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Loof D, Thüringer O, Zielasek V, Pranti AS, Lang W, Bäumer M. In-operando FTIR study of ligand-linked Pt nanoparticle networks employed as catalysts in hydrogen gas micro sensors. Nanoscale Adv 2024; 6:1436-1446. [PMID: 38419866 PMCID: PMC10898444 DOI: 10.1039/d3na00955f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Accepted: 01/31/2024] [Indexed: 03/02/2024]
Abstract
Microporous networks of Pt nanoparticles (NP) interlinked by aromatic diamines have recently shown prospects of application as hydrogen combustion catalysts in H2 gas microsensors. In particular with respect to long-term sensor performance, they outperformed plain Pt NP as catalysts. In this paper, electron microscopy and Fourier transform infrared (FTIR) spectroscopy data on the stability of p-phenylene diamine (PDA) and of the PDA-linked Pt NP network structure during catalyst activation and long-term sensor operation at elevated temperature (up to 120-180 °C) will be presented. For the first time, all data were collected directly from microsensor catalysts, and FTIR was performed in operando, i.e., during activation and sensor operation. While the data confirm high long-term catalyst activity far superior to that of plain Pt NP over 5 days of testing, they reveal that PDA fully decomposed during long-term sensor operation and that the network of discrete Pt nanoparticles changed to a sponge-like Pt nanostructure already during catalyst activation. These findings are at variance with previous work which assumed that stability of the PDA-linked Pt NP network is prerequisite for catalyst stability and performance.
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Affiliation(s)
- Daniel Loof
- University of Bremen, Institute of Applied and Physical Chemistry Leobener Str. 6 D-28359 Bremen Germany
| | - Oliver Thüringer
- University of Bremen, Institute of Applied and Physical Chemistry Leobener Str. 6 D-28359 Bremen Germany
| | - Volkmar Zielasek
- University of Bremen, Institute of Applied and Physical Chemistry Leobener Str. 6 D-28359 Bremen Germany
| | - Anmona Shabnam Pranti
- University of Bremen, Institute for Microsensors, Actuators and Systems (IMSAS) Otto-Hahn-Allee 1 D-28359 Bremen Germany
| | - Walter Lang
- University of Bremen, Institute for Microsensors, Actuators and Systems (IMSAS) Otto-Hahn-Allee 1 D-28359 Bremen Germany
| | - Marcus Bäumer
- University of Bremen, Institute of Applied and Physical Chemistry Leobener Str. 6 D-28359 Bremen Germany
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2
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Wittstock G, Bäumer M, Dononelli W, Klüner T, Lührs L, Mahr C, Moskaleva LV, Oezaslan M, Risse T, Rosenauer A, Staubitz A, Weissmüller J, Wittstock A. Nanoporous Gold: From Structure Evolution to Functional Properties in Catalysis and Electrochemistry. Chem Rev 2023; 123:6716-6792. [PMID: 37133401 DOI: 10.1021/acs.chemrev.2c00751] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Nanoporous gold (NPG) is characterized by a bicontinuous network of nanometer-sized metallic struts and interconnected pores formed spontaneously by oxidative dissolution of the less noble element from gold alloys. The resulting material exhibits decent catalytic activity for low-temperature, aerobic total as well as partial oxidation reactions, the oxidative coupling of methanol to methyl formate being the prototypical example. This review not only provides a critical discussion of ways to tune the morphology and composition of this material and its implication for catalysis and electrocatalysis, but will also exemplarily review the current mechanistic understanding of the partial oxidation of methanol using information from quantum chemical studies, model studies on single-crystal surfaces, gas phase catalysis, aerobic liquid phase oxidation, and electrocatalysis. In this respect, a particular focus will be on mechanistic aspects not well understood, yet. Apart from the mechanistic aspects of catalysis, best practice examples with respect to material preparation and characterization will be discussed. These can improve the reproducibility of the materials property such as the catalytic activity and selectivity as well as the scope of reactions being identified as the main challenges for a broader application of NPG in target-oriented organic synthesis.
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Affiliation(s)
- Gunther Wittstock
- Carl von Ossietzky University of Oldenburg, School of Mathematics and Science, Institute of Chemistry, D-26111 Oldenburg, Germany
| | - Marcus Bäumer
- University of Bremen, Institute for Applied and Physical Chemistry, 28359 Bremen, Germany
- University of Bremen, MAPEX Center for Materials and Processes, 28359 Bremen, Germany
| | - Wilke Dononelli
- University of Bremen, MAPEX Center for Materials and Processes, 28359 Bremen, Germany
- University of Bremen, Bremen Center for Computational Materials Science, Hybrid Materials Interfaces Group, Am Fallturm 1, Bremen 28359, Germany
| | - Thorsten Klüner
- Carl von Ossietzky University of Oldenburg, School of Mathematics and Science, Institute of Chemistry, D-26111 Oldenburg, Germany
| | - Lukas Lührs
- Hamburg University of Technology, Institute of Materials Physics and Technology, 21703 Hamburg, Germany
| | - Christoph Mahr
- University of Bremen, MAPEX Center for Materials and Processes, 28359 Bremen, Germany
- University of Bremen, Institute of Solid State Physics, Otto Hahn Allee 1, 28359 Bremen, Germany
| | - Lyudmila V Moskaleva
- University of the Free State, Department of Chemistry, P.O. Box 339, Bloemfontein 9300, South Africa
| | - Mehtap Oezaslan
- Technical University of Braunschweig Institute of Technical Chemistry, Technical Electrocatalysis Laboratory, Franz-Liszt-Strasse 35a, 38106 Braunschweig, Germany
| | - Thomas Risse
- Freie Universität Berlin, Institute of Chemistry and Biochemistry, Arnimallee 22, 14195 Berlin, Germany
| | - Andreas Rosenauer
- University of Bremen, MAPEX Center for Materials and Processes, 28359 Bremen, Germany
- University of Bremen, Institute of Solid State Physics, Otto Hahn Allee 1, 28359 Bremen, Germany
| | - Anne Staubitz
- University of Bremen, MAPEX Center for Materials and Processes, 28359 Bremen, Germany
- University of Bremen, Institute for Organic and Analytical Chemistry, Leobener Strasse 7, D-28359 Bremen, Germany
| | - Jörg Weissmüller
- Hamburg University of Technology, Institute of Materials Physics and Technology, 21703 Hamburg, Germany
- Helmholtz-Zentrum Hereon, Institute of Materials Mechanics, 21502 Geesthacht, Germany
| | - Arne Wittstock
- University of Bremen, MAPEX Center for Materials and Processes, 28359 Bremen, Germany
- University of Bremen, Institute for Organic and Analytical Chemistry, Leobener Strasse 7, D-28359 Bremen, Germany
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3
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Wild S, Mahr C, Rosenauer A, Risse T, Vasenkov S, Bäumer M. New Perspectives for Evaluating the Mass Transport in Porous Catalysts and Unfolding Macro- and Microkinetics. Catal Letters 2022; 153:3405-3422. [PMID: 37799191 PMCID: PMC10547662 DOI: 10.1007/s10562-022-04218-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Accepted: 11/11/2022] [Indexed: 12/13/2022]
Abstract
In this article we shed light on newly emerging perspectives to characterize and understand the interplay of diffusive mass transport and surface catalytic processes in pores of gas phase metal catalysts. As a case study, nanoporous gold, as an interesting example exhibiting a well-defined pore structure and a high activity for total and partial oxidation reactions is considered. PFG NMR (pulsed field gradient nuclear magnetic resonance) measurements allowed here for a quantitative evaluation of gas diffusivities within the material. STEM (scanning transmission electron microscopy) tomography furthermore provided additional insight into the structural details of the pore system, helping to judge which of its features are most decisive for slowing down mass transport. Based on the quantitative knowledge about the diffusion coefficients inside a porous catalyst, it becomes possible to disentangle mass transport contributions form the measured reaction kinetics and to determine the kinetic rate constant of the underlying catalytic surface reaction. In addition, predictions can be made for an improved effectiveness of the catalyst, i.e., optimized conversion rates. This approach will be discussed at the example of low-temperature CO oxidation, efficiently catalysed by npAu at 30 °C. The case study shall reveal that novel porous materials exhibiting well-defined micro- and mesoscopic features and sufficient catalytic activity, in combination with modern techniques to evaluate diffusive transport, offer interesting new opportunities for an integral understanding of catalytic processes. Graphical Abstract
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Affiliation(s)
- Stefan Wild
- Institute for Applied and Physical Chemistry, University of Bremen, 28359 Bremen, Germany
- MAPEX Center of Materials and Processes, University of Bremen, 28359 Bremen, Germany
| | - Christoph Mahr
- MAPEX Center of Materials and Processes, University of Bremen, 28359 Bremen, Germany
- Institute of Solid State Physics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany
| | - Andreas Rosenauer
- MAPEX Center of Materials and Processes, University of Bremen, 28359 Bremen, Germany
- Institute of Solid State Physics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany
| | - Thomas Risse
- Institute of Chemistry and Biochemistry, Free University Berlin, 14195 Berlin, Germany
| | - Sergey Vasenkov
- Department of Chemical Engineering, University of Florida, Gainesville, FL 32611 USA
| | - Marcus Bäumer
- Institute for Applied and Physical Chemistry, University of Bremen, 28359 Bremen, Germany
- MAPEX Center of Materials and Processes, University of Bremen, 28359 Bremen, Germany
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4
