berkeley Berkeley USA3University of Kansas Lawrence USA4Eastern Washington University Cheney USAShow Abstract
Zeolitic Imidazolate Frameworks (ZIFs) possess high surface area, selectivity, and stability which make them excellent candidates as carbon capture and natural gas separation materials. Due to the complexity and variety of these structures, a fundamental understanding of the interactions between gas and framework molecules that govern CO2 and CH4 uptake is useful to guide the design of materials with optimal capture and selectivity related properties. To do this we performed a detailed first principles computational analysis of multiple binding sites on a set of ZIFs with different chemical functionalizations. We found a variety of binding behaviors depending on the functional groups near to the binding site and this effect varied in different sites and with different gas species. Since a large contribution of the attraction comes from van der Waals (vdW) forces, we report binding energies obtained from different flavors of the vdW-DF [2,3,4], a still evolving density functional theory (DFT) method which includes a non-local correlation energy. Binding sites are identified with inexpensive classical simulations and comparisons are made between calculations and experimentally measured values of the heat of adsorption and adsorption isotherms . This research is supported by the Energy Frontier Research Center â?oMolecularly Engineered Energy Materials,â? funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001342.  W. Morris, B. Leung, H. Furukawa, O. K. Yaghi, N. He, H. Hayashi, Y. Houndonougbo, M. Asta, B. B. Laird, O. M. Yaghi, J. AM. CHEM. SOC. 2010, 132, 11006-11008  M. Dion, H. Rydberg, E. Schroder, D. C. Langreth, B. I. Lundqvist, Phys. Rev. Let. 92, 246401 (2004)  K. Lee, E. D. Murray, L. Kong, B. I. Lundqvist, and D. C. Langreth, Phys. Rev. B 82, 081101 (2010).  J. Klimes, D. R. Bowler, and A. Michaelides, J. Phys. Condens. Matter 22, 022201 (2010).
5:00 AM - P4.7
Understanding the Preferential Adsorption and Separation of CO2 over N2 in a Flexible Metal Organic Framework
Nour Nijem 1 Peter Thissen 1 Yanpeng Yao 2 Roberto Longo 1 Katy Roodenko 1 Haohan Wu 3 Yongang Zhao 3 Kyeongjae Cho 1 Jing Li 3 David Langreth 2 Yves Chabal 1
1University of Texas at Dallas Richardson USA2Rutgers University Piscataway USA3Rutgers University Piscataway USAShow Abstract
The unusual stepped uptake behavior in isotherms and the high selective adsorption of CO2 over N2 and methane observed in a flexible framework, Zn2(bpdc)2(bpee) where bpdc= 4,4â?T-biphenyl dicarboxylate, bpee=1,2-bis(4-pyridyl)ethylene are examined using Raman scattering, infrared (IR) absorption spectroscopy and van der Waals-Density Functional Theory (vdW-DFT) calculations. Clear evidence for structural changes in the framework occurring as a result of CO2 adsorption is observed. The high quadrupole moment of CO2 and its specific interaction through its oxygen induces a twisting of the two benzene rings in the bpdc linker. This twisting induces a small rotation of the C-O bond around the metal center. This phenomena is derived from a red shift in the C-C stretch mode, a decrease in Raman intensity of the C=O bond and a blue shift in the unidentate C-O bond stretch mode of the bpdc linker. As a response to the twisting of the bpdc linker, a blue shift of the C=C bond absorption band of the bpee linker is also observed. These observations indicate changes in the frameworkâ?Ts structure that opens the initially distorted parallelogram into a more rectangular structure, thereby allowing more CO2 to be adsorbed. IR absorption spectroscopy measurements performed at lower pressures indicate that the CO2 interaction with the C-C inter-ring bond is through the CO2 oxygen. vdW-DFT calculations show that there are 16 CO2/unit cell at full loading, with more energetically favorable adsorption positions for the CO2 molecules closer to C-C bond of the bpdc linker and the C=C bond of the bpee linker instead of the benzene and pyridine rings of these linkers. At higher loading, the initial positions of the CO2 molecules change due to CO2-CO2 interactions, causing a slightly weakening of the CO2 interaction with the bpee linker. This theoretical prediction is observed experimentally through a red shift in the C=C bond stretch mode as more CO2 is adsorbed. In summary, this work points to the main structural transformations resulting from the frameworkâ?Ts flexibility and identifies the connectivity of the bpdc linker to the metal at one end in a monodentate configuration and the flexibility of the bpee pillars themselves as the reasons for the frameworkâ?Ts flexibility. The unique CO2 interaction with the C-C inter-ring of the bpdc linker and the resulting twisting of the bpdc linker (gate opening mechanism) accounts for the high selectivity towards CO2.
