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Shun K, Mori K, Kidawara T, Ichikawa S, Yamashita H. Heteroatom doping enables hydrogen spillover via H +/e - diffusion pathways on a non-reducible metal oxide. Nat Commun 2024; 15:6403. [PMID: 39085195 PMCID: PMC11291974 DOI: 10.1038/s41467-024-50217-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2024] [Accepted: 07/01/2024] [Indexed: 08/02/2024] Open
Abstract
Hydrogen spillover, the simultaneous diffusion of protons (H+) and electrons (e-) is considered to be applicable to ubiquitous technologies related to hydrogen but limited to over reducible metal oxides. The present work demonstrates that a non-reducible MgO with heteroatom Al dopants (Al-MgO) allows hydrogen spillover in the same way as reducible metal oxides. Furthermore, a H+ storage capacity of this material owing to hydrogen spillover is more than three times greater than those of various standard metal oxides based on H+ transport channels within its bulk region. Atomic hydrogen diffuses over the non-reducible Al-MgO produces active H+-e- pairs, as also occurs on reducible metal oxides, to enhance the catalytic performance of Ni during CO2 hydrogenation. The H+ and e- diffusion pathways generated by the heteroatom Al doping are disentangled based on systematic characterizations and calculations. This work provides a new strategy for designing functional materials intended to hydrogen spillover for diverse applications in a future hydrogen-based society.
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Affiliation(s)
- Kazuki Shun
- Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka, Japan
| | - Kohsuke Mori
- Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka, Japan.
- Innovative Catalysis Science Division, Institute for Open and Transdisciplinary Research Initiatives (ICS-OTRI), Osaka University, Suita, Osaka, Japan.
| | - Takumi Kidawara
- Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka, Japan
| | - Satoshi Ichikawa
- Research Center for Ultra-High Voltage Electron Microscopy, Osaka University, Ibaraki, Japan
| | - Hiromi Yamashita
- Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka, Japan
- Innovative Catalysis Science Division, Institute for Open and Transdisciplinary Research Initiatives (ICS-OTRI), Osaka University, Suita, Osaka, Japan
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2
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Li H, Zhou S, Liu J, Wang W, Chen A, Sheng L, Zhao J, Li Y, Sui Y, Zou B. Construction of H-Doped PdB Nanocrystals as Electrocatalysts to Modulate Formic Acid Oxidation. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024:e2403813. [PMID: 38981017 DOI: 10.1002/advs.202403813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2024] [Revised: 06/24/2024] [Indexed: 07/11/2024]
Abstract
The strong ligand effect in B-doped Pd-based (PdB) catalysts renders them a promising anode for constructing formic acid fuel cells (FAFCs) exhibiting high power density and outstanding stability. However, the enhancement of the oxidation barrier is unavoidable in this alloy system owing to the electron transfer (ET) from B to Pd. In this study, a hydrogen doping strategy is employed to open charge freedom in PdB compounds and boost their formic acid oxidation reaction (FAOR) activity by suppressing the ET process. The resulting hydrogen-doped PdB (PdBH) exhibits an ultrahigh mass activity of up to 1.2A mg-1 Pd, which is 3.23 times that of the PdB catalyst and 9.55 times that of Pd black. Detailed experimental and theoretical studies show that the interstitial hydrogen leads to enhanced orbital hybridization and reduced electron density around Pd. This optimized ligand effect weakens the carbon monoxide adsorption and increases the direct pathway preference of PdBH, resulting in its outstanding catalytic activity for the FAOR. The development of this high-performance hydrogen-doped PdB catalyst is an important step toward the construction of advanced light element co-doped metal catalysts.