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Baniani A, Wild S, Forman EM, Risse T, Vasenkov S, Bäumer M. Disentangling catalysis and mass transport: Using diffusion measurements by pulsed field gradient NMR to reveal the microkinetics of CO oxidation over nanoporous gold. J Catal 2022. [DOI: 10.1016/j.jcat.2022.08.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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5
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Weber S, Zimmermann RT, Bremer J, Abel KL, Poppitz D, Prinz N, Ilsemann J, Wendholt S, Yang Q, Pashminehazar R, Monaco F, Cloetens P, Huang X, Kübel C, Kondratenko E, Bauer M, Bäumer M, Zobel M, Gläser R, Sundmacher K, Sheppard TL. Digitization in Catalysis Research: Towards a Holistic Description of a Ni/Al2O3 Reference Catalyst for CO2 Methanation. ChemCatChem 2022. [DOI: 10.1002/cctc.202101878] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Sebastian Weber
- Karlsruhe Institute of Technology: Karlsruher Institut fur Technologie Institute of Catalysis Research and Technology GERMANY
| | - Ronny T. Zimmermann
- Otto-von-Guericke-University Magdeburg: Otto von Guericke Universitat Magdeburg Institute of Process Engineering GERMANY
| | - Jens Bremer
- Max Planck Institute for Dynamics of Complex Technical Systems: Max-Planck-Institut fur Dynamik komplexer technischer Systeme Department of Process Systems Engineering GERMANY
| | - Ken L. Abel
- Leipzig University: Universitat Leipzig Institute of Chemical Technology GERMANY
| | - David Poppitz
- Leipzig University: Universitat Leipzig Institute of Chemical Technology GERMANY
| | - Nils Prinz
- RWTH Aachen University: Rheinisch-Westfalische Technische Hochschule Aachen Institute of Crystallography GERMANY
| | - Jan Ilsemann
- University of Bremen: Universitat Bremen Institute of Applied and Physical Chemistry GERMANY
| | - Sven Wendholt
- Paderborn University: Universitat Paderborn Faculty of Science and Center for Sustainable Systems Design GERMANY
| | - Qingxin Yang
- Leibniz Institute for Catalysis: Leibniz-Institut fur Katalyse eV LIKAT GERMANY
| | - Reihaneh Pashminehazar
- Karlsruhe Institute of Technology: Karlsruher Institut fur Technologie Institute for Chemical Technology and Polymer Chemistry GERMANY
| | | | - Peter Cloetens
- European Synchrotron Radiation Facility: ESRF ESRF FRANCE
| | - Xiaohui Huang
- Karlsruhe Institute of Technology: Karlsruher Institut fur Technologie Institute of Nanotechnology GERMANY
| | - Christian Kübel
- Karlsruhe Institute of Technology: Karlsruher Institut fur Technologie Institute of Nanotechnology GERMANY
| | - Evgenii Kondratenko
- Leibniz Institute for Catalysis: Leibniz-Institut fur Katalyse eV LIKAT GERMANY
| | - Matthias Bauer
- Paderborn University: Universitat Paderborn Faculty of Science and Center for Sustainable Systems Design GERMANY
| | - Marcus Bäumer
- University of Bremen: Universitat Bremen Institute of Applied and Physical Chemistry GERMANY
| | - Mirijam Zobel
- RWTH Aachen University: Rheinisch-Westfalische Technische Hochschule Aachen Institute of Crystallography GERMANY
| | - Roger Gläser
- Leipzig University: Universitat Leipzig Institute of Chemical Technology GERMANY
| | - Kai Sundmacher
- Otto-von-Guericke-University Magdeburg: Otto von Guericke Universitat Magdeburg Institute of Process Engineering GERMANY
| | - Thomas Lennon Sheppard
- Karlsruher Institut fur Technologie Institute for Chemical Technology and Polymer Chemistry Engesserstrasse 20 76131 Karlsruhe GERMANY
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6
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Li S, Olaniyan O, Carroll LL, Bäumer M, Moskaleva LV. Catalytic Activity of 1D Chains of Gold Oxide on a Stepped Gold Surface from Density Functional Theory. Phys Chem Chem Phys 2022; 24:28853-28863. [DOI: 10.1039/d2cp03524c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The rich surface chemistry of gold at the nanoscale has made it an important catalyst for low-temperature applications. Recent studies point to the possible role of self-organized structures formed by...
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7
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Loof D, Thüringer O, Schowalter M, Mahr C, Pranti AS, Lang W, Rosenauer A, Zielasek V, Kunz S, Bäumer M. Synthesis and Characterization of Ligand-Linked Pt Nanoparticles: Tunable, Three-Dimensional, Porous Networks for Catalytic Hydrogen Sensing. ChemistryOpen 2021; 10:697-712. [PMID: 34251087 PMCID: PMC8274309 DOI: 10.1002/open.202000344] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 06/03/2021] [Indexed: 11/25/2022] Open
Abstract
Porous networks of Pt nanoparticles interlinked by bifunctional organic ligands have shown high potential as catalysts in micro-machined hydrogen gas sensors. By varying the ligand among p-phenylenediamine, benzidine, 4,4''-diamino-p-terphenyl, 1,5-diaminonaphthalene, and trans-1,4-diaminocyclohexane, new variants of such networks were synthesized. Inter-particle distances within the networks, determined via transmission electron microscopy tomography, varied from 0.8 to 1.4 nm in accordance with the nominal length of the respective ligand. While stable structures with intact and coordinatively bonded diamines were formed with all ligands, aromatic diamines showed superior thermal stability. The networks exhibited mesoporous structures depending on ligand and synthesis strategy and performed well as catalysts in hydrogen gas microsensors. They demonstrate the possibility of deliberately tuning micro- and mesoporosity and thereby transport properties and steric demands by choice of the right ligand also for other applications in heterogeneous catalysis.
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Affiliation(s)
- Daniel Loof
- Institute of Applied and Physical ChemistryUniversity of BremenLeobener Str. 628359BremenGermany
| | - Oliver Thüringer
- Institute of Applied and Physical ChemistryUniversity of BremenLeobener Str. 628359BremenGermany
| | - Marco Schowalter
- Institute of Solid-State PhysicsUniversity of BremenOtto-Hahn-Allee 128359BremenGermany
| | - Christoph Mahr
- Institute of Solid-State PhysicsUniversity of BremenOtto-Hahn-Allee 128359BremenGermany
| | - Anmona Shabnam Pranti
- Institute for Microsensors, -actuators and -systems (IMSAS)University of BremenOtto-Hahn-Allee 128359BremenGermany
| | - Walter Lang
- Institute for Microsensors, -actuators and -systems (IMSAS)University of BremenOtto-Hahn-Allee 128359BremenGermany
| | - Andreas Rosenauer
- Institute of Solid-State PhysicsUniversity of BremenOtto-Hahn-Allee 128359BremenGermany
| | - Volkmar Zielasek
- Institute of Applied and Physical ChemistryUniversity of BremenLeobener Str. 628359BremenGermany
| | - Sebastian Kunz
- Institute of Applied and Physical ChemistryUniversity of BremenLeobener Str. 628359BremenGermany
- Südzucker AGCentral Department Research, Development, and Services (CRDS)Wormser Strasse 1167283ObrigheimGermany
| | - Marcus Bäumer
- Institute of Applied and Physical ChemistryUniversity of BremenLeobener Str. 628359BremenGermany
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8
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Stahl J, Ilsemann J, Pokhrel S, Schowalter M, Tessarek C, Rosenauer A, Eickhoff M, Bäumer M, Mädler L. Comparing Co‐catalytic Effects of ZrO
x
, SmO
x
, and Pt on CO
x
Methanation over Co‐based Catalysts Prepared by Double Flame Spray Pyrolysis. ChemCatChem 2021. [DOI: 10.1002/cctc.202001998] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Jakob Stahl
- Faculty of Production Engineering University of Bremen Badgasteiner Straße 1 28359 Bremen Germany
| | - Jan Ilsemann
- Institute of Applied and Physical Chemistry and Center for Environmental Research (UFT) University of Bremen Leobener Straße 6 28359 Bremen Germany
| | - Suman Pokhrel
- Faculty of Production Engineering University of Bremen Badgasteiner Straße 1 28359 Bremen Germany
- Leibniz Institute for Materials Engineering IWT Badgasteiner Straße 3 28359 Bremen Germany
| | - Marco Schowalter
- Institute of Solid State Physics University of Bremen Otto-Hahn-Allee 1 28359 Bremen Germany
| | - Christian Tessarek
- Institute of Solid State Physics University of Bremen Otto-Hahn-Allee 1 28359 Bremen Germany
| | - Andreas Rosenauer
- Institute of Solid State Physics University of Bremen Otto-Hahn-Allee 1 28359 Bremen Germany
- MAPEX Center for Materials and Processes University of Bremen Postfach 330 440 Germany
| | - Martin Eickhoff
- Institute of Solid State Physics University of Bremen Otto-Hahn-Allee 1 28359 Bremen Germany
- MAPEX Center for Materials and Processes University of Bremen Postfach 330 440 Germany
| | - Marcus Bäumer
- Institute of Applied and Physical Chemistry and Center for Environmental Research (UFT) University of Bremen Leobener Straße 6 28359 Bremen Germany
- MAPEX Center for Materials and Processes University of Bremen Postfach 330 440 Germany
| | - Lutz Mädler
- Faculty of Production Engineering University of Bremen Badgasteiner Straße 1 28359 Bremen Germany
- Leibniz Institute for Materials Engineering IWT Badgasteiner Straße 3 28359 Bremen Germany
- MAPEX Center for Materials and Processes University of Bremen Postfach 330 440 Germany
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9
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Jones AS, Aziz D, Ilsemann J, Bäumer M, Hagelin-Weaver H. Effects of low molar concentrations of low-valence dopants on samarium oxide xerogels in the oxidative coupling of methane. Catal Today 2021. [DOI: 10.1016/j.cattod.2020.05.062] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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10
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Ilsemann J, Murshed MM, Gesing TM, Kopyscinski J, Bäumer M. On the support dependency of the CO 2 methanation – decoupling size and support effects. Catal Sci Technol 2021. [DOI: 10.1039/d1cy00399b] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The influence of the support basicity, according to the Lewis and Brønsted definition, was investigated for the CO2 methanation over isostructural Ru catalysts.
