Simulations of Nanomaterials: Carbon Nanotubes, Graphene and Gold NanoclustersIvn Cabria, Mara J. Lpez, Luis M. Molina, Nicols A. Cordero, P. A. Marcos, A. Maanes and Julio A. AlonsoDpto. de Fsica Terica, Universidad de Valladolid, 47005 Valladolid, Spain

Group of Physics of Nanostructures

http://www.nanostructures.uva.es/indexenglidh.hyml

Universidad de ValladolidGroup of Physics of NanostructruresUniversity of ValladolidJ. A. AlonsoCabriaM. J. LpezL. M. MolinaUniversity of CantabriaA. MaanesUniversity of BurgosN. A. CorderoP. A. MarcosUAM Mexico: J. ArellanoUniv. Guanajuato Mexico: J. RoblesDIPC San Sebastian: A. RubioUniversity of Pennsylvania: L.A. Girifalco, K. Mahadevan, J. FischerInstituto del Carbn, CSIC, Oviedo:Nacho Paredes, Juan M. TascnArgonne National Laboratory: Stefan Vajda

Other collaboratorsGroup of Simulations of Materials

Main Lines of ResearchRelated with Nanomaterials and Nanotechnology

Can be focused on Materials and/or on Technological Applications

Simulations of Properties and Dynamics of Nanomaterials

Main Lines of Research Carbon Nanotubes

Hydrogen Storage for Hydrogen Cars

New Catalysts made of Gold Nanoclusters

The discovery of Carbon nanotubesAfter the C60 fullerene discovered in 1985CNTs are the new breakthrough of carbon, discovered in 1991Multiwall Carbon Nanotubes (MWCNTs) were produced by the arc discharge technique Nested cylinders of Carbon 4-30 nm in diameter 1 m in lengthIijima, Nature 354, 56 (1991)Ebbesen, Ajayan, Nature 358, 220 (1992)

Single Wall Carbon nanotubesBethune et al, Nature 363, 605 (1993)iron catalystcobalt catalystproduced by the arc discharge technique with a metal catalystIijima, Ichihashi, Nature 363, 603 (1993)

Geometrical Construction of SWCNTs Chiral vector: ChHamada et al, Phys Rev Lett 68, 1579 (1992)Saito et al, Appl Phys Lett 60, 2204 (1992)(n,m) uniquely specifies all posssible tube structures Translation vector: T Chiral angle: = angle ( a1 , Ch )by wrapping around a graphene strip in a seamless cylinder

Types of CNTs structures(5,5) Armchair, = 30Hamada et al, Phys Rev Lett 68, 1579 (1992)Saito et al, Appl Phys Lett 60, 2204 (1992)(9,0) Zigzag, = 0(10,5) Chiral, 0

Conducting character of SWCNTsHamada et al, Phys Rev Lett 68, 1579 (1992)Saito et al, Appl Phys Lett 60, 2204 (1992)n = m metallicn - m = 3q small gap semiconductorn m 3q moderate gap semiconductor

Carbon NanotubesMicroelectronics needs nanotubes of the same electronic characterSurfactants and nitronium molecular ions are used to attack selectively and separate the nanotubes in the bundlesSeparation of nanotubes by its metallic or semiconducting characterApplication of finite nanotubes to Spintronic: electrical current with spin polarization

Chemical sensors based on nanotubes very sensitive to different gasesFuncionalization of nanotubes with molecules and/or clustersChanges of the electrical conductivity of nanotubes due to extremely small amounts of gases adsorbed on the surface of the nanotubesApplications: environmental, medical, clean room control, etc.Carbon Nanotubes

Hydrogen Economy Production Hydrogen Storage Use: Fuel CellThree Aspects of an Economy based on Hydrogen- Hydrogen could be an alternative to conventional fossil-fuel sources of energy- Hydrogen is abundant and non contaminant- Hydrogen is NOT a primary source of energy but an energy vector

Hydrogen Economy Natural Gas: 50 % Production, most common Water electrolysis: for cheap electricity Biomass, pirolysis, photobiological processes (bacteria)ProductionElectrolysis of water

Hydrogen Economyhttp://www.nanostructures.uva.es/~cabria/hydrogeneconomyandothers.htmlProduction: Prices1 Kg hydrogen contains the same energy than 4.02 L of gasoline

1 Kg hydrogen occupies 1/0.000089 = 11200 L at normal conditions

1 Kg HydrogenNatural gas reforming 20035.0 USDUntaxed1 Kg HydrogenElectrolitic H,May 20063.3 USDUntaxed4.02 L GasolineSpain, July 20106.1 USDTaxed taxes=49 %4.02 L GasolineUSA, September 20102.9 USDTaxed taxes=18 %

