Search

Your search keyword '"Michael Haevecker"' showing total 4 results
Start Over Author "Michael Haevecker" Topic chemistry.chemical_element
4 results on '"Michael Haevecker"'

1. Improving the Catalytic Performance of Cobalt for CO Preferential Oxidation by Stabilizing the Active Phase through Vanadium Promotion

Author

Spyridon Zafeiratos, Walid Baaziz, Michael Haevecker, Detre Teschner, Mathias Barreau, Luca Braglia, Liping Zhong, Elisa Borfecchia, Vasiliki Papaefthimiou, Valérie Caps, Institut de chimie et procédés pour l'énergie, l'environnement et la santé (ICPEES), Université de Strasbourg (UNISTRA)-Matériaux et nanosciences d'Alsace (FMNGE), Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Max-Planck-Institut für Chemische Energiekonversion (MPI-CEC), Max-Planck-Gesellschaft, Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique, Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA), Università degli studi di Torino (UNITO), Laboratorio TASC (IOM CNR), Consiglio Nazionale delle Ricerche (CNR), Université de Strasbourg (UNISTRA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Matériaux et Nanosciences Grand-Est (MNGE), Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Matériaux et Nanosciences Grand-Est (MNGE), Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique, Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), Università degli studi di Torino = University of Turin (UNITO), and CAPS, Valérie

Subjects
NAP-XPS, Trace Amounts, Inorganic chemistry, chemistry.chemical_element, Vanadium, COPrOx, operando spectroscopy, 010402 general chemistry, 01 natural sciences, Catalysis, NEXAFS, Operando spectroscopy, Active phase, [CHIM] Chemical Sciences, [CHIM]Chemical Sciences, Metal catalyst, vanadium oxides, cobalt oxides, mixed oxides, 010405 organic chemistry, Chemistry, [CHIM.CATA]Chemical Sciences/Catalysis, General Chemistry, XANES, 0104 chemical sciences, Chimie/Catalyse, Cobalt
Abstract

Preferential oxidation of CO (COPrOx) is a catalytic reaction targeting the removal of trace amounts of CO from hydrogen-rich gas mixtures. Non-noble metal catalysts, such as Cu and Co, can be equally active to Pt for the reaction; however, their commercialization is limited by their poor stability. We have recently shown that CoO is the most active state of cobalt for COPrOx, but under certain reaction conditions, it is readily oxidized to Co3O4 and deactivates. Here, we report a simple method to stabilize the Co2+ state by vanadium addition. The V-promoted cobalt catalyst exhibits considerably higher activity and stability than pure cobalt. The nature of the catalytic active sites during COPrOx was established by operando NAP-XPS and NEXAFS, while the stability of the Co2+ state on the surface was verified by in situ NEXAFS at 1 bar pressure. The active phase consists of an ultra-thin cobalt-vanadate surface layer, containing tetrahedral V5+ and octahedral Co2+ cations, with an electronic and geometric structure that is deviating from the standard mixed bulk oxides. In addition, V addition helps to maintain the population of Co2+ species involved in the reaction, inhibiting carbonate species formation that are responsible for the deactivation. The promoting effect of V is discussed in terms of enhancement of CoO redox stability on the surface induced by electronic and structural modifications. These results demonstrate that V-promoted cobalt is a promising COPrOx catalyst and validate the application of in situ spectroscopy to provide the concept for designing better performing catalysts.

Published
2021
Full Text
View/download PDF

2. Effect of manganese promotion on the activity and selectivity of cobalt catalysts for CO preferential oxidation

Author

Spyridon Zafeiratos, David Horst Simonne, Walid Baaziz, Michael Haevecker, Mathias Barreau, Dingkai Chen, Valérie Caps, Břetislav Šmíd, Liping Zhong, Detre Teschner, Elisa Borfecchia, Institut de chimie et procédés pour l'énergie, l'environnement et la santé (ICPEES), Université de Strasbourg (UNISTRA)-Matériaux et nanosciences d'Alsace (FMNGE), Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Fritz-Haber-Institut der Max-Planck-Gesellschaft (FHI), Max Planck Society, Università degli studi di Torino (UNITO), Charles University [Prague] (CU), Université de Strasbourg (UNISTRA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Matériaux et Nanosciences Grand-Est (MNGE), Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Università degli studi di Torino = University of Turin (UNITO), and univOAK, Archive ouverte

Subjects
inorganic chemicals, NAP-XPS, chemistry.chemical_element, Context (language use), 02 engineering and technology, Manganese, Operando spectroscopy, COPrOx, 010402 general chemistry, 01 natural sciences, Hydrogen purifier, Catalysis, Mixed oxides, NEXAFS, Transition metal, Methanation, Reactivity (chemistry), Selectivity, General Environmental Science, Cobalt oxides, Manganese oxides, Process Chemistry and Technology, [CHIM.CATA] Chemical Sciences/Catalysis, [CHIM.CATA]Chemical Sciences/Catalysis, 021001 nanoscience & nanotechnology, 0104 chemical sciences, chemistry, Chemical engineering, 0210 nano-technology, Cobalt, Chimie/Catalyse
Abstract

