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Synthesis, Characterization and Application of Multiscale Porous Materials
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry.
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis work brings fresh insights and improved understanding of nanoscale materials through introducing new hybrid composites, 2D hexagonal in MCM-41 and 3D random interconnected structures of different materials, and application relevance for developing fields of science, such as fuel cells and solar cells.New types of porous materials and organometallic crystals have been prepared and characterized in detail. The porous materials have been used in several studies: as hosts to encapsulate metal-organic complexes; as catalyst supports and electrode materials in devices for alternative energy production. The utility of the new porous materials arises from their unique structural and surface chemical characteristics as demonstrated here using various experimental and theoretical approaches.New single crystal structures and arene-ligand exchange properties of f-block elements coordinated to ligand arene and halogallates are described in Paper I. These compounds have been incorporated into ordered 2D-hexagonal MCM-41 and polyhedral silica nanofoam (PNF-SiO2) matrices without significant change to the original porous architectures as described in Paper II and III. The resulting inorganic/organic hybrids exhibited enhanced luminescence activity relative to the pure crystalline complexes.A series of novel polyhedral carbon nanofoams (PNF-C´s) and inverse foams were prepared by nanocasting from PNF-SiO2’s. These are discussed in Paper IV. The synthesis conditions of PNF-C’s were systematically varied as a function of the filling ratio of carbon precursor and their structures compared using various characterization methods. The carbonaceous porous materials were further tested in Paper V and VI as possible catalysts and catalyst supports in counter- and working electrodes for solar- and fuel cell applications.

Place, publisher, year, edition, pages
Stockholm: KTH , 2010. , 58 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2010:3
National Category
Inorganic Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-27158ISBN: 978-91-7415-830-4 (print)OAI: oai:DiVA.org:kth-27158DiVA: diva2:375130
Public defence
2010-12-14, D3, Lindstedtsvägen 5, entréplan, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20101207Available from: 2010-12-07 Created: 2010-12-07 Last updated: 2010-12-08Bibliographically approved
List of papers
1. Mononuclear eta(6)-Arene Complexes of Lanthanides: One-Step Syntheses, Crystal Structures, and Arene Exchange
Open this publication in new window or tab >>Mononuclear eta(6)-Arene Complexes of Lanthanides: One-Step Syntheses, Crystal Structures, and Arene Exchange
2008 (English)In: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-1948, no 33, 5191-5195 p.Article in journal (Refereed) Published
Abstract [en]

Gallium(III) halides react with cerium(III), ytterbium(III), or dysprosium(III) halides in the presence of alkylated benzenes yielding mononuclear complexes of the general formula [Ln(eta(6)-arene)(GaX4)(3)]. The X-ray structures of [Ce(C6H5Me)- (GaCl4)(3)] (1), [Ce(p-C6H4Me2)(GaCl4)(3)]center dot 0.5(p-C6H4Me2) (2), [Yb(C6H5Me)(GaCl4)(3)] (3), [Yb(p-C6H4Me2)(GaCl4)(3)]center dot 0.5(p- C6H4Me2) (4), and [Dy(C6H5Me)(GaBr4)(3)] (5) were determined. Arene ligands in the cerium-toluene compound 1 can be substituted by polycyclic aromatic hydrocarbons (PAHs); the compounds [Ce(naphthalene) (GaCl4)(3)] (6) and [Ce(pyrene)(GaCl4)(3)]center dot 0.5(pyrene) (7) have been isolated and structurally characterized.

Identifiers
urn:nbn:se:kth:diva-18042 (URN)10.1002/ejic.200800807 (DOI)000261554300004 ()2-s2.0-56249127132 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
2. Incorporating mononuclear lanthanide organometallic species into mesoporous MCM-41 host material
Open this publication in new window or tab >>Incorporating mononuclear lanthanide organometallic species into mesoporous MCM-41 host material
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Mesoporous inorganic/organometallic hybrid materials incorporating rare earth metal complexes with mesoporous silica MCM-41 as a host material have been investigated. Lanthanide halides, Ce(III), Dy(III) and Yb(III) halides, in the presence of Ga(III) halides and aromatic solvents, such as toluene, p-xylene and 1,2,4-trichlorobenzene give complexes with the general formula of [Ln(η6-arene)(GaX4)3]. The incorporation of these species into MCM-41 has been performed via wet impregnation (WI) at room temperature and the resulting mixed systems have been investigated by powder X-ray diffraction (XRD), fluorescence spectroscopy and been further characterized by nitrogen physisorption and elemental analysis. The great diversity of possible coordination patterns through bond formation via the accessible hydroxyl groups of the silica surface can be described by Σ{Si(OH)n-x(O)x[Ln(η6-arene)(GaX4)3]}.

Keyword
MCM-41, Rare earth complex, Gallium halides, Aromatic solvent, Wet impregnation
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:kth:diva-27149 (URN)
Note
QC 20101207Available from: 2010-12-07 Created: 2010-12-07 Last updated: 2010-12-08Bibliographically approved
3. Study of [Dy(eta(6)-p-xylene)(GaCl4)(3)]-incorporated polyhedral silica nanofoam
Open this publication in new window or tab >>Study of [Dy(eta(6)-p-xylene)(GaCl4)(3)]-incorporated polyhedral silica nanofoam
2010 (English)In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 132, no 3, 480-486 p.Article in journal (Refereed) Published
Abstract [en]

Preparation and characterization of organometallic dysprosium complex embedded polyhedral silica nanofoam (PNE-SiO2) is reported. The nanoporous solid was obtained via a sol-gel process involving precipitation of polymer micelles, hydrolysis and condensation of silica by swelling of triblock copolymer template micelles of PEO-PPO-PEO at acidic pH using high oil concentration and fast stirring. Metal-complex incorporation was performed via wet impregnation (WI) at higher temperature, where the dysprosium complex is chemically bound to the silanol groups of the silica foam surface. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS) revealed that the particles of the organometallic complex are evenly distributed on the walls of the polyhedral cells, while nitrogen adsorption/desorption measurements (BET) verified that the characteristic meso- and macrocell structure of PNE-SiO2 composed of polyhedral cells of silica joined at mesosized windows are preserved also after incorporation.