5:15 AM - P4.8
Ionic Liquid/Metal-Organic Framework Composite for CO2 Capture: A Computational Investigation
Yifei Chen 1 Zhongqiao Hu 1 Krishna M Gupta 1 Jianwen Jiang 1
1National University of Singapore Singapore SingaporeShow Abstract
As a unique class of green solvents, ionic liquids (ILs) are nonvolatile and nonflammable with high thermal stability, and thus might potentially substitute traditional solvents. Since the first observation of high CO2 dissolution in ILs, a large number of experimental and theoretical studies have been devoted to the potential use of ILs for CO2 capture. However, there are two major issues in the use of ILs for CO2 capture, i.e., the cost and high viscosity of ILs. As a new strategy, supported ILs (SILs) have been recently proposed in which ILs impregnate the pores of a solid porous support. Most studies to date have used either organic polymers or inorganic zeolites as supports to prepare SILs. In the last decade, a new family of porous materials, namely metal-organic frameworks (MOFs) have emerged. The vast choice of organic linkers and metal oxides allow unlimited number of MOF structures to be tuned in a rational way. Consequently, MOFs possess a wide range of surface areas (up to 6500 m2/g) and pore sizes (up to 4.5 nm), thus could act as versatile porous supports for SILs. Although numerous experimental and simulation studies have been reported separately for ILs and MOFs, we are not aware of any study for MOF-supported ILs. In this study, for the first time, we propose a MOF-supported IL (or IL/MOF composite) and demonstrate its application for post-combustion CO2 capture by a computational approach. The composite selectively adsorbs CO2 from CO2/N2 mixture, and the selectivity increases with increasing IL ratio in the composite. At a weight ratio IL/MOF = 1.5, the selectivity is about 70 at ambient conditions (300 K and 1 bar), which is higher than that in pure MOF, pure IL, and many other supported ILs.
5:30 AM - P4.9
First-principles Studies of the Atomic, Electronic, and Magnetic Structure of alpha;-MnO2 (Cryptomelane)
Eric Cockayne 1 Lan Li 1
1NIST Gaithersburg USAShow Abstract
Tunnel-containing manganese dioxide (MnO2)-based materials are of great interest for carbon storage applications. First-principles density functional theory calculations are used to investigate Î±-MnO2, a structure containing a framework of corner and edge sharing MnO6 octahedra with tunnels in between. Calculations show that placing additional species, such as K+ ions, into the tunnels can stabilize Î±-MnO2 with respect to the rutile-structure Î²-MnO2 phase, in agreement with experiment. The determined magnetic structure has antiferromagnetic Mn-Mn interactions between corner-sharing octahedra and ferromagnetic Mn-Mn interactions between edge-sharing octahedra, but long-range magnetic order is only expected at cryogenic temperatures. Pure Î±-MnO2 is found to be a semiconductor with an indirect band gap of 1.3 eV. The main effect of placing ions such as K+ inside the tunnel is to shift the Fermi level. Water and related hydrides (OH-; H3O+) can also be accommodated in the tunnels. When both K+ and an oxygen hydride are present in the tunnel, the K-O distance increases with increasing oxygen hydride charge, as expected from electrostatics.