Hydrogen Economy Onboard (cars) and in situ (buildings) storage Storage methods Liquid HydrogenCompressed HydrogenStored in a solidStorage

Hydrogen Car: Electric Car powered by a Hydrogen Fuel Cell instead of batteries Fuel Cell Electric Vehicle in CaliforniaHydrogen Fuel Cell Cars

Technological goal: Hydrogen cars equivalent to Fossil Fuel CarsBottlenecks: fuel cell efficiency and onboard storage

Onboard hydrogen storage targets for 2010:6 weight % of hydrogen0.045 Kg H2/Lat room temperature and moderate pressures, 40-100 atmsHydrogen Fuel Cell Cars

Types of Hydrogen Storage: gas, liquid and solid

Mechanisms of Solid Hydrogen Storage: physisorption, chemisorption and chemical reactions

Materials that store by physisorption: nanotubes, nanoporous carbons (CDCs, ACs, GNFs, etc.), porous materials such as MOFs, COFs, porous polymers, etc., and metal-doped carbonsHydrogen Fuel Cell Cars

Hydrogen Fuel Cell CarsCompressed hydrogen100-200 km of autonomy vs 500 km of gasoline carsAbout 2.5 times more expensive than gasoline carsHydrogen at 350 bars in Japan, at 700 bars in EuropeNo room for luggage: Tank with 110 H2 liters at 350 bars110 CV vs 200-300 CV of gasolineNorway, Fall 2006: First European public hydrogen stationElectric Cars powered by Hydrogen Fuel Cells instead of batteries

Hydrogen Onboard StorageOne of the main Hydrogen economy challengesHydrogen has a high energy density by mass: 120 MJ/kg (LHV) 140 MJ/kg (HHV) (gasoline: 44 MJ/kg)

But it has a low energy density by volume: 1.5 MJ/L at 150 bars, 0.01 MJ/L at 1 atm and 300 K, 8.4 MJ/L liquid H2 (gasoline: 35 MJ/L)Hydrogen Storage is one of the bottlenecks of present technology of Hydrogen Fuel Cell CarsLHV: Lower Heating Value; HHV: Higher Heating Value

Hydrogen Onboard StorageOne of the main Hydrogen economy challengesA Storage Capacity of 5-10 kg of hydrogen is needed to provide a range of 480 km for a electric-fuel cell car

60 L of gasoline for 480 km1 kg H2 = 4.02 L gasoline 15 kg H2

15 kg H2 Fuel cell eficiency = 2-3 5-10 kg H2

Hydrogen Onboard Storage DOE targets for 2010 Specific energy: 7.2 MJ/kg Gravimetric capacity: 7.2/120 kg H2/kg =0.06 kg H2/kg = 6 weight %

Energy density: 5.4 MJ/L Volumetric capacity: 5.4/120 kg H2/L = 0.045 kg H2/LNote: energy density of hydrogen is 120 MJ/kg for DOE, the LHV valueReversible Hydrogen Storage

Hydrogen Onboard Storage DOE targets for 2010 Operating temperature: 250 320 K Delivery pressure: 2.5 bars Refueling rate: 1.5 Kg/min or 7 minutes

Hydrogen Onboard Storage Reference gasoline car Mass fuel storage system: 74 Kg Volume fuel storage system: 107 L 75 L of gasoline or 55.4 Kg of gasoline 600 Km of autonomy 75 L gasoline 35 MJ/L gasoline = 2625 MJ Specific energy: 2625/74 + Fuel cell eficiency=2-5 7.2 MJ/kg Energy density: 2625/107 + Fuel cell eficiency=2-5 5.4 MJ/L

Hydrogen Onboard StorageNo current hydrogen storage technology meets the targets

Materials for Hydrogen Onboard StorageGOAL: Find new materials that fulfill the DOE targets for onboard hydrogen storage

Light Materials Porous MaterialsBinding energy of H2 to surface: 0.3-0.4 eV/molecule

Graphene Slitpores, Nanoporous Carbons, Carbide-Derived Carbons Li doped Graphene Slitpores Pd doped Graphene Slitpores Molecular Organic Frameworks, MOFs

Simulation of SlitporesSlitpore of width D: two parallel flat layers at distance DVan der Waals interaction of a molecule with the surfaceSingle LayerSlitpore

Relationship between pore size and shape and storage capacityModels for different pore shapesTwo parallel graphene layers:slitporeCNTs: cylidrical poresFullerenes: spherical pores