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Affiliation(s)
- Huiling Li
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, 2699 Qianjin Street, Changchun, 130012, China
| | - Shangqi Zhou
- Key Laboratory of Photonic and Electronic Bandgap Materials of MOE, College of Chemistry and Chemical Engineering, Harbin Normal University, Harbin, 150025, P. R. China
| | - Jiewen Liu
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, 2699 Qianjin Street, Changchun, 130012, China
| | - Weibin Wang
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, 2699 Qianjin Street, Changchun, 130012, China
| | - Ankang Chen
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, 2699 Qianjin Street, Changchun, 130012, China
| | - LiBo Sheng
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, 2699 Qianjin Street, Changchun, 130012, China
| | - Jingxiang Zhao
- Key Laboratory of Photonic and Electronic Bandgap Materials of MOE, College of Chemistry and Chemical Engineering, Harbin Normal University, Harbin, 150025, P. R. China
| | - Yan Li
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, 2699 Qianjin Street, Changchun, 130012, China
| | - Yongming Sui
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, 2699 Qianjin Street, Changchun, 130012, China
| | - Bo Zou
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, 2699 Qianjin Street, Changchun, 130012, China
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3
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Gloystein A, Soltanmohammadi M, Nilius N. Light Emission from Single Oxygen Vacancies in Cu 2O Films Probed with Scanning Tunneling Microscopy. J Phys Chem Lett 2023; 14:3980-3985. [PMID: 37083296 PMCID: PMC10165647 DOI: 10.1021/acs.jpclett.3c00642] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Global photoluminescence (PL) and spatially resolved scanning tunneling microscopy (STM) luminescence are compared for thick Cu2O films grown on Au(111). While the PL data reveal two peaks at 750 and 850 nm, assigned to radiative electron decays via localized gap states induced by O vacancies, a wide-band emission between 700 and 950 nm is observed in STM luminescence. The latter is compatible with cavity plasmons stimulated by inelastic electron tunneling and contains no spectral signature of the Cu2O defects. The STM luminescence is nonetheless controlled by O vacancies that provide inelastic excitation channels for the cavity plasmons. In fact, the emission yield sharply peaks at 2.2 V sample bias, when tip electrons are resonantly injected into O defect states and recombine with holes at the valence-band top via plasmon stimulation. The spatially confined emission centers detected in photon maps of the Cu2O films are therefore assigned to excitation channels mediated by single or few O vacancies in the oxide matrix.
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Affiliation(s)
- Alexander Gloystein
- Carl-von-Ossietzky University, Institute of Physics, D-26111 Oldenburg, Germany
| | | | - Niklas Nilius
- Carl-von-Ossietzky University, Institute of Physics, D-26111 Oldenburg, Germany
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4
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Abstract
The field of single-atom catalysis (SAC) has expanded greatly in recent years. While there has been much success developing new synthesis methods, a fundamental disconnect exists between most experiments and the theoretical computations used to model them. The real catalysts are based on powder supports, which inevitably contain a multitude of different facets, different surface sites, defects, hydroxyl groups, and other contaminants due to the environment. This makes it extremely difficult to determine the structure of the active SAC site using current techniques. To be tractable, computations aimed at modeling SAC utilize periodic boundary conditions and low-index facets of an idealized support. Thus, the reaction barriers and mechanisms determined computationally represent, at best, a plausibility argument, and there is a strong chance that some critical aspect is omitted. One way to better understand what is plausible is by experimental modeling, i.e., comparing the results of computations to experiments based on precisely defined single-crystalline supports prepared in an ultrahigh-vacuum (UHV) environment. In this review, we report the status of the surface-science literature as it pertains to SAC. We focus on experimental work on supports where the site of the metal atom are unambiguously determined from experiment, in particular, the surfaces of rutile and anatase TiO2, the iron oxides Fe2O3 and Fe3O4, as well as CeO2 and MgO. Much of this work is based on scanning probe microscopy in conjunction with spectroscopy, and we highlight the remarkably few studies in which metal atoms are stable on low-index surfaces of typical supports. In the Perspective section, we discuss the possibility for expanding such studies into other relevant supports.
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Affiliation(s)
- Florian Kraushofer
- Institute of Applied Physics, Technische Universitat Wien, 1040 Vienna, Austria
| | - Gareth S Parkinson
- Institute of Applied Physics, Technische Universitat Wien, 1040 Vienna, Austria
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5
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Pacchioni G, Rahman TS. Defect engineering of oxide surfaces: dream or reality? JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:291501. [PMID: 35504272 DOI: 10.1088/1361-648x/ac6c6d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Accepted: 05/03/2022] [Indexed: 06/14/2023]
Abstract
In this brief perspective we analyze the present status of the field of defect engineering of oxide surfaces. In particular we discuss the tools and techniques available to generate, identify, quantify, and characterize point defects at oxide surfaces and the main areas where these centers play a role in practical applications.