5:45 AM - P4.10
Innovative Materials for Carbon Capture in Green Solvents
Sarah Baker 1 Carlos Valdez 1 Lucas Koziol 1 Tripp Floyd 1 Josh Stolaroff 1 William Bourcier 1 Felice Lightstone 1 Joe Satcher 1 Roger Aines 1
1Lawrence Livermore National Laboratory Livermore USAShow Abstract
Amine-based aqueous liquids used for carbon dioxide capture remain the benchmark for large-scale management of carbon dioxide emissions, but suffer from a variety of problems including high cost, energy demand, and potential environmental impacts. These problems might be mitigated by using aqueous buffer salts such as potassium bicarbonate/potassium carbonate as the carbon dioxide sorption solvents. However, while non-amine based buffer systems have high capacities, they tend to suffer from poor kinetics of carbon dioxide hydration. In order to compete with the amine based solvents their hydration rates need to be improved. Small molecule mimics of the carbonic anhydrase active site facilitate enhanced CO2 hydration at near neutral pH, with a concomitant reduction in the energy penalty for solvent regeneration, therefore have the potential to dramatically improve the post-combustion capture of carbon dioxide in environmentally benign solvents. We have used computational design to develop catalysts that mimic the active site of carbonic anhydrase with the goal of surpassing the kinetics of the amine-based solvents and have shown that our computational models are predictive. In order to use the resulting optimized catalysts and solvents more effectively, we have developed new materials which will improve carbon dioxide mass transfer from the gas to the liquid phase. These new materials include catalytic surfactants that increase carbon dioxide hydration rates at the air/water interface while reducing the amount of catalyst needed in the overall process. We will describe the synthesis, catalytic rates, and surfactant properties of this new class of functional surfactant. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
P3: Hydrogen Storage in Metal-organic Frameworks and Porous Carbons
Wednesday AM, April 11, 2012
Moscone West, Level 2, Room 2022
9:00 AM - *P3.1
Nanoconfinement Effects in Energy Storage Materials
Maximilian Fichtner 1
1Karlsruhe Institute of Technology Karlsruhe GermanyShow Abstract
Nanoconfinement of energy storage materials such as metal hydrides and battery materials has been studied in a number of cases to modify physical and chemical properties of these materials.1 Hydrogen storage materials exhibit faster kinetics when they are infiltrated in mesoporous scaffolds. However, thermodynamic effects can only be observed if the particle size is below a critical value of 1.5-2 nm which has been shown by several theoretical studies. Particles with sizes lower than this value may change their thermodynamic properties leading to increased or decreased equilibrium pressures. Examples will be shown of NaAlH4 and MgH2 which was nanoconfined in microporous carbon hosts.2,3. The surprising effects with nanoconfined NaAlH4 (kinetic destabilization but thermodynamic stabilization) seems to have structural origins and can be explained by both theoretical calculations and recent measurements with inelastic neutron spectroscopy. Although strong kinetic effects have been observed, nanoconfinement of so far irreversible systems such as Mg(BH4)2 did not improve the reversibility even though a template directed approach was tried. The concept has also been applied in other energy storage materials and the properties of nanocompositic electrode materials will be discussed with several examples of insertion materials and conversion materials. In most cases, the cyclic stability and rate capability could be improved in these cases which points at kinetic effects and a stabilization of the particular microstructure of the system. Due to the direct coupling of the free energy with the electro motoric force a modification of the latter can be expected in the order of several 100 mV.4 Ref.:  M. Fichtner, Conversion materials for hydrogen storage and electrochemical applications - concepts and similarities, J. Alloys Compd. 509S (2011) S529 â?" S534  W. Lohstroh, A. Roth, H. Hahn, and M. Fichtner, Thermodynamic effects in nanoconfined NaAlH4, Chem. Phys. Chem. 11 (2010) 789-792  Zh. Zhao-Karger, JJ. Hu, A. Roth, D. Wang, Ch. KÃ¼bel, W. Lohstroh and M. Fichtner, Altered Thermodynamic and Kinetic Properties of MgH2 Infiltrated in Microporous Scaffold, Chem. Comm. 46 (2010) 8353-8355.  M. Fichtner, Nanoconfinement effects in energy storage materials, Phys. Chem. Chem. Phys. (2011) Perspective Article, DOI: 10.1039/c1cp22547b
P5: Poster Session