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Affiliation(s)
- Jan Ilsemann
- Institute of Applied and Physical Chemistry
- University of Bremen
- 28359 Bremen
- Germany
| | - Mangir M. Murshed
- Institute of Inorganic Chemistry and Crystallography
- University of Bremen
- 28359 Bremen
- Germany
- MAPEX Center for Materials and Processes
| | - Thorsten M. Gesing
- Institute of Inorganic Chemistry and Crystallography
- University of Bremen
- 28359 Bremen
- Germany
- MAPEX Center for Materials and Processes
| | - Jan Kopyscinski
- Catalytic Process Engineering
- McGill University
- Montreal
- Canada
| | - Marcus Bäumer
- Institute of Applied and Physical Chemistry
- University of Bremen
- 28359 Bremen
- Germany
- MAPEX Center for Materials and Processes
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11
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Li S, Li Y, Bäumer M, Moskaleva LV. Assessment of PBE+U and HSE06 methods and determination of optimal parameter U for the structural and energetic properties of rare earth oxides. J Chem Phys 2020; 153:164710. [PMID: 33138436 DOI: 10.1063/5.0024499] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Rare earth oxides are attracting increasing interest as a relatively unexplored group of materials with potential applications in heterogeneous catalysis and electrocatalysis; therefore, a credible and universal computational approach is needed for modeling their reactivity. In this work, we systematically assessed the performance of the PBE+U method against the results of the hybrid HSE06 method with respect to the description of structural parameters and energetic properties of the selected hexagonal lanthanide sesquioxides and the cubic fluorite-type cerium dioxide. In addition, we evaluated the performance of PBE+U in describing the electronic structure and adsorption properties of the CeO2(111) and Nd2O3(0001) surfaces. The HSE06 method reproduces rather well the lattice parameters and selected energetic properties with respect to the experimental values. The PBE+U method is able to reproduce the results of HSE06 or the experimental values only if the U parameter is selected from an appropriate range of values. The U value around 3 eV gives the best description of the lattice parameters of most bulk oxides. 2 eV-3 eV is also found to be the optimal range of U for the reaction energies of bulk La2O3, Ce2O3, Nd2O3, Er2O3, and Ho2O3. U = 1 eV gives the best results for Pr2O3, Pm2O3, Eu2O3, Tm2O3, and Lu2O3, whereas Gd2O3 could not be accurately described by the PBE+U method. The U values (∼3 eV) found optimal for most bulk oxides also work well in the calculations of adsorption of small molecules on Nd2O3(0001) and CeO2(111), although larger U values are required to obtain sufficient localization of 4f electrons.
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Affiliation(s)
- Shikun Li
- Institute of Applied and Physical Chemistry, Faculty 02, University of Bremen, 28359 Bremen, Germany
| | - Yong Li
- Institute of Applied and Physical Chemistry, Faculty 02, University of Bremen, 28359 Bremen, Germany
| | - Marcus Bäumer
- Institute of Applied and Physical Chemistry, Faculty 02, University of Bremen, 28359 Bremen, Germany
| | - Lyudmila V Moskaleva
- Institute of Applied and Physical Chemistry, Faculty 02, University of Bremen, 28359 Bremen, Germany
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12
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Neumann S, Doebler HH, Keil S, Erdt AJ, Gutsche C, Borchert H, Kolny-Olesiak J, Parisi J, Bäumer M, Kunz S. Effects of Particle Size on Strong Metal–Support Interactions Using Colloidal “Surfactant-Free” Pt Nanoparticles Supported on Fe 3O 4. ACS Catal 2020. [DOI: 10.1021/acscatal.9b04367] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sarah Neumann
- Institute of Applied and Physical Chemistry (IAPC), Center for Environmental Research and Sustainable Technology, University of Bremen, Leobener Strasse 6, 28359 Bremen, Germany
- MAPEX Center for Materials and Processes, University of Bremen, Bibliothekstrasse 1, 28350 Bremen, Germany
| | - Hans Hannes Doebler
- Institute of Applied and Physical Chemistry (IAPC), Center for Environmental Research and Sustainable Technology, University of Bremen, Leobener Strasse 6, 28359 Bremen, Germany
- MAPEX Center for Materials and Processes, University of Bremen, Bibliothekstrasse 1, 28350 Bremen, Germany
| | - Simona Keil
- Institute of Applied and Physical Chemistry (IAPC), Center for Environmental Research and Sustainable Technology, University of Bremen, Leobener Strasse 6, 28359 Bremen, Germany
- MAPEX Center for Materials and Processes, University of Bremen, Bibliothekstrasse 1, 28350 Bremen, Germany
| | - Alexandra J. Erdt
- Energy and Semiconductor Research Laboratory, Department of Physics, Carl von Ossietzky University of Oldenburg, 26111 Oldenburg, Germany
| | - Christian Gutsche
- Energy and Semiconductor Research Laboratory, Department of Physics, Carl von Ossietzky University of Oldenburg, 26111 Oldenburg, Germany
| | - Holger Borchert
- Energy and Semiconductor Research Laboratory, Department of Physics, Carl von Ossietzky University of Oldenburg, 26111 Oldenburg, Germany
| | - Joanna Kolny-Olesiak
- Energy and Semiconductor Research Laboratory, Department of Physics, Carl von Ossietzky University of Oldenburg, 26111 Oldenburg, Germany
| | - Jürgen Parisi
- Energy and Semiconductor Research Laboratory, Department of Physics, Carl von Ossietzky University of Oldenburg, 26111 Oldenburg, Germany
| | - Marcus Bäumer
- Institute of Applied and Physical Chemistry (IAPC), Center for Environmental Research and Sustainable Technology, University of Bremen, Leobener Strasse 6, 28359 Bremen, Germany
- MAPEX Center for Materials and Processes, University of Bremen, Bibliothekstrasse 1, 28350 Bremen, Germany
| | - Sebastian Kunz
- Institute of Applied and Physical Chemistry (IAPC), Center for Environmental Research and Sustainable Technology, University of Bremen, Leobener Strasse 6, 28359 Bremen, Germany
- MAPEX Center for Materials and Processes, University of Bremen, Bibliothekstrasse 1, 28350 Bremen, Germany
- Südzucker AG, Central Department Research, Development, and Services (CRDS), Wormser Strasse 11, 67283 Obrigheim, Germany
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13
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Li Y, Li S, Bäumer M, Ivanova-Shor EA, Moskaleva LV. What Changes on the Inverse Catalyst? Insights from CO Oxidation on Au-Supported Ceria Nanoparticles Using Ab Initio Molecular Dynamics. ACS Catal 2020. [DOI: 10.1021/acscatal.9b05175] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yong Li
- Institute of Applied and Physical Chemistry and Center for Environmental Research and Sustainable Technology, University of Bremen, Bremen 28359, Germany
| | - Shikun Li
- Institute of Applied and Physical Chemistry and Center for Environmental Research and Sustainable Technology, University of Bremen, Bremen 28359, Germany
| | - Marcus Bäumer
- Institute of Applied and Physical Chemistry and Center for Environmental Research and Sustainable Technology, University of Bremen, Bremen 28359, Germany
| | - Elena A. Ivanova-Shor
- Institute of Chemistry and Chemical Technology SB RAS, Federal Research Center “Krasnoyarsk Scientific Center SB RAS”, Krasnoyarsk 660036, Russia
| | - Lyudmila V. Moskaleva
- Institute of Applied and Physical Chemistry and Center for Environmental Research and Sustainable Technology, University of Bremen, Bremen 28359, Germany
- Department of Chemistry, University of the Free State, P.O. Box 339, Bloemfontein 9300, South Africa
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14
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Pranti AS, Loof D, Kunz S, Zielasek V, Bäumer M, Lang W. Design and Fabrication Challenges of a Highly Sensitive Thermoelectric-Based Hydrogen Gas Sensor. Micromachines (Basel) 2019; 10:mi10100650. [PMID: 31569728 PMCID: PMC6843170 DOI: 10.3390/mi10100650] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Revised: 09/24/2019] [Accepted: 09/24/2019] [Indexed: 11/16/2022]
Abstract
This paper presents a highly sensitive thermoelectric sensor for catalytic combustible gas detection. The sensor contains two low-stress (+176 MPa) membranes of a combination of stoichiometric and silicon-rich silicon nitride that makes them chemically and thermally stable. The complete fabrication process with details, especially the challenges and their solutions, is discussed elaborately. In addition, a comprehensive evaluation of design criteria and a comparative analysis of different sensor designs are performed with respect to the homogeneity of the temperature field on the membrane, power consumption, and thermal sensitivity. Evaluating the respective tradeoffs, the best design is selected. The selected sensor has a linear thermal characteristic with a sensitivity of 6.54 mV/K. Additionally, the temperature profile on the membrane is quite homogeneous (20% root mean standard deviation), which is important for the stability of the catalytic layer. Most importantly, the sensor with a ligand (p-Phenylenediamine (PDA))-linked platinum nanoparticles catalyst shows exceptionally high response to hydrogen gas, i.e., 752 mV at 2% concentration.