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Affiliation(s)
- Gianfranco Pacchioni
- Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, via R. Cozzi 55, 202125, Milano, Italy
| | - Talat S Rahman
- Department of Physics, University of Central Florida, Orlando, FL 32816, United States of America
- Renewable Energy and Chemical Transformation Cluster, University of Central Florida, Orlando, FL 32816, United States of America
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6
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Adegoke KA, Maxakato NW. Porous metal oxide electrocatalytic nanomaterials for energy conversion: Oxygen defects and selection techniques. Coord Chem Rev 2022. [DOI: 10.1016/j.ccr.2021.214389] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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7
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Quertite K, Enriquez H, Trcera N, Bendounan A, Mayne AJ, Dujardin G, El Kenz A, Benyoussef A, Dappe YJ, Kara A, Oughaddou H. Electron beam analysis induces Cl vacancy defects in a NaCl thin film. NANOTECHNOLOGY 2021; 33:095706. [PMID: 34814126 DOI: 10.1088/1361-6528/ac3c79] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Accepted: 11/23/2021] [Indexed: 06/13/2023]
Abstract
This work reports on the electron-induced modification of NaCl thin film grown on Ag(110). We show using low energy electron diffraction that electron beam bombardment leads to desorption and formation of Cl vacancy defects on NaCl surface. The topographic structure of these defects is studied using scanning tunneling microscopy (STM) showing the Cl defects as depressions on the NaCl surface. Most of the observed defects are mono-atomic vacancies and are located on flat NaCl terraces. Auger electron spectroscopy confirms the effect of electron exposure on NaCl thin films showing Cl atoms desorption from the surface. Using density functional theory taken into account the van der Waals dispersion interactions, we confirm the observed experimental STM measurements with STM simulation. Furthermore, comparing the adsorption of defect free NaCl and defective NaCl monolayer on Ag(110) surfaces, we found an increase of the adhesion energy and the charge transfer between the NaCl film and the substrate due to the Cl vacancy. In details, the adhesion energy increases between the NaCl film and the metallic Ag substrate from 30.4 meV Å-2for the NaCl film without Cl vacancy and from 39.5 meV Å-2for NaCl film with a single Cl vacancy. The charge transfer from the NaCl film to the Ag substrate is enhanced when the vacancy is created, from 0.63e-to 1.25e-.
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Affiliation(s)
- Khalid Quertite
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay (ISMO), Bât. 520, F-91405 Orsay, France
- Synchrotron Soleil, L'Orme des Merisiers, Saint-Aubin, B.P. 48, F-91192 Gif-sur-Yvette Cedex, France
- LaMCScI, Faculté des Sciences, Université Mohammed V-Agdal, 10100, Rabat, Morocco
| | - Hanna Enriquez
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay (ISMO), Bât. 520, F-91405 Orsay, France
| | - Nicolas Trcera
- Synchrotron Soleil, L'Orme des Merisiers, Saint-Aubin, B.P. 48, F-91192 Gif-sur-Yvette Cedex, France
| | - Azzedine Bendounan
- Synchrotron Soleil, L'Orme des Merisiers, Saint-Aubin, B.P. 48, F-91192 Gif-sur-Yvette Cedex, France
| | - Andrew J Mayne
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay (ISMO), Bât. 520, F-91405 Orsay, France
| | - Gérald Dujardin
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay (ISMO), Bât. 520, F-91405 Orsay, France
| | - Abdallah El Kenz
- LaMCScI, Faculté des Sciences, Université Mohammed V-Agdal, 10100, Rabat, Morocco
| | - Abdelilah Benyoussef
- LaMCScI, Faculté des Sciences, Université Mohammed V-Agdal, 10100, Rabat, Morocco
- Hassan II Academy of Sciences and Technology, Rabat, Morocco
| | - Yannick J Dappe
- Université Paris-Saclay, CEA, CNRS, SPEC, F-91191 Gif-sur-Yvette Cedex, France
| | - Abdelkader Kara
- Department of Physics, University of Central Florida, Orlando, FL 32816, United States of America
| | - Hamid Oughaddou
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay (ISMO), Bât. 520, F-91405 Orsay, France
- Département de Physique, CY, Cergy Paris Université, F-95031 Cergy-Pontoise Cedex, France
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8
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Gloystein A, Nilius N, Noguera C, Goniakowski J. Termination-dependent electronic structure and atomic-scale screening behavior of the Cu 2O(111) surface. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:484001. [PMID: 34500440 DOI: 10.1088/1361-648x/ac2534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Accepted: 09/09/2021] [Indexed: 06/13/2023]
Abstract
By combining differential conductance (dI/dV) spectroscopy with a scanning tunneling microscope and hybrid density functional theory simulations we explore the electronic characteristics of the (1 × 1) and (√3 × √3)R30° terminations of the Cu2O(111) surface close to thermodynamic equilibrium. Although frequently observed experimentally, the composition and atomic structure of these two terminations remain controversial. Our results show that their measured electronic signatures, such as the conduction band onset deduced from dI/dVmeasurements, the bias-dependent appearance of surface topographic features, as well as the work function retrieved from field emission resonances unambiguously confirm their recent assignment to a (1 × 1) Cu-deficient (CuD) and a (√3 × √3)R30° nano-pyramidal reconstruction. Moreover, we demonstrate that due to a different localization of the screening charges at these Cu-deficient terminations, their electronic characteristics qualitatively differ from those of the stoichiometric (1 × 1) and O-deficient (√3 × √3) terminations often assumed in the literature. As a consequence, aside from the topographic differences recently pointed out, also their electronic characteristics may contribute to a radical change in the common perception of the Cu2O(111) surface reactivity.