Wednesday PM, April 11, 2012
Marriott, Yerba Buena, Salons 8-9
9:00 AM - P5.1
Effect of Temperature on Mesoporous Carbon Nanofibers for Hydrogen Storage Behaviors
Ji-Eun Im 1 Jing Li 1 Yong-Rok Kim 1
1Yonsei University Seoul Republic of KoreaShow Abstract
Porous carbons are well known as one of the best adsorbents for gases. This property is due to the ability of this material to exhibit very different morphologies with highly porous structure and the existence of particular interactions between the carbon atoms and gas molecules. In this study, the fabricated mesoporous carbon nanofibers (MCNF) were tested for their capacities of hydrogen storage. The MCNF were synthesized by using a template of mesoporous silicate nanofibers within anodic aluminum oxide (AAO) film and furfuryl alcohol for the carbon source at the carbonization temperatures (600, 900, 1200 Â°C). Due to the easy controllability of pore size and thickness of AAO nanochannels, the diameter and length of MCNF could be custom synthesized for a specific application. The morphology differences of the MCNFs carbonized at 600, 900, and 1200 Â°C were studied based on the factors of the I(D)/I(G) ratio, the size of graphene layer (La), the BET surface area, and the pore volume. The hydrogen uptake capacity which sensitively depended on the above factors was measured at 77 K and ambient pressure of 0.1 MPa. The MCNF-1200 with the largest BET area and pore volume provided the highest hydrogen strorage of 0.74 wt.% among the MCNFs investigated in this study. Such higher hydrogen adsorption with the MCNFs carbonized at high temperature is expected to be from the larger surface area which is caused by bigger volume contraction and the change of the structure. This study successfully demonstrates the improved hydrogen uptake efficiency of MCNF induced by the carbonization temperature for the first time. Furthermore, the characteristics of the MCNF can be temperature tuned for a specific application purpose.
9:00 AM - P5.10
Hydrogen Storage in Carbon Cones
Jiri Muller 1 Hennig Heiberg-Andersen 1 Theodore Steriotis 2 A. Gotzias 2
1Institute for Energy Technology Kjeller Norway2NCRS "Demokritos" Aghia Paraskevi Attikis GreeceShow Abstract
Large scale production of conical carbon nanostructures (so-called carbon cones)  that are fundamentally different from the other nanocarbon materials, such as buckyballs and nanotubes, can be made using the so-called Kvaerner Carbon Black & Hydrogen Process . This involves pyrolysis of hydrocarbons using a torch plasma process. The carbon cones that occur appear in five distinctly different forms. Earlier reports indicated that these structures exhibit unusually high H2 uptake and release at room temperature not known in other forms of carbon . Here we report about the recent progress of the experimental research and theoretical modelling of these cluster particles with emphasis on H2 storage. References:  Helgesen et al, Mater.Res.Soc.Symp.Proc. Vol. 1057, 2008 Materials Research Society.  Kvaerner ASA, patent No. PCT/NO98/00093 for production and micro domain particles by use of plasma process.  Norwegian patent No. 307986 (2000), US patent no.6,290, 753 (2001), EPO Patent No. 1051539 (2004), Hydrogen storage in carbon materials
9:00 AM - P5.11
Novel Synthetic Approaches towards Microporous Polymer Networks
Christian Widling 1 Eduard Preis 1 Ullrich Scherf 1 Satish Patil 2 Gunther Brunklaus 3 Johannes Schmidt 4 Arne Thomas 4
1Bergische Universitaet Wuppertal Wuppertal Germany2Indian Institute of Science Bangalore India3Max Plank Institut fuuml;r Polymerforschung Mainz Germany4Technische Universitaet Berlin Berlin GermanyShow Abstract
Microporous polymer networks (MPNs) with their rigid, crosslinked architecture can show high SBET surface areas. The resulting high gas storage capacities make such MPNs promising candidates for an use as gas storage materials. One important synthetic challenge is the synthesis of such MPNs under mild reaction conditions including moderate processing temperatures, inexpensive catalysts and a preferably metal-free regime. The BET isotherms of a series of novel MPNs generated in an acid catalyzed Friedel-Craft-type self-condensation of A2B2- and A2B4- type fluorenone monomers have been recorded. The monomers form a cross-linked network in a single reaction step. The observed high intrinsic porosity indicates an open network structure. The condensation products show SBET areas of up to 1400 m2 g-1. An additional increase of the SBET value to up to 1800 m2 g-1 could be achieved by treating the MPNs with supercritical CO2.  E. Preis, C. Widling, U. Scherf, S. Patil, G. Brunklaus, J. Schmidt, A. Thomas, Polym. Chem. 2011, 2, 2186.