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Affiliation(s)
- Anmona Shabnam Pranti
- IMSAS-Institute for Microsensors, -actuators and -systems, University of Bremen, 28359 Bremen, Germany.
| | - Daniel Loof
- IAPC-Institute of Applied and Physical Chemistry, University of Bremen, 28359 Bremen, Germany.
| | - Sebastian Kunz
- IAPC-Institute of Applied and Physical Chemistry, University of Bremen, 28359 Bremen, Germany.
| | - Volkmar Zielasek
- IAPC-Institute of Applied and Physical Chemistry, University of Bremen, 28359 Bremen, Germany.
| | - Marcus Bäumer
- IAPC-Institute of Applied and Physical Chemistry, University of Bremen, 28359 Bremen, Germany.
| | - Walter Lang
- IMSAS-Institute for Microsensors, -actuators and -systems, University of Bremen, 28359 Bremen, Germany.
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15
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Ilsemann J, Straß‐Eifert A, Friedland J, Kiewidt L, Thöming J, Bäumer M, Güttel R. Cobalt@Silica Core‐Shell Catalysts for Hydrogenation of CO/CO
2
Mixtures to Methane. ChemCatChem 2019. [DOI: 10.1002/cctc.201900916] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Jan Ilsemann
- Institute of Applied and Physical ChemistryUniversity of Bremen Bremen 28359 Germany
| | | | - Jens Friedland
- Institute of Chemical EngineeringUlm University Ulm 89081 Germany
| | - Lars Kiewidt
- Institute of Chemical EngineeringUniversity of Bremen Bremen 28359 Germany
| | - Jorg Thöming
- Institute of Chemical EngineeringUniversity of Bremen Bremen 28359 Germany
| | - Marcus Bäumer
- Institute of Applied and Physical ChemistryUniversity of Bremen Bremen 28359 Germany
| | - Robert Güttel
- Institute of Chemical EngineeringUlm University Ulm 89081 Germany
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16
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Affiliation(s)
- Jan Ilsemann
- University of BremenInstitute of Applied and Physical Chemistry 28359 Bremen Germany
| | - Andrea Sonström
- University of TübingenInstitute of Inorganic Chemistry 72076 Tübingen Germany
| | - Thorsten M. Gesing
- University of BremenInstitute of Inorganic Chemistry and Crystallography 28359 Bremen Germany
- University of BremenMAPEX Center for Materials and Processes 28359 Bremen Germany
| | - Reiner Anwander
- University of TübingenInstitute of Inorganic Chemistry 72076 Tübingen Germany
| | - Marcus Bäumer
- University of BremenInstitute of Applied and Physical Chemistry 28359 Bremen Germany
- University of BremenMAPEX Center for Materials and Processes 28359 Bremen Germany
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17
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Shi J, Wittstock A, Mahr C, Murshed MM, Gesing TM, Rosenauer A, Bäumer M. Nanoporous gold functionalized with praseodymia-titania mixed oxides as a stable catalyst for the water-gas shift reaction. Phys Chem Chem Phys 2019; 21:3278-3286. [PMID: 30681677 DOI: 10.1039/c8cp06040a] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Dealloyed nanoporous metals hold great promise in the field of heterogeneous catalysis; however their tendency to coarsen at elevated temperatures or under catalytic reaction conditions sometimes limit further applications. Here, we report on a highly stable nanoporous gold catalyst (npAu) functionalized with praseodymia-titania mixed oxides as synthesized by a sol-gel method. Specifically, we used aberration-corrected transmission electron microscopy to study the morphology and the interface between the oxide deposits and the npAu substrate at the atomic level. Based on electron energy loss spectroscopy (EELS), it is concluded that Pr-TiOx mixed oxides form a solid solution. Flow reactor tests reveal that the Pr-TiOx functionalized nanoporous gold is not only highly active but also very stable for the water gas shift reaction in a large temperature range (180-400 °C). Our results demonstrate the potential of engineering the compositions of oxides coatings on npAu for advanced functional systems.
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Affiliation(s)
- Junjie Shi
- Institute of Applied and Physical Chemistry and Center for Environmental Research and Sustainable Technology, University of Bremen, Leobener Str. 6, 28359 Bremen, Germany.
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18
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Lackmann A, Bäumer M, Wittstock G, Wittstock A. Independent control over residual silver content of nanoporous gold by galvanodynamically controlled dealloying. Nanoscale 2018; 10:17166-17173. [PMID: 30187073 DOI: 10.1039/c8nr03699c] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
A new procedure was developed and characterized for the galvanodynamically controlled dealloying (GCD) of AuxAg100-x alloys to obtain nanoporous gold (npAu) mainly as an unsupported catalyst material for partial oxidation of alcohols. Such catalysts require residual Ag content of less than 1 at%. GCD was compared to the preparation of npAu by potentiostatically controlled deallyoing (PCD) and free corrosion (FC). The main advantage of GCD is the ability to obtain npAu with a predetermined residual Ag content including residual Ag contents below 1 at% while retarding the coarsening of the ligaments. For PCD and FC, there is a strong increase of ligament size with decreasing residual Ag content because the longer times required for dealloying unavoidably lead to coarsening of the npAu structure. On the other hand, GCD also prevented too high initial current density that leads to cracking of the samples and prevents formation of mechanically stable monoliths. GCD tolerates different compositions of the starting alloy for AuxAg100-x within the tested composition range (20 at% ≤ xAu ≤ 30 at%). The samples obtained by GCD were tested for methanol and ethanol oxidation and showed favorable characteristics for partial oxidation of methanol to methyl formate and of ethanol to ethyl acetate.
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Affiliation(s)
- Anastasia Lackmann
- Institute of Applied and Physical Chemistry and Center for Environmental Research and Sustainable Technology, University Bremen, Leobener Str. UFT, 28359 Bremen, Germany.
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19
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20
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Shi J, Mahr C, Murshed MM, Gesing TM, Rosenauer A, Bäumer M, Wittstock A. Steam reforming of methanol over oxide decorated nanoporous gold catalysts: a combined in situ FTIR and flow reactor study. Phys Chem Chem Phys 2018; 19:8880-8888. [PMID: 28294235 DOI: 10.1039/c6cp08849j] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Methanol as a green and renewable resource can be used to generate hydrogen by reforming, i.e., its catalytic oxidation with water. In combination with a fuel cell this hydrogen can be converted into electrical energy, a favorable concept, in particular for mobile applications. Its realization requires the development of novel types of structured catalysts, applicable in small scale reactor designs. Here, three different types of such catalysts were investigated for the steam reforming of methanol (SRM). Oxides such as TiO2 and CeO2 and mixtures thereof (Ce1Ti2Ox) were deposited inside a bulk nanoporous gold (npAu) material using wet chemical impregnation procedures. Transmission electron and scanning electron microscopy reveal oxide nanoparticles (1-2 nm in size) abundantly covering the strongly curved surface of the nanoporous gold host (ligaments and pores on the order of 40 nm in size). These catalysts were investigated in a laboratory scaled flow reactor. First conversion of methanol was detected at 200 °C. The measured turn over frequency at 300 °C of the CeOx/npAu catalyst was 0.06 s-1. Parallel investigation by in situ infrared spectroscopy (DRIFTS) reveals that the activation of water and the formation of OHads are the key to the activity/selectivity of the catalysts. While all catalysts generate sufficient OHads to prevent complete dehydrogenation of methanol to CO, only the most active catalysts (e.g., CeOx/npAu) show direct reaction with formic acid and its decomposition to CO2 and H2. The combination of flow reactor studies and in operando DRIFTS, thus, opens the door to further development of this type of catalyst.