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Affiliation(s)
- Alexander Gloystein
- Carl von Ossietzky Universität, Institut für Physik, D-26111 Oldenburg, Germany
| | - Niklas Nilius
- Carl von Ossietzky Universität, Institut für Physik, D-26111 Oldenburg, Germany
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9
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Ninova S, Malcıoğlu OB, Auburger P, Franke M, Lytken O, Steinrück HP, Bockstedte M. Morphology dependent interaction between Co(II)-tetraphenylporphyrin and the MgO(100) surface. Phys Chem Chem Phys 2021; 23:2105-2116. [PMID: 33437981 PMCID: PMC8431532 DOI: 10.1039/d0cp04859c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Porphyrins are key elements in organic–inorganic hybrid systems for a wide range of applications. Understanding their interaction with the substrate gives a handle on structural and electronic device properties. Here we investigate a single transition-metal porphyrin, namely Co(ii)-tetraphenylporphyrin (CoTPP), on the MgO(100) surface and the effect of multilayer film formation within hybrid density-functional theory and many-body perturbation theory. We focus on the relevant adsorption sites, simulate their photoemission spectra as a key fingerprint and compare with experiments on MgO(100) films on Ag(100). While we find only weak interaction between the cobalt centre and terrace sites on the MgO(100) surface, a strong interaction manifests itself with the low-coordinated sites. This leads to distinct features in both the valence and core-level regions of the electronic structure, as observed in the ultraviolet and X-ray photoemission spectra, corroborated by simulated spectra and calculated cobalt core-level shifts. Our work thus demonstrates the relevance of morphology-related low-coordinated sites and their properties in the adsorption of CoTPP on the MgO(100) surface. The adsorption of Co-tetraphenylporphyrin at relevant low-coordinated sites on MgO(100) shows distinct features from terrace-site and multilayer films in the near-valence and corelevel regions of the electronic structure.![]()
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Affiliation(s)
- Silviya Ninova
- Chemistry and Physics of Materials, Paris-Lodron University Salzburg, Jakob-Haringer-Str. 2a, A-5020 Salzburg, Austria.
| | - Osman Barış Malcıoğlu
- Chemistry and Physics of Materials, Paris-Lodron University Salzburg, Jakob-Haringer-Str. 2a, A-5020 Salzburg, Austria.