9:00 AM - P5.12
Stability and Hydroxylation of Isotypical MOFs Based on Paddle-wheel SBUs Containing Different Transition Metal Ions
Kui Tan 1 Nour Nijem 1 Qihan Gong 2 Jing Li 2 Yves J Chabal 1
1The University of Texas at Dallas Richardson USA2Rutgers University Piscataway USAShow Abstract
Instability of most prototypical metal organic frameworks (MOFs) in the presence of moisture is always a limitation to commercial scale development. In this work, we combine in situ IR adsorption spectroscopy, ex situ Raman spectroscopy and Powder X-ray Diffraction to monitor the structural decomposition of paddle wheel metal cluster building units in a well-known class of metal organic frameworks M(bdc)(ted)0.5 [H2bdc = 1,4-benzenedicarboxylic acid; ted = triethylenediamine; M=Cu, Ni, Zn, Co] as a function of humidity and temperature. For Cu(bdc)(ted)0.5, the stability of this pillared framework in water vapor is found to related with water vapor condensation inside the pores. A hydrolysis reaction of water molecules with Cu-O-C group is observed by in-situ IR spectroscopy at pressures sufficient to induce condensation, namely the appearance of M-OH modes and the loss of M-O- bonds. In these conditions, water dissociates at the metal oxide sites, i.e. interaction among water molecules upon condensation weakens the H-O-H bond and therefore lower the barrier for the dissociation reaction of water molecules with metal-oxygen bonds. A series of tests have been performed to determine the reversibility and regeneration of the frameworks. Other M(bdc)(ted)0.5 series(M=Zn, Ni, Co) have been measured in humid environments to obtain an in-depth understanding of the effects of different central metal ions on the stability of the structure. The initial decomposition pathway of paddle wheel building units and the overall stability in vapor are examined in the context of intrinsic parameters in these isotypical M[dicarboxylate][diamine]0.5 compounds (Bond strength or bond dissociation energy of metal oxygen or metal nitrogen, Inertness of central metal ions, Irvine-William series for transition metals). The findings of this work provide information that is necessary for determining operating conditions of this class of MOFs with a paddle wheel secondary building unit in harsh environments and to guide developments of more robust units.
9:00 AM - P5.13
Irreversible High-temperature Hydrogen Interaction with the Metal Organic Framework Cu3(BTC)2
Anna Grzech 1 Jie Yang 2 Theo J Dingemans 2 Subramanian Srinivasan 3 Pieter C.M.M. Magusin 3 Fokko M Mulder 1
1Delft University of Technology Delft Netherlands2Delft University of Technology Delft Netherlands3Eindhoven University of Technology Eindhoven NetherlandsShow Abstract
Hydrogen absorption in metal organic frameworks with partly exposed metal ions has attracted significant interest in view of the potentially larger interaction strength of the metal with the adsorbed hydrogen molecule, resulting in higher operating temperatures. Likewise, highly porous structures are of interest as a template for nanosizing light metal hydrides, altering their sorption properties. Here we report that in the metal organic framework Cu3(BTC)2, containing open Cu2+ sites, at temperatures between 323 â?" 423 K and 2 bar H2 pressure, H2 dissociates and chemically binds with a total irreversible hydrogen uptake of 1.1 wt.%. FT-IR and NMR experiments confirm that the BTC linkers are converted into the carboxylic acid starting material, while XRD reveals the presence of Cu0 metal particles and decomposition of the framework. The exposed Cu2+ sites thus show strong enough chemical reactivity to split H2. When designing MOFs for storage applications and as template for light metal hydrides one has to take into account the potentially destructive reactivity of the metal centers.