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Affiliation(s)
- J Shi
- Institute of Applied and Physical Chemistry and Center for Environmental Research and Sustainable Technology, University Bremen, Leobener Str. UFT, 28359 Bremen, Germany.
| | - C Mahr
- Institute of Solid State Physics, University Bremen, Bremen, Germany
| | - M M Murshed
- Solid State Chemical Crystallography, Institute of Inorganic Chemistry and Crystallography/FB02, University Bremen, Leobener Str. NW 2, 28359, Bremen, Germany
| | - T M Gesing
- Solid State Chemical Crystallography, Institute of Inorganic Chemistry and Crystallography/FB02, University Bremen, Leobener Str. NW 2, 28359, Bremen, Germany
| | - A Rosenauer
- Institute of Solid State Physics, University Bremen, Bremen, Germany
| | - M Bäumer
- Institute of Applied and Physical Chemistry and Center for Environmental Research and Sustainable Technology, University Bremen, Leobener Str. UFT, 28359 Bremen, Germany.
| | - A Wittstock
- Institute of Applied and Physical Chemistry and Center for Environmental Research and Sustainable Technology, University Bremen, Leobener Str. UFT, 28359 Bremen, Germany.
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21
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Dreher W, Bardenhagen I, Huang L, Bäumer M. On the suppression of background signals originating from NMR hardware components. Application to zero echo time imaging and relaxation time analysis. Magn Reson Imaging 2016; 34:264-70. [DOI: 10.1016/j.mri.2015.10.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Revised: 10/15/2015] [Accepted: 10/17/2015] [Indexed: 10/22/2022]
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22
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Schubert M, Pokhrel S, Thomé A, Zielasek V, Gesing TM, Roessner F, Mädler L, Bäumer M. Highly active Co–Al2O3-based catalysts for CO2 methanation with very low platinum promotion prepared by double flame spray pyrolysis. Catal Sci Technol 2016. [DOI: 10.1039/c6cy01252c] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Alumina supported Co catalysts are often promoted with noble metals to improve their reducibility and provide a high number of metallic Co sites. A flame spray pyrolysis based approach for the preparation is described which allows a fine dispersion of Pt so that very low concentrations are necessary.
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Affiliation(s)
- Miriam Schubert
- Institute of Applied and Physical Chemistry
- University of Bremen
- Germany
| | - Suman Pokhrel
- Foundation Institute of Materials Science (IWT)
- Department of Production Engineering
- University of Bremen
- Germany
| | - Andreas Thomé
- Institute of Chemistry
- Carl v. Ossietzky University of Oldenburg
- Germany
| | - Volkmar Zielasek
- Institute of Applied and Physical Chemistry
- University of Bremen
- Germany
- MAPEX Center for Materials and Processes
- University of Bremen
| | - Thorsten M. Gesing
- Solid State Chemical Crystallography
- Institute of Inorganic Chemistry and Crystallography
- University of Bremen
- Germany
- MAPEX Center for Materials and Processes
| | - Frank Roessner
- Institute of Chemistry
- Carl v. Ossietzky University of Oldenburg
- Germany
| | - Lutz Mädler
- Foundation Institute of Materials Science (IWT)
- Department of Production Engineering
- University of Bremen
- Germany
- MAPEX Center for Materials and Processes
| | - Marcus Bäumer
- Institute of Applied and Physical Chemistry
- University of Bremen
- Germany
- MAPEX Center for Materials and Processes
- University of Bremen
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23
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Abstract
Applications such as catalytic gas sensing require a high density of catalytically active sites at low total heat capacity. One way to achieve this goal is the molecular linkage of colloidal nanoparticles with bifunctional ligands resulting in 3D-porous networks. The catalytic properties of such structures were investigated in a thermoelectric hydrogen sensor.
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Affiliation(s)
- Eva Morsbach
- IAPC (Institute of Applied and Physical Chemistry) & Center for Environmental Research and Sustainable Technology
- University of Bremen
- 28359 Bremen
- Germany
| | - Sebastian Kunz
- IAPC (Institute of Applied and Physical Chemistry) & Center for Environmental Research and Sustainable Technology
- University of Bremen
- 28359 Bremen
- Germany
| | - Marcus Bäumer
- IAPC (Institute of Applied and Physical Chemistry) & Center for Environmental Research and Sustainable Technology
- University of Bremen
- 28359 Bremen
- Germany
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24
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Shi J, Mahr C, Murshed MM, Zielasek V, Rosenauer A, Gesing TM, Bäumer M, Wittstock A. A versatile sol–gel coating for mixed oxides on nanoporous gold and their application in the water gas shift reaction. Catal Sci Technol 2016. [DOI: 10.1039/c5cy02205c] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Ceria–titania mixed oxides on a structured nanoporous gold support result in highly active and durable catalysts for the water-gas shift reaction.
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Affiliation(s)
- Junjie Shi
- Institute of Applied and Physical Chemistry and Center for Environmental Research and Sustainable Technology
- University Bremen
- Bremen
- Germany
- MAPEX Center for Materials and Processes
| | - Christoph Mahr
- Institute of Solid State Physics
- University Bremen
- Bremen
- Germany
- MAPEX Center for Materials and Processes
| | - M. Mangir Murshed
- Solid State Chemical Crystallography, Institute of Inorganic Chemistry and Crystallography/FB02
- University Bremen
- Bremen
- Germany
- MAPEX Center for Materials and Processes
| | - Volkmar Zielasek
- Institute of Applied and Physical Chemistry and Center for Environmental Research and Sustainable Technology
- University Bremen
- Bremen
- Germany
- MAPEX Center for Materials and Processes
| | - Andreas Rosenauer
- Institute of Solid State Physics
- University Bremen
- Bremen
- Germany
- MAPEX Center for Materials and Processes
| | - Thorsten M. Gesing
- Solid State Chemical Crystallography, Institute of Inorganic Chemistry and Crystallography/FB02
- University Bremen
- Bremen
- Germany
- MAPEX Center for Materials and Processes
| | - Marcus Bäumer
- Institute of Applied and Physical Chemistry and Center for Environmental Research and Sustainable Technology
- University Bremen
- Bremen
- Germany
- MAPEX Center for Materials and Processes
| | - Arne Wittstock
- Institute of Applied and Physical Chemistry and Center for Environmental Research and Sustainable Technology
- University Bremen
- Bremen
- Germany
- MAPEX Center for Materials and Processes
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25
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Tchoua Ngamou PH, El Kasmi A, Weiss T, Vieker H, Beyer A, Zielasek V, Kohse-Höinghaus K, Bäumer M. Investigation of the Growth Behaviour of Cobalt Thin Films from Chemical Vapour Deposition, Using Directly Coupled X-ray Photoelectron Spectroscopy. Z PHYS CHEM 2015. [DOI: 10.1515/zpch-2015-0602] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
Thin films and coatings are a basis for many technological processes,
including microelectronics, electrochemistry and catalysis. The
successful deposition of metal films and nanoparticles by chemical
vapour deposition (CVD) needs control over a number of
physico-chemical processes such as precursor and substrate selection,
delivery, temperature, pressure and flow conditions. Here, cobalt thin
films were deposited by means of pulsed-spray evaporation chemical
vapour deposition (PSE-CVD) from ethanol solutions of
Co(acac)2 and Co(acac)3 on bare glass and silicon
substrates. The physico-chemical properties of the grown films were
characterised by XRD (X-ray diffraction), XPS (X-ray photoelectron
spectroscopy) and HIM (helium ion microscopy). Co(acac)2
enabled the growth of cobalt metal at lower temperatures than
Co(acac)3. The difference in deposition temperature was
attributed to the ability of ethanol to reduce Co(acac)2
better than Co(acac)3. In addition, the film deposited from
Co(acac)2 exhibited a higher metal content and a less porous
structure than that deposited from Co(acac)3. Increasing the
substrate temperature enhanced the carbon content because of the
thermal decomposition of both precursors. Using a nickel seed layer
improved the growth rate until a critical temperature of
360 ℃, at which the thermal decomposition of the
precursor becomes predominant. A decrease in the deposition
temperature when using the nickel seed layer was only observed with
Co(acac)2 precursor; the growth behaviour under these
conditions was monitored with a unique UHV-compatible PSE-CVD reactor
directly attached to an XPS system and ascribed to an enhancement of
its catalytic reduction by ethanol.
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Affiliation(s)
| | | | - Theodor Weiss
- Institute of Applied and Physical Chemistry, University of Bremen, Leobener Straße UFT, D-28359 Bremen, Germany
| | | | - André Beyer
- Department of Physics, Bielefeld University, Universitätsstraße 25, D-33615 Bielefeld, Germany
| | - Volkmar Zielasek
- Institute of Applied and Physical Chemistry, University of Bremen, Leobener Straße UFT, D-28359 Bremen, Germany
| | | | - Marcus Bäumer
- Institute of Applied and Physical Chemistry, University of Bremen, Leobener Straße UFT, D-28359 Bremen, Germany
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26
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Kahl M, Gökçen A, Fischer S, Bäumer M, Wiesner J, Lochnit G, Wygrecka M, Vilcinskas A, Preissner KT. Maggot excretion products from the blowfly Lucilia sericata contain contact phase/intrinsic pathway-like proteases with procoagulant functions. Thromb Haemost 2015; 114:277-88. [PMID: 25948398 DOI: 10.1160/th14-06-0499] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Accepted: 03/15/2015] [Indexed: 01/09/2023]
Abstract
For centuries, maggots have been used for the treatment of wounds by a variety of ancient cultures, as part of their traditional medicine. With increasing appearance of antimicrobial resistance and in association with diabetic ulcers, maggot therapy was revisited in the 1980s. Three mechanisms by which sterile maggots of the green bottle fly Lucilia sericata may improve healing of chronic wounds have been proposed: Biosurgical debridement, disinfecting properties, and stimulation of the wound healing process. However, the influence of maggot excretion products (MEP) on blood coagulation as part of the wound healing process has not been studied in detail. Here, we demonstrate that specific MEP-derived serine proteases from Lucilia sericata induce clotting of human plasma and whole blood, particularly by activating contact phase proteins factor XII and kininogen as well as factor IX, thereby providing kallikrein-bypassing and factor XIa-like activities, both in plasma and in isolated systems. In plasma samples deficient in contact phase proteins, MEP restored full clotting activity, whereas in plasma deficient in either factor VII, IX, X or II no effect was seen. The observed procoagulant/intrinsic pathway-like activity was mediated by (chymo-) trypsin-like proteases in total MEP, which were significantly blocked by C1-esterase inhibitor or other contact phase-specific protease inhibitors. No significant influence of MEP on platelet activation or fibrinolysis was noted. Together, MEP provides contact phase bypassing procoagulant activity and thereby induces blood clotting in the context of wound healing. Further characterisation of the active serine protease(s) may offer new perspectives for biosurgical treatment of chronic wounds.