The preferential oxidation of CO in H2-rich mixtures (COPrOx) is a major catalytic reaction utilized for hydrogen purification. In the exploration of alternatives to noble metals, cobalt-based catalysts appear to be a very promising choice. The activity and stability of cobalt in the COPrOx reaction can be improved by the addition of transition metals and manganese is maybe the most prominent among them. Yet, the arrangement of the two components in the catalytically active state is largely unknown, which hinders in-depth understanding of the manganese promotion effect. Here, we compare pure and Mn-modified cobalt catalysts and correlate their structural and chemical characteristics with their COPrOx performance. The Mn-promoted cobalt catalyst is significantly more active than pure cobalt especially at intermediate reaction temperatures (around 200 °C). The addition of Mn improves the structural stability of the catalyst and helps to maintain higher specific surface areas. Chemical and microstructural analysis using various operando and in situ techniques revealed that Mn promotes CO conversion by partially stabilizing CoO phase during reaction conditions. It is also suggested that at high temperature, Mn suppress CO methanation reaction but promotes H2 oxidation. Apart of the particular interest in COPrOx reaction, in a general context, this work shows how the spatial distribution of the different catalyst components at nanoscopic level, may affect the surface chemistry and consequently control the reactivity.

Published
2021
Full Text
View/download PDF

3. Operando observation of nickel/ceria electrode surfaces during intermediate temperature steam electrolysis

Author

Fotios Paloukis, Michael Haevecker, Dimitris K. Niakolas, Vasiliki Papaefthimiou, Axel Knop-Gericke, Spyridon Zafeiratos, and Detre Teschner

Subjects
Electrolysis, Hydrogen, Electrolytic cell, Inorganic chemistry, Oxide, chemistry.chemical_element, 02 engineering and technology, 010402 general chemistry, 021001 nanoscience & nanotechnology, Electrocatalyst, 7. Clean energy, 01 natural sciences, Catalysis, Cathode, 0104 chemical sciences, law.invention, Nickel, chemistry.chemical_compound, chemistry, Chemical engineering, law, High-temperature electrolysis, Physical and Theoretical Chemistry, 0210 nano-technology
Abstract

The solid oxide electrolysis cell (SOEC) technology has a huge potential for future mass production of hydrogen, mainly due to its high electrical-to-chemical energy conversion efficiency. However, the durability and the performance of SOEC devices are inferior to that of other competitive electrolysis technologies inhibiting the commercialization of SOECs. Despite the fact that Ni-based cermets are currently the most widely used cathode materials for SOEC, change of the nickel oxidation state has been accused as a major issue limiting the performance of these devices. In this work we provide operando experimental evidence of the active surface oxidation state and composition of nickel/doped-ceria cermets under water electrolysis conditions using ambient pressure X-ray photoelectron and near edge X-ray absorption fine structure spectroscopies, combined with quantitative spectra simulation. Remarkably under specific operational conditions, nickel is maintained in a partially oxidized state which, counterintuitive to the expected behavior, can be beneficial to the cell performance. This finding may initiate new improvement strategies for SOEC electrodes based on thorough optimization of the operational conditions, in order to engineer in situ the most propitious electrode configuration.

Published
2017
Full Text
View/download PDF

4. The catalytic properties of thin film Pd-rich GaPd2 in methanol steam reforming

Author

Raul Cardoso, Michael Haevecker, Bernhard Klötzer, Lukas Mayr, Simon Penner, Axel Knop-Gericke, Harald Lorenz, Raoul Blume, Yuan Luo, Ulrich Burkhardt, Sebastián Alarcón Villaseca, Dmitry Zemlyanov, and Marc Armbrüster

Subjects
IN-SITU XPS, Inorganic chemistry, Intermetallic, chemistry.chemical_element, PART, Catalysis, Steam reforming, chemistry.chemical_compound, Dehydrogenation, HYDROGENATION, Thin film, Physical and Theoretical Chemistry, Methanol steam reforming, Oxidative steam reforming, CONSEQUENCES, Chemistry, PALLADIUM, Nanoscience and Nanotechnology, SELECTIVITY, GALLIUM, In situ XPS, Intermetallic compounds, RAY PHOTOELECTRON-SPECTROSCOPY, Methanol, PD/GA2O3, Stoichiometry, Palladium, GaPd2
Abstract

An unsupported Pd-rich GaPd2 sample in form of a thin film has been prepared by alternating layer deposition of Pd and Ga metal and was subsequently used as a structurally and chemically stable model system to clarify the catalytic properties of the unsupported intermetallic compound GaPd2 in methanol steam reforming (MSR). The sample revealed a slightly Pd-richer GaPd2 bulk composition of Ga28Pd72, as evidenced by EDX analysis, low-energy ion scattering, X-ray diffraction measurements, and depth profiling by in situ X-ray photoelectron spectroscopy. The latter additionally showed a high stability of GaPd2 both under methanol and oxidative methanol steam reforming conditions. No active redox chemistry of Ga species or other reaction-induced oxidative Ga surface segregation has been detected during catalytic MSR reaction. Corroborating these observations, corresponding catalytic experiments under methanol steam reforming conditions revealed only a, in comparison with elemental Pd, very small activity in methanol dehydrogenation (CO formation rate at maximum 0.019 mbar min-1 ; 0.08 site-1 s-1 ). Unsupported thin film Pd-rich GaPd2 with the given surface and bulk stoichiometry must therefore be considered a poor methanol steam reforming/dehydrogenation catalyst. In oxidative steam reforming experiments, only total oxidation without significant H2 formation has been observed.

Published
2014

Catalog

Books, media, physical & digital resources
See catalog results