9:00 AM - P5.14
Size-scaling Behavior of Hydriding Phase Transformations in Nanocrystals
Rizia Bardhan 1 Lester O Hedges 1 Cary L Pint 2 Ali Javey 2 Stephen Whitelam 1 Jeffrey Urban 1
1Lawrence Berkeley National Lab Berkeley USA2University of California, Berkeley Berkeley USAShow Abstract
Understanding the energetics of hydrogen induced phase transformations at solid-gas interfaces is of particular importance as it provides a route to tune the thermodynamic and kinetic limitations of metal hydrides. Nanocrystal size-effects play a key role in controlling the thermodynamics and kinetics of nucleation events associated with phase transformations. Currently, experimental understanding of how nanoparticle size controls the rates and energies of metal-hydride formation and decomposition is limited, due to challenges both in directly probing these events at the nanoscale and preparing uniform samples over a series of sizes. Here, by monitoring the luminescence of metal nanocrystals in-situ, we determine for the first time the thermodynamics and kinetics of hydride nucleation and decomposition within a size-series of monodisperse palladium (Pd) nanocrystals. The unique combination of a rapid and sensitive optical technique applied to size- and shape-controlled nanocrystals reveals clearly how nanocrystal surfaces impact thermodynamic and kinetic barriers to hydride nucleation, unencumbered by substrate or antenna-coupling effects. Furthermore, by partnering our experimental data with a statistical mechanical model, it strongly suggests that hydride nucleation in palladium nanocrystals is driven by thermal fluctuations, enabling prediction of hydride nucleation barriers as a function of temperature and nanocrystal size. Such understanding is critically important for the rational design of nanocrystals not only for hydrogen storage, but also for gas sequestration, gas sensing, and catalysis.
9:00 AM - P5.16
Thermodynamic Tuning of Calcium Hydride by Fluorine Substitution
Eugenio Riccardo Pinatel 1 Line H Rude 2 Marta Corno 1 Piero Ugliengo 1 Torben R Jensen 2 Marcello Baricco 1
1University of Torino Torino Italy2Aarhus University Aarhus DenmarkShow Abstract
Anion substitution is a possible strategy to tune the thermodynamic properties of hydrides with high gravimetric density . Hydrogen can be partially substituted by anions with different size and electronegativity, changing the H-bonding strength and thereby modifying the thermodynamics of hydrogen sorption. If the forming solid solution has a positive enthalpy of mixing, a decrease of the enthalpy of dehydrogenation for the pure hydride is expected. As a consequence, the decomposition temperature of very stable hydrides can be reduced. On the contrary, if a negative enthalpy of mixing is observed, the enhanced enthalpy of dehydrogenation of the solid solution might increase the decomposition temperature of hydrides with low stability. Fluorine is a good candidate for H-substitution in hydrides, because of a size similar to H, high electronegativity and low weight. So, even for a minor degree of substitutions, relevant changes in the thermodynamics of hydrogen sorption are expected, without significant reduction of gravimetric density. Anion substitutions in CaH2 have been observed during hydrogen sorption reactions of Ca(BH4)2 destabilized with fluorine additions . The formation of a Ca(H,F)2 solution with the cubic structure of the fluoride was experimentally evidenced . A recent theoretical study  suggests a relevant solubility of F in the orthorhombic structure of the hydride. So, in the present work, fluorine substitution in calcium hydride has been investigated, combining experimental and theoretical studies. CaH2-CaF2 mixtures with various molar ratios have been prepared by ball milling. Partial H-F substitution has been evidenced after ball milling. In situ X-ray Diffraction analysis has been carried out as a function of temperature by synchrotron radiation experiments. An increase of mixing has been observed during heating, with the formation of a single solid solution for 1:1 mixture. Ab-initio DFT calculations were performed to estimate the thermodynamic properties of solid solutions. Both orthorhombic and cubic solid solutions were modelled. In order to compare experimental data with calculations, a thermodynamic assessment within the CALPHAD framework has been performed and the pseudo binary CaH2-CaF2 phase diagram has been calculated. The formation of orthorhombic and cubic terminal solid solutions in the CaH2-CaF2 system is predicted, in good agreement with experimental findings.  