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Affiliation(s)
| | | | | | | | | | | | | | | | - K T Preissner
- Klaus T. Preissner, PhD, Department of Biochemistry, Medical School, Justus-Liebig-University, Friedrichstrasse 24, 35392 Giessen, Germany, Tel.: +49 641 994 7500, Fax: +49 641 994 7509, E-mail:
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27
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Niu G, Zoellner MH, Schroeder T, Schaefer A, Jhang JH, Zielasek V, Bäumer M, Wilkens H, Wollschläger J, Olbrich R, Lammers C, Reichling M. Controlling the physics and chemistry of binary and ternary praseodymium and cerium oxide systems. Phys Chem Chem Phys 2015; 17:24513-40. [DOI: 10.1039/c5cp02283e] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Binary and ternary PrOxand CeOxfilms grown on Si(111) are most versatile systems available in a variety of stoichiometries and surface structures.
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Affiliation(s)
- Gang Niu
- IHP
- 15236 Frankfurt(Oder)
- Germany
- BTU Cottbus-Senftenberg
- Institute of Physics
| | | | - Thomas Schroeder
- IHP
- 15236 Frankfurt(Oder)
- Germany
- BTU Cottbus-Senftenberg
- Institute of Physics
| | - Andreas Schaefer
- Institute of Applied and Physical Chemistry
- University of Bremen
- 28359 Bremen
- Germany
| | - Jin-Hao Jhang
- Institute of Applied and Physical Chemistry
- University of Bremen
- 28359 Bremen
- Germany
| | - Volkmar Zielasek
- Institute of Applied and Physical Chemistry
- University of Bremen
- 28359 Bremen
- Germany
| | - Marcus Bäumer
- Institute of Applied and Physical Chemistry
- University of Bremen
- 28359 Bremen
- Germany
| | - Henrik Wilkens
- Fachbereich Physik
- Universität Osnabrück
- 49076 Osnabrück
- Germany
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28
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Mueller R, Zhang S, Klink M, Bäumer M, Vasenkov S. The origin of a large apparent tortuosity factor for the Knudsen diffusion inside monoliths of a samaria–alumina aerogel catalyst: a diffusion NMR study. Phys Chem Chem Phys 2015; 17:27481-7. [DOI: 10.1039/c5cp04609b] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The contribution from surface diffusion into the apparent tortuosity factor can be separated for light gases in a porous catalyst.
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Affiliation(s)
- R. Mueller
- Department of Chemical Engineering
- University of Florida
- Gainesvlle
- USA
| | - S. Zhang
- Department of Chemical Engineering
- University of Florida
- Gainesvlle
- USA
| | - M. Klink
- Institute for Applied and Physical Chemistry
- University of Bremen
- Bremen
- Germany
| | - M. Bäumer
- Institute for Applied and Physical Chemistry
- University of Bremen
- Bremen
- Germany
| | - S. Vasenkov
- Department of Chemical Engineering
- University of Florida
- Gainesvlle
- USA
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29
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Altmann L, Wang X, Borchert H, Kolny-Olesiak J, Zielasek V, Parisi J, Kunz S, Bäumer M. Influence of Sn content on the hydrogenation of crotonaldehyde catalysed by colloidally prepared PtSn nanoparticles. Phys Chem Chem Phys 2015; 17:28186-92. [DOI: 10.1039/c5cp00280j] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
For increasing tin concentrations PtSn nanoparticles of similar size show a monotonically increasing selectivity towards crotylalcohol and a volcano like activity.
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Affiliation(s)
- Lena Altmann
- Institute of Applied and Physical Chemistry and Center for Environmental Research and Sustainable Technology
- University of Bremen Leobener Str. UFT
- D-28359 Bremen
- Germany
| | - Xiaodong Wang
- Technical Electrochemistry
- Faculty of Chemistry Technische Universität München
- D-85748 Garching
- Germany
| | - Holger Borchert
- Energy and Semiconductor Research Laboratory
- Department of Physics
- University of Oldenburg
- D-26129 Oldenburg
- Germany
| | - Joanna Kolny-Olesiak
- Energy and Semiconductor Research Laboratory
- Department of Physics
- University of Oldenburg
- D-26129 Oldenburg
- Germany
| | - Volkmar Zielasek
- Institute of Applied and Physical Chemistry and Center for Environmental Research and Sustainable Technology
- University of Bremen Leobener Str. UFT
- D-28359 Bremen
- Germany
| | - Jürgen Parisi
- Energy and Semiconductor Research Laboratory
- Department of Physics
- University of Oldenburg
- D-26129 Oldenburg
- Germany
| | - Sebastian Kunz
- Institute of Applied and Physical Chemistry and Center for Environmental Research and Sustainable Technology
- University of Bremen Leobener Str. UFT
- D-28359 Bremen
- Germany
| | - Marcus Bäumer
- Institute of Applied and Physical Chemistry and Center for Environmental Research and Sustainable Technology
- University of Bremen Leobener Str. UFT
- D-28359 Bremen
- Germany
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30
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Morsbach E, Nesselberger M, Warneke J, Harz P, Arenz M, Bäumer M, Kunz S. 1-Naphthylamine functionalized Pt nanoparticles: electrochemical activity and redox chemistry occurring on one surface. NEW J CHEM 2015. [DOI: 10.1039/c4nj02040e] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Platinum nanoparticles functionalized with oligomerized 1-naphthylamine form a material where the organic ligand exhibits electrochemical activity and the metal surface catalytic activity.
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Affiliation(s)
- Eva Morsbach
- IAPC (Institute of Applied and Physical Chemistry)
- University of Bremen
- D-28359 Bremen
- Germany
| | - Markus Nesselberger
- Nano-Science Center
- Department of Chemistry
- University of Copenhagen
- Universitetsparken 5
- 2100 Copenhagen
| | - Jonas Warneke
- IAPC (Institute of Applied and Physical Chemistry)
- University of Bremen
- D-28359 Bremen
- Germany
| | - Philipp Harz
- IAPC (Institute of Applied and Physical Chemistry)
- University of Bremen
- D-28359 Bremen
- Germany
| | - Matthias Arenz
- Nano-Science Center
- Department of Chemistry
- University of Copenhagen
- Universitetsparken 5
- 2100 Copenhagen
| | - Marcus Bäumer
- IAPC (Institute of Applied and Physical Chemistry)
- University of Bremen
- D-28359 Bremen
- Germany
| | - Sebastian Kunz
- IAPC (Institute of Applied and Physical Chemistry)
- University of Bremen
- D-28359 Bremen
- Germany
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31
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Wichmann A, Bäumer M, Wittstock A. Oxidative Coupling of Alcohols and Amines over Bimetallic Unsupported Nanoporous Gold: Tailored Activity through Mechanistic Predictability. ChemCatChem 2014. [DOI: 10.1002/cctc.201402843] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Weiss T, Nowak M, Mundloch U, Zielasek V, Kohse-Höinghaus K, Bäumer M. Design of a compact ultrahigh vacuum-compatible setup for the analysis of chemical vapor deposition processes. Rev Sci Instrum 2014; 85:104104. [PMID: 25362422 DOI: 10.1063/1.4897620] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Optimizing thin film deposition techniques requires contamination-free transfer from the reactor into an ultrahigh vacuum (UHV) chamber for surface science analysis. A very compact, multifunctional Chemical Vapor Deposition (CVD) reactor for direct attachment to any typical UHV system for thin film analysis was designed and built. Besides compactness, fast, easy, and at the same time ultimately clean sample transfer between reactor and UHV was a major goal. It was achieved by a combination of sample manipulation parts, sample heater, and a shutter mechanism designed to fit all into a NW38 Conflat six-ways cross. The present reactor design is versatile to be employed for all commonly employed variants of CVD, including Atomic Layer Deposition. A demonstration of the functionality of the system is provided. First results of the setup (attached to an Omicron Multiprobe x-ray photoelectron spectroscopy system) on the temperature dependence of Pulsed Spray Evaporation-CVD of Ni films from Ni acetylacetonate as the precursor demonstrate the reactor performance and illustrate the importance of clean sample transfer without breaking vacuum in order to obtain unambiguous results on the quality of CVD-grown thin Ni films. The widely applicable design holds promise for future systematic studies of the fundamental processes during chemical vapor deposition or atomic layer deposition.