Storage capacities from the slitpore modelY. Gogotsi, et al. JACS 127, 16006 (2005)Jord-Beneyto,et al. Carbon 45,293 (2007)The measured storage capacities can be mimicked through slitpores of a single size or a combination of sizes

Pure Graphene Slitpores Optimal Slitpore Width: around 6

Volumetric and gravimetric goals ARE REACHED above 10 MPa at 300 K

Volumetric and gravimetric goals are reached at moderate pressures at 77 K and for slitpore widths larger than 5.5

Concavity and Li dopingelectronic density redistribution = dark +2, white -2 10- 4 e/au3Eb = 190-200 meVEb = 310-330 meV = green:+1, yellow -1, 10- 3 e/au3

Near Li inside: 0.30 eV/molecule!!A binding energy of 0.3-0.4 eV/H2 molecule is required for reversible uptake and release at room T Li et al., JCP 119, 2376-2385 (2003)Metal impurities increase binding energy and hydrogen storageBurgos, November 6th 2009, Project MeetingJCP 128, 144704 (2008) and JCP 123, 204721 (2003)

molecular adsorptionInteraction of H2 with Pd doped Graphene

Metal Organic Frameworks (MOFs) inorganic metal oxide cluster + organic linkerHigh Specific Surface Area, SSA = 2000 4700 m2/gHigh porosity volume = 80%High Specific Pore Volume = 1 cm3/g

Promise for hydrogen storage: tunable pore size: changing the linker tunable functionality: changing the metalYaghi & coworkers, Nature 402 276 (1999)MOFs: New family of highly porous, crystalline materials

MOF-5 structureMOF-5 cubered: Znblue: Ogray: Cwhite: Hcrystalline lattice: fccforms cubes:corners: OZn4 clustersedges: BDC organic linkersLattice parameter = 25.65 Porosity: two types of pores of 15 and 12

MOF-5 adsorption sitesDirect determination of the adsorption sites using inelastic neutron diffraction: Yaghi & coworkers, Science 300, 1127 (2003) 2 sites: one associated with the Zn and one with the BDC linker Yildirim & Hartman, Phys. Rev. Lett. (2005) 2 more sites are identified around the Zn-oxide cluster

Theoretical investigation find three main adsorption sites: CUP between three Ocore-Zn-O-C-O-Zn hexagons O3 plane above Zn Benzene

Adsorption around the Zn-oxide cluster should be responsible for the high storage capacity of MOFs

Comparison of MOFs with other nanoporous materialsAC from Linares, CDC from Gogotsi, MOF from Yaghi MOFs perform better than Activated Carbons and Carbide Derived Carbons at moderate pressures

New Catalysts made of Gold NanoclustersGold is noble metal, chemically inactive

But small clusters and nanostructures of gold have catalytic propertiesThey are very efficient for different chemical reactions of industrial interestGOAL: Design new catalysts made of gold nanoparticles for each specific chemical reaction

New Catalysts made of Gold NanoclustersWe have shown the selective oxidation of propene to form propylene oxide, used in the production of polyurethane

Model for Aun/Al2O3Clusters are supported on different surfaces and environments and these change their catalytic properties

Bimetallic Au-Ag alloy nanoparticles1ML of Ag1.83O on top of Au(111) corresponds to the situation of a bimetallic alloy with high Au concentration.Perspectives

- European Directive February 2003: take-back and treatment (recycling) of 4 kg of electronic waste per inhabitant and year Organization of the take-back Optimization of take-back costs Molecular dynamics algorithm applied to this economic problemParallel MD Algorithm applied to Economic Organization of Recycling

Parallel MD Algorithm applied to Economic Organization of Recycling

Interest of ResearchThe results of our research are useful for new technologies and materials related to important activity sectors of our region such as automotive and clean energies

- Ministerio de Educacin y Ciencia de Espaa y FSE, Programa Ramn y Cajal, http://www.mec.es/ciencia/jsp/plantilla.jsp?area=cajal&id=11 - Ministerio de Educacin y Ciencia de Espaa: Programa Nacional de Investigacin. Planes Nacionales I+D/I+D+I, MAT2005-06544-C03-01 and MAT2008-06483-C02-01

- Junta de Castilla y Len, Programa Gral. de Apoyo a Proyectos de Investigacin, VA039A05, VA017A08 and GR23AcknowledgmentsThanks for your attention

******Calculations with K=(2,2,1) and Spin polarization*Calculations with K=(2,2,1) and Spin polarization. The * means that with larger relaxations converts to two FACES*Calculations with K=(2,2,1) and Spin polarization. The * means that with larger relaxations converts to two FACES*