H. W. Brinks, A. Fossdal, B. C. Hauback, J. Phys. Chem. C, 112 (2008) 5658  R. Gosalawit-Utke, K.Suarez, J. M. Bellosta Von Colbe, U. BÃ¶senberg, T. R. Jensen, Y. Cerenius, C. Bonatto Minella, C. Pistidda, G. Barkhordarian, M. Schulze, T. Klassen, R. Bormann, M. Dornheim, J. Phys. Chem. C 115 (2011) 3762  J. -F. Brice, A. Courtois, J. Aubry, J. Sol. St. Chem. 24 (1978) 381  J.Y. Lee, Y.-S. Lee, J.-Y. Suh, J.-H. Shim, Y. W. Cho, J. All. and Comp. 506 (2010) 721
9:00 AM - P5.17
TEM Guided Microstructural Design of Magnesium Hydride Alloys with Capability for Room Temperature Volumetric Absorption Cycling
David Mitlin 1 Peter Kalisvaart 1 Mohsen Danaie 1 Shu Tao 2 Ben Zahiri 1 Helmut Fritzsche 3
1University of Alberta and NINT NRC Edmonton Canada2Eindhoven University of Technology Eindhoven Netherlands3Chalk River Laboratories Chalk River CanadaShow Abstract
We will first discuss our recent alloy design efforts for both â?obulkâ? thin films and for thin film multilayer nanocomposites. The research culminates in the creation of several classes of catalysts that enable for relatively rapid room temperature volumetric absorption over multiple cycles at hydrogen pressures as low as 2 atmospheres. The same catalysts allow for ultra-rapid 250+ cycles elevated temperature absorption/desorption at hydrogen pressures between 1 and 3 atm. TEM analysis is utilized to elucidate the key microstructural features that allow for such exquisite kinetics. Second we will discuss our most recent cryogenic stage transmission electron microscopy (TEM) â?" based findings on the MgH2 to Mg (and vise versa) phase transformation. We show that both reactions proceed unevenly via sporadic nucleation, rather than by any â?ocontracting volumeâ? type of mechanism, and identify the dominant metal - hydride orientation relationships. Deformation twins in the hydride are discovered and are discussed in relation to the kinetics of hydrogen diffusion.
9:00 AM - P5.19
Acid/Base Activation of Carbon Nanotubes and Their Application for CO2 Capture
Xiaotian Zhang 1 Rajender Gupta 1 Weixing Chen 1
1University of Alberta Edmonton CanadaShow Abstract
High specific surface area (SSA) makes carbon nanotubes (CNTs) a potential nanomaterial for CO2 capture. Lately such chemical modification methods as element doping, polymer grafting and nitrogen groups impregnation have been investigated to further improve CO2 adsorbing performance of Carbon Nanotubes (CNTs). Chemical activation is also a promising approach. Herein a close look has been taken at the effect of both acid and base activations on multiwall CNTs by studying its adsorbing capacity of CO2. For base-activation, KOH is reported to be able to develop different sizes of pores on CNT structures. Effects of activation time and temperature are investigated in order to find out the optimized condition of activation. By analyzing the pore size distribution the relationship between pore size and adsorbing capacity can be determined. For acid-activation, various mixtures of sulfuric acid and nitric acid were used to introduce oxidized groups before nitrogen groups were grafted onto the surface of CNTs via chemical modification. TEM and XPS were employed to study the surface morphology and functional groups on the surface of CNTs. For both approaches, we use thermal gravimetric analysis to determine the CO2 adsorbing capacity. The results show that base-activated CNTs could improve the adsorbing capacity by more than 200%, while acid-activated CNTs can be further modified with amino groups and achieve equally/even better performance.