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Affiliation(s)
- Theodor Weiss
- Institut für Angewandte und Physikalische Chemie, Universität Bremen, Leobener Straße UFT, D-28359 Bremen, Germany
| | - Martin Nowak
- Institut für Angewandte und Physikalische Chemie, Universität Bremen, Leobener Straße UFT, D-28359 Bremen, Germany
| | - Udo Mundloch
- Physikalische Chemie I, Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, D-33615 Bielefeld, Germany
| | - Volkmar Zielasek
- Institut für Angewandte und Physikalische Chemie, Universität Bremen, Leobener Straße UFT, D-28359 Bremen, Germany
| | - Katharina Kohse-Höinghaus
- Physikalische Chemie I, Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, D-33615 Bielefeld, Germany
| | - Marcus Bäumer
- Institut für Angewandte und Physikalische Chemie, Universität Bremen, Leobener Straße UFT, D-28359 Bremen, Germany
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33
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Wichmann A, Schnurpfeil G, Backenköhler J, Kolke L, Azov VA, Wöhrle D, Bäumer M, Wittstock A. A versatile synthetic strategy for nanoporous gold–organic hybrid materials for electrochemistry and photocatalysis. Tetrahedron 2014. [DOI: 10.1016/j.tet.2014.03.091] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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34
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Morsbach E, Brauns E, Kowalik T, Lang W, Kunz S, Bäumer M. Ligand-stabilized Pt nanoparticles (NPs) as novel materials for catalytic gas sensing: influence of the ligand on important catalytic properties. Phys Chem Chem Phys 2014; 16:21243-51. [DOI: 10.1039/c4cp02993c] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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35
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Morsbach E, Spéder J, Arenz M, Brauns E, Lang W, Kunz S, Bäumer M. Stabilizing catalytically active nanoparticles by ligand linking: toward three-dimensional networks with high catalytic surface area. Langmuir 2014; 30:5564-73. [PMID: 24761778 DOI: 10.1021/la4049055] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A general approach for the linking of Pt nanoparticles (NPs) with bifunctional amine ligands (organic molecules with two amine groups) is presented that allows for the preparation of NP catalysts without inorganic supports and high densities of the catalytically active metal. Advantage was taken of the use of "unprotected" NPs, which enables us to prepare different ligand-functionalized NPs from the same particle batch and thus to relate changes of the resulting material properties exclusively to the influence of the ligand. Three bifunctional ligands with similar functional groups (amines) but different hydrocarbon skeletons were used and compared to monofunctional ligands of similar molecular structures (alkyl and aryl amines) showing significantly different material properties. Monofunctional molecules with minor steric demand cover almost completely the NP surface and lead to two-dimensional assembling of the NPs. In contrast, the use of bifunctional amine ligands leads to the formation of porous, three-dimensional NP networks (ligand-linked NPs) with a high density of ligand free surface atoms, thus enabling for the application as catalytic materials. The stabilizing effect of bifunctional ligands serves as an alternative to the use of inorganic support materials and enables for catalytic applications of ligand-linked NP networks.
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Affiliation(s)
- Eva Morsbach
- IAPC (Institute of Applied and Physical Chemistry), University of Bremen , Leobener Str. NW2, 28359 Bremen, Germany
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36
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Elkins TW, Neumann B, Bäumer M, Hagelin-Weaver HE. Effects of Li Doping on MgO-Supported Sm2O3 and TbOx Catalysts in the Oxidative Coupling of Methane. ACS Catal 2014. [DOI: 10.1021/cs500138j] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Trenton W. Elkins
- Department
of Chemical Engineering, University of Florida, Gainesville, Florida 32611, United States
| | - Björn Neumann
- Institute of Applied and Physical Chemistry & Center for Environmental Research and Sustainable Technology, University Bremen, Leobener Strasse UFT, 28359 Bremen, Germany
| | - Marcus Bäumer
- Institute of Applied and Physical Chemistry & Center for Environmental Research and Sustainable Technology, University Bremen, Leobener Strasse UFT, 28359 Bremen, Germany
| | - Helena E. Hagelin-Weaver
- Department
of Chemical Engineering, University of Florida, Gainesville, Florida 32611, United States
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Neumann B, Gesing TM, Rednyk A, Matolin V, Gash AE, Bäumer M. Sol-gel preparation of alumina stabilized rare earth areo- and xerogels and their use as oxidation catalysts. J Colloid Interface Sci 2014; 422:71-8. [PMID: 24655831 DOI: 10.1016/j.jcis.2014.02.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Revised: 02/01/2014] [Accepted: 02/05/2014] [Indexed: 11/18/2022]
Abstract
A new sol-gel synthesis route for rare earth (Ce and Pr) alumina hybrid aero- and xerogels is presented which is based on the so-called epoxide addition method. The resulting materials are characterized by TEM, XRD and nitrogen adsorption. The results reveal a different crystallization behavior for the praseodymia/alumina and the ceria/alumina gel. Whereas the first remains amorphous until 875°C, small ceria domains form already after preparation in the second case which grow with increasing calcination temperature. The use of the calcined gels as CO oxidation catalysts was studied in a quartz tube (lab) reactor and in a (slit) microreactor and compared to reference catalysts consisting of the pure rare earth oxides. The Ce/Al hybrid gels exhibit a good catalytic activity and a thermal stability against sintering which was superior to the investigated reference catalyst. In contrast, the Pr/Al hybrid gels show lower CO oxidation activity which, due to the formation of PrAlO3, decreased with increasing calcination temperature.
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Affiliation(s)
- Björn Neumann
- Institute of Applied and Physical Chemistry & Center for Environmental Research and Sustainable Technology, University of Bremen, Leobener Str., Bremen D-28359, Germany
| | - Thorsten M Gesing
- Solid State Chemical Crystallography, Institute for Inorganic Chemistry, University of Bremen, Leobener Str. NW2, D-28359 Bremen, Germany
| | - Andrii Rednyk
- Charles University, Faculty of Mathematics and Physics, Department of Surface and Plasma Science, V Holešovičkách 2, 18000 Prague 8, Czech Republic
| | - Vladimir Matolin
- Charles University, Faculty of Mathematics and Physics, Department of Surface and Plasma Science, V Holešovičkách 2, 18000 Prague 8, Czech Republic
| | - Alexander E Gash
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94551, USA.
| | - Marcus Bäumer
- Institute of Applied and Physical Chemistry & Center for Environmental Research and Sustainable Technology, University of Bremen, Leobener Str., Bremen D-28359, Germany.
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38
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Abstract
Catalysis is one of the key technologies for the 21st century for achieving the required sustainability of chemical processes. Critical improvements are based on the development of new catalysts and catalytic concepts. In this context, gold holds great promise because it is more active and selective than other precious metal catalysts at low temperatures. However, gold becomes only chemically and catalytically active when it is nanostructured. Since the 1970s and 1980s, the first type of gold catalysts that chemists studied were small nanoparticles on oxidic supports. With the later onset of nanotechnology, a variety of nanostructured materials not requiring a support or organic stabilizers became available within about the last 10 years. Among these are gold nanofoams generated by combustion of gold compounds, nanotube membranes prepared by electroless deposition of gold inside a template, and corrosion-derived nanoporous gold. Even though these materials are macroscopic in their geometric dimensions (e.g., disks, cubes, and membranes with dimensions of millimeters), they are comprised of gold nanostructures, for example, in the form of ligaments as small as 15 nm in diameter (nanoporous gold, npAu). The nanostructure brings about a high surface to volume ratio and a large fraction of low coordinated surface atoms. In this Account, we discuss how unsupported materials are active catalysts for aerobic oxidation reaction in gas phase (oxidation of CO and primary alcohols), as well as liquid phase oxidation and reduction reactions. It turns out that the bonding and activation of molecular oxygen for gas phase oxidations strongly profits from trace amounts of an ad-metal residue such as silver. It is noteworthy that these catalysts still exhibit the special gold type chemistry, characterized by activity at very low temperatures and high selectivity for partial oxidations. For example, we can oxidize CO over these unsupported catalysts (npAu, nanotubes, and powder) at temperatures well below water's freezing point (-30 °C) and with turnover frequencies up to 0.5 s(-1) (at 30 °C). Yet, we can anticipate the surface chemistry of these unsupported and extended gold surfaces based on model experiments under UHV conditions. We have demonstrated this for the selective oxidation of primary alcohols at low temperatures employing npAu catalysts. Chemists have paid growing interest to oxidation and reduction reactions in liquid phase catalysis, most suitable for synthetic organic chemistry. Early work on the aerobic oxidation of d-glucose in 2008 using Raney type npAu already showed the potential of this type of catalyst for liquid phase reactions. Since then, researchers have investigated further oxidation reactions (silanes to silanols) and reduction reactions of alkynes, as well as C-C coupling reactions ([4 + 2] benzannulation) and azo compound decomposition, with likely several more reactions to be reported in the next years. The advantage of this unsupported skeletal type of catalyst is its recyclability and retrievability without leaching of gold into the reaction medium, owing to its monolithic structure. Even though these materials contain nanoscopic structures, they are macroscopic in their geometric dimensions and pose no threat to the environment or health as discussed for other nanomaterials.