Keyword
Polyhedral silica foam, Nanoporous materials, Wet impregnation, Dysprosium
Identifiers
urn:nbn:se:kth:diva-27151 (URN)10.1016/j.micromeso.2010.03.030 (DOI)000278629100023 ()2-s2.0-77953289093 (Scopus ID)
Note
QC 20101207Available from: 2010-12-07 Created: 2010-12-07 Last updated: 2017-12-11Bibliographically approved
4. Polyhedral carbon nanofoams with minimum surface area partitions produced using silica nanofoams as templates
Open this publication in new window or tab >>Polyhedral carbon nanofoams with minimum surface area partitions produced using silica nanofoams as templates
2010 (English)In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 48, no 11, 3121-3130 p.Article in journal (Refereed) Published
Abstract [en]

Polyhedral silica nanofoam (PNF-SiO2) analogues of dry soap froths with minimal surface area were used as templates for making polyhedral carbon nanofoams (PNF-C). Furfuryl alcohol or triblock copolymers were used as carbon sources. The volume of carbon precursor relative to the internal pore volume of PNF-SiO2's was systematically varied between 50% and 100% in order to investigate the effect of filling fraction on internal structure of the corresponding PNF-C's. Transmission electron microscopy, small-angle X-ray scattering and nitrogen physisorption were used to characterize the samples. To aid the interpretation of the experimental data, a model for X-ray scattering from spherical shells was used to approximate scattering from the polyhedral foam cells. PNF-C's cast from the PNF-SiO2's, displayed the characteristic Plateau borders of minimal surface area foams defining interconnected, slit-like pore systems at all filling fractions. At relatively high filling fractions, inverse foam structures were obtained with the slit-like pores systems interpenetrating aggregated, close-packed, relatively low density polyhedral carbon nanoparticles co-joined by carbon struts. At relatively low filling fractions, polyhedral carbon nanofoams with relatively thin, fused double-wall structures and interconnected polyhedral pore systems were obtained.

Keyword
MOLECULAR-SIEVES, ELECTRON CRYSTALLOGRAPHY, MESOPOROUS SILICA, ADSORPTION
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:kth:diva-27154 (URN)10.1016/j.carbon.2010.04.049 (DOI)000279984600013 ()2-s2.0-79955011698 (Scopus ID)
Funder
Swedish Research Council
Note
QC 20101207Available from: 2010-12-07 Created: 2010-12-07 Last updated: 2017-12-11Bibliographically approved
5. Large-Pore Sized Polyhedral Carbon Nanofoams as Counter Electrodes for Dye-Sensitized Solar Cells
Open this publication in new window or tab >>Large-Pore Sized Polyhedral Carbon Nanofoams as Counter Electrodes for Dye-Sensitized Solar Cells
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Polyhedral carbon nanofoams (PNF-C) of large mesoporous pore sizes were prepared using a hard-templating method and then investigated as low-temperature counterel ectrode materials in dye-sensitized solar cell (DSC). Photovoltaic parameters comprising short-circuit current (ISC), open-circuit voltage (VOC), fill factor (FF) and an overall light-to-electron conversion efficiency were evaluated for the fabricated cells. The superior structural features of the carbon foam materials; including large hollow mesoporous cells, large surface area and interconnected 3D framework; allow fast mass transport and enhanced activity toward I3- reduction as compared to microporous carbon counter electrode, used as a reference. Electrochemical Impedance Spectroscopy (EIS) analysis revealed decreased charge transfer resistance at the PNF-C counter electrode/electrolyte surface, thus improved energy conversion efficiency of 3.0 % in comparison with the standard carbon electrode of 1.3 %.

Identifiers
urn:nbn:se:kth:diva-27156 (URN)
Note
QC 20101207Available from: 2010-12-07 Created: 2010-12-07 Last updated: 2010-12-08Bibliographically approved
6. Polyhedral Carbon Nanofoams as Working Electrodes in PEM Fuel Cells
Open this publication in new window or tab >>Polyhedral Carbon Nanofoams as Working Electrodes in PEM Fuel Cells
(English)Manuscript (preprint) (Other (popular science, discussion, etc.))
Abstract [en]

Polyhedral carbon nanofoams (PNF-C´s) of various pore sizes were prepared and tested as working electrode support materials with relatively low Pt loading in Polymer Electrolyte Membrane Fuell Cell (PEMFs). The electrochemically active surface area (ECSA), carbon double layer capacitance (DLC), as well as fuel performance were evaluated by Cyclic Voltammetry (CV), Polarization Curves (PC) and Electrochemica lImpedance Spectroscopy (EIS) and compared to that of commercial working electrode material. The 3D interconnected, highly porous open structure, good electrical conductivity and unique surface characteristics of PNF-C´s offer increased mass transport and access to catalytic sites in fuel cells. One of the PNF-C supported Pt catalysts studied here out performed the standard commercial Pt/Vulcan catalyst due to its lower ionomer resistance and increased mass transport character.

National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:kth:diva-27157 (URN)
Note
QC 20101207Available from: 2010-12-07 Created: 2010-12-07 Last updated: 2010-12-08Bibliographically approved

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