9:00 AM - P5.2
Measurement of Hydrogen Diffusivity through Amorphous Metallic Membranes
Wang Young-Im 1 Suh Jin-Yoo 1 Kim Ja Ryeong 1 Kim Yu Chan 1 Fleury Eric 1
1Korea Institute of Science and Technology Seoul Republic of KoreaShow Abstract
Metallic membranes can be utilized to separate hydrogen from a mixture of different gas molecules. By the solid state diffusion of atomic hydrogen through the interstitial sites of a metallic lattice, the solid membrane provides an efficient way to separate hydrogen with high hydrogen selectivity against other gases. Although palladium has been widely used for this application, recent interest in the hydrogen energy prompted the search for an alternative to the precious metal. Although Body-Centered Cubic (BCC) metals, such as V, Nb, and Ta, are most promising in terms of hydrogen flux, they are mechanically unstable when hydrogen is introduced and they lack catalytic ability for the dissociation and recombination of the hydrogen molecules. Another alternative group has been amorphous metal since the introduction of Ni64Zr36 reported in the year of 2000. Although it has been reported that some amorphous alloys with high zirconium content exhibit values for the hydrogen flux as high as that of palladium membranes, not much information are available regarding the diffusion characteristics and structural stabilities. This study evaluated the hydrogen flux and diffusivity through Ni-based metallic glass membranes composed by the elemental groups of Ni, Nb, and Zr as major constituents and of Fe, Co, and Ta as minor addition. The hydrogen diffusivity was measured by the Time-lag method which analyzes the initial transient behavior of the hydrogen diffusion until it reaches a steady state. The hydrogen diffusivity of the amorphous metallic membranes turned out to be about one order of magnitude smaller than that of palladium membrane. On the other hand, the amorphous membranes have higher hydrogen solubility to result in hydrogen flux comparable to that of palladium membrane. Furthermore, our data indicated that an increase in the zirconium content led to an increase in the hydrogen diffusivity as well as in the hydrogen solubility. However, the degradation of the hydrogen flux was found to occur more rapidly in amorphous membranes with high zirconium content. The mechanism of this degradation is discussed in terms of the hydrogen diffusivity and solubility.
9:00 AM - P5.21
One-pot Synthesis of Mesoporous Magnesia-Alumina Composite and Their Activity in the CO2 Adsorption
Jeong Gil Seo 1 Hyuk Jae Kwon 1 Soonchul Kwon 1 Hyun Chul Lee 1
1Samsung Advanced Institute of Technology Seoul Republic of KoreaShow Abstract
Adsorption process using the solid adsorbent has been known as the most promising technique for removal of CO2 from flue gases. Alkaline earth metal oxides, especially magnesium oxide and calcium oxide, have been utilized as the CO2 adsorbents. Magnesium oxide has advantage over calcium oxide due to its favorable CO2 adsorption-desorption kinetics at relatively low temperature (<400 oC). The surface to bulk ratio of magnesium oxide in the adsorbent is critical for the practical application because CO2 can only be adsorbed on the surface of magnesium oxide. Therefore, it is expected that adsorption performance of magnesium oxide can be maximized through the formation of magnesia-alumina composite structure with high mesoporosity. The objective of this work is to investigate the performance of mesoporous magnesia-alumina composite adsorbents in the CO2 adsorption, and to understand their adsorption mechanism. A series of mesoporous magnesia-alumina composites with different Mg/Al atomic ratio was prepared by a single-step sol-gel method. The prepared mesoporous magnesia-alumina composite adsorbents were denoted as XMgAl (X = 0.13, 0.25, 0.5, 1, and 3), where X represents the Mg/Al atomic ratio in the adsorbent. CO2 adsorption was carried out in a continuous flow fixed-bed reactor at atmospheric pressure. Each calcined adsorbent (25 mg) was charged into a tubular quartz reactor. CO2 concentration in N2 balance was fixed at 10 vol.%, and the total feed rate with respect to the adsorbent was maintained at