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Affiliation(s)
- Arne Wittstock
- Institute for Applied and Physical Chemistry and Center for Environmental Research and Sustainable Technology, University of Bremen, 28359 Bremen, Germany
| | - Marcus Bäumer
- Institute for Applied and Physical Chemistry and Center for Environmental Research and Sustainable Technology, University of Bremen, 28359 Bremen, Germany
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Bäumer M, Libuda J, Sandell A, Freund HJ, Graw G, Bertrams T, Neddermeyer H. The Growth and Properties of Pd and Pt on Al2O3/NiAl(110). ACTA ACUST UNITED AC 2014. [DOI: 10.1002/bbpc.199500089] [Citation(s) in RCA: 81] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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40
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Arndt D, Zielasek V, Dreher W, Bäumer M. Ethylene diamine-assisted synthesis of iron oxide nanoparticles in high-boiling polyolys. J Colloid Interface Sci 2014; 417:188-98. [DOI: 10.1016/j.jcis.2013.11.023] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2013] [Revised: 10/31/2013] [Accepted: 11/11/2013] [Indexed: 11/28/2022]
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41
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Speder J, Altmann L, Bäumer M, Kirkensgaard JJK, Mortensen K, Arenz M. The particle proximity effect: from model to high surface area fuel cell catalysts. RSC Adv 2014. [DOI: 10.1039/c4ra00261j] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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42
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Wilkens H, Schuckmann O, Oelke R, Gevers S, Reichling M, Schaefer A, Bäumer M, Zoellner MH, Niu G, Schroeder T, Wollschläger J. Structural transitions of epitaxial ceria films on Si(111). Phys Chem Chem Phys 2013; 15:18589-18599. [PMID: 24076746 DOI: 10.1063/1.4795867] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The structural changes of a (111) oriented CeO2 film grown on a Si(111) substrate covered with a hex-Pr2O3(0001) interface layer due to post deposition annealing are investigated. X-ray photoelectron spectroscopy measurements revealing the near surface stoichiometry show that the film reduces continuously upon extended heat treatment. The film is not homogeneously reduced since several coexisting crystalline ceria phases are stabilized due to subsequent annealing at different temperatures as revealed by high resolution low energy electron diffraction and X-ray diffraction. The electron diffraction measurements show that after annealing at 660 °C the ι-phase (Ce7O12) is formed at the surface which exhibits a (√7 × √7)R19.1° structure. Furthermore, a (√27 × √27)R30° surface structure with a stoichiometry close to Ce2O3 is stabilized after annealing at 860 °C which cannot be attributed to any bulk phase of ceria stable at room temperature. In addition, it is shown that the fully reduced ceria (Ce2O3) film exhibits a bixbyite structure. Polycrystalline silicate (CeSi(x)O(y)) and crystalline silicide (CeSi1.67) are formed at 850 °C and detected at the surface after annealing above 900 °C.
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Affiliation(s)
- H Wilkens
- Fachbereich Physik, Universität Osnabrück, Barbarastr. 7, 49076 Osnabrück, Germany.
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Mueller R, Zhang S, Neumann B, Bäumer M, Vasenkov S. Self-diffusion of carbon dioxide in samaria/alumina aerogel catalyst using high field NMR diffusometry. J Chem Phys 2013; 139:154703. [PMID: 24160529 DOI: 10.1063/1.4824635] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Pulsed field gradient (PFG) NMR was used to investigate the self-diffusion of carbon dioxide in alumina stabilized samaria aerogel catalyst, a promising porous catalyst for gas-phase reactions featuring high porosity and high surface area. For diffusion studies, the catalyst was prepared in two sample packing types, macroscopic monoliths (i.e., macroscopic cylindrical particles) and powder beds with particle sizes around 200 μm that are considered for catalytic applications. Studies of diffusion in these samples revealed how macroscopic packing influences the catalyst transport properties. Application of a high magnetic field of 17.6 T in the reported PFG NMR studies enabled diffusion measurements for relatively low carbon dioxide densities in the catalyst samples corresponding to a gas loading pressure of around 0.1 atm. As a result, it was possible to perform diffusion measurements for a large range of carbon dioxide loading pressures between 0.1 and 10 atm. The measured carbon dioxide diffusivities in the beds of catalyst particles are interpreted in the context of a simple diffusion-mediated exchange model previously used for zeolites and other porous materials.
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Affiliation(s)
- Robert Mueller
- Department of Chemical Engineering, University of Florida, Gainesville, Florida 32611 USA
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Müller R, Zhang S, Neumann B, Bäumer M, Vasenkov S. Study of Carbon Dioxide Transport in a Samaria Aerogel Catalyst by High Field Diffusion NMR. CHEM-ING-TECH 2013. [DOI: 10.1002/cite.201300041] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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45
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Altmann L, Wang X, Stöver J, Klink M, Zielasek V, Thiel K, Kolny-Olesiak J, Al-Shamery K, Borchert H, Parisi J, Bäumer M. Impact of Organic Ligands on the Structure and Hydrogenation Performance of Colloidally Prepared Bimetallic PtSn Nanoparticles. ChemCatChem 2013. [DOI: 10.1002/cctc.201200849] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Menezes WG, Neumann B, Zielasek V, Thiel K, Bäumer M. Bimetallic AuAg Nanoparticles: Enhancing the Catalytic Activity of Au for Reduction Reactions in the Liquid Phase by Addition of Ag. Chemphyschem 2013; 14:1577-81. [DOI: 10.1002/cphc.201201100] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2012] [Revised: 03/02/2013] [Indexed: 11/11/2022]
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47
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Menezes W, Altmann L, Zielasek V, Thiel K, Bäumer M. Bimetallic Co–Pd catalysts: Study of preparation methods and their influence on the selective hydrogenation of acetylene. J Catal 2013. [DOI: 10.1016/j.jcat.2012.12.023] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Wichmann A, Wittstock A, Frank K, Biener MM, Neumann B, Mädler L, Biener J, Rosenauer A, Bäumer M. Maximizing Activity and Stability by Turning Gold Catalysis Upside Down: Oxide Particles on Nanoporous Gold. ChemCatChem 2013. [DOI: 10.1002/cctc.201200759] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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49
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Menezes W, Zielasek V, Thiel K, Hartwig A, Bäumer M. Effects of particle size, composition, and support on catalytic activity of AuAg nanoparticles prepared in reverse block copolymer micelles as nanoreactors. J Catal 2013. [DOI: 10.1016/j.jcat.2012.12.006] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Filser J, Arndt D, Baumann J, Geppert M, Hackmann S, Luther EM, Pade C, Prenzel K, Wigger H, Arning J, Hohnholt MC, Köser J, Kück A, Lesnikov E, Neumann J, Schütrumpf S, Warrelmann J, Bäumer M, Dringen R, von Gleich A, Swiderek P, Thöming J. Intrinsically green iron oxide nanoparticles? From synthesis via (eco-)toxicology to scenario modelling. Nanoscale 2013; 5:1034-1046. [PMID: 23255050 DOI: 10.1039/c2nr31652h] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Iron oxide nanoparticles (IONP) are currently being studied as green magnet resonance imaging (MRI) contrast agents. They are also used in huge quantities for environmental remediation and water treatment purposes, although very little is known on the consequences of such applications for organisms and ecosystems. In order to address these questions, we synthesised polyvinylpyrrolidone-coated IONP, characterised the particle dispersion in various media and investigated the consequences of an IONP exposure using an array of biochemical and biological assays. Several theoretical approaches complemented the measurements. In aqueous dispersion IONP had an average hydrodynamic diameter of 25 nm and were stable over six days in most test media, which could also be predicted by stability modelling. The particles were tested in concentrations of up to 100 mg Fe per L. The activity of the enzymes glutathione reductase and acetylcholine esterase was not affected, nor were proliferation, morphology or vitality of mammalian OLN-93 cells although exposure of the cells to 100 mg Fe per L increased the cellular iron content substantially. Only at this concentration, acute toxicity tests with the freshwater flea Daphnia magna revealed slightly, yet insignificantly increased mortality. Two fundamentally different bacterial assays, anaerobic activated sludge bacteria inhibition and a modified sediment contact test with Arthrobacter globiformis, both rendered results contrary to the other assays: at the lowest test concentration (1 mg Fe per L), IONP caused a pronounced inhibition whereas higher concentrations were not effective or even stimulating. Preliminary and prospective risk assessment was exemplified by comparing the application of IONP with gadolinium-based nanoparticles as MRI contrast agents. Predicted environmental concentrations were modelled in two different scenarios, showing that IONP could reduce the environmental exposure of toxic Gd-based particles by more than 50%. Application of the Swiss "Precautionary Matrix for Synthetic Nanomaterials" rendered a low precautionary need for using our IONP as MRI agents and a higher one when using them for remediation or water treatment. Since IONP and (considerably more reactive) zerovalent iron nanoparticles are being used in huge quantities for environmental remediation purposes, it has to be ascertained that these particles pose no risk to either human health or to the environment.
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