| | - Philipp Auburger
- Theoretische Festkörperphysik, Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudtstr. 7B2, D-91058 Erlangen, Germany
| | - Matthias Franke
- Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 3, D-91058 Erlangen, Germany
| | - Ole Lytken
- Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 3, D-91058 Erlangen, Germany
| | - Hans-Peter Steinrück
- Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 3, D-91058 Erlangen, Germany
| | - Michel Bockstedte
- Chemistry and Physics of Materials, Paris-Lodron University Salzburg, Jakob-Haringer-Str. 2a, A-5020 Salzburg, Austria. .,Theoretische Festkörperphysik, Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudtstr. 7B2, D-91058 Erlangen, Germany.,Institut für Theoretische Physik, Johannes-Kepler-Universität Linz, Altenberger Str. 68, A-4040 Linz, Austria
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10
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Freund HJ, Heyde M, Kuhlenbeck H, Nilius N, Risse T, Schmidt T, Shaikhutdinov S, Sterrer M. Chapter model systems in heterogeneous catalysis at the atomic level: a personal view. Sci China Chem 2020. [DOI: 10.1007/s11426-019-9671-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
AbstractThe review presents an overview of studies in the surface science of oxide and related surfaces with an emphasis of the studies performed in the authors’ group. Novel instruments and technique developments, as well as their applications are reported, in an attempt to cover studies on model systems of increasing complexity, including some of the key ingredients of an industrially applied heterogeneous catalyst and its fabrication. The review is intended to demonstrate the power of model studies in understanding heterogeneous catalysis at the atomic level. The studies include those on supported nano-particles, both, prepared in vacuum and from solution, interaction of surfaces and the underlying bulk with molecules from the gas phase, strong metal support interaction, as well as the first attempt to include studies on reactions in confined spaces.
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11
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Therrien AJ, Hensley AJR, Zhang R, Pronschinske A, Marcinkowski MD, McEwen JS, Sykes ECH. Characterizing the geometric and electronic structure of defects in the “29” copper surface oxide. J Chem Phys 2017; 147:224706. [DOI: 10.1063/1.4996729] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Affiliation(s)
- Andrew J. Therrien
- Department of Chemistry, Tufts University, Medford, Massachusetts 02155, USA
| | - Alyssa J. R. Hensley
- The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, Washington 99164, USA
| | - Renqin Zhang
- The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, Washington 99164, USA
| | - Alex Pronschinske
- Department of Chemistry, Tufts University, Medford, Massachusetts 02155, USA
| | | | - Jean-Sabin McEwen
- The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, Washington 99164, USA
- Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164, USA
- Department of Chemistry, Washington State University, Pullman, Washington 99164, USA
- Institute for Integrated Catalysis, Pacific Northwest National Laboratory, Richland, Washington 99352, USA
| | - E. Charles H. Sykes
- Department of Chemistry, Tufts University, Medford, Massachusetts 02155, USA
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12
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Schneider WD, Heyde M, Freund HJ. Charge Control in Model Catalysis: The Decisive Role of the Oxide-Nanoparticle Interface. Chemistry 2017; 24:2317-2327. [PMID: 28857287 DOI: 10.1002/chem.201703169] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Indexed: 11/06/2022]
Abstract
In chemistry and physics the electronic charge on a species or material is one important determinant of its properties. In the present Minireview, the essential requirements for a model catalyst system suitable to study charge control are discussed. The ideal model catalyst for this purpose consists of a material system, which comprises a single crystal metal support, covered by an epitaxially grown ultrathin oxide film, and flat, two-dimensional nanoparticles residing on this film. Several examples from the literature are selected and presented, which illustrate various aspects of electron transport from the support to the nanoparticle and vice versa. Key experiments demonstrate charge control within such model catalysts and give direct evidence for a chemical reaction at the perimeter of Au nanoparticles. The concepts derived from these studies are then taken a step further to see how they may be applied for bulk powder oxide supported nanoparticles as they are frequently found in catalytically active materials.
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Affiliation(s)
- Wolf-Dieter Schneider
- Department of Chemical Physics, Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195, Berlin, Germany
| | - Markus Heyde
- Department of Chemical Physics, Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195, Berlin, Germany
| | - Hans-Joachim Freund
- Department of Chemical Physics, Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195, Berlin, Germany
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13
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Ruiz Puigdollers A, Schlexer P, Tosoni S, Pacchioni G. Increasing Oxide Reducibility: The Role of Metal/Oxide Interfaces in the Formation of Oxygen Vacancies. ACS Catal 2017. [DOI: 10.1021/acscatal.7b01913] [Citation(s) in RCA: 423] [Impact Index Per Article: 60.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Antonio Ruiz Puigdollers
- Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, via R. Cozzi, 55 I-20125 Milano, Italy
| | - Philomena Schlexer
- Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, via R. Cozzi, 55 I-20125 Milano, Italy
| | - Sergio Tosoni
- Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, via R. Cozzi, 55 I-20125 Milano, Italy
| | - Gianfranco Pacchioni
- Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, via R. Cozzi, 55 I-20125 Milano, Italy
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14
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15
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Freund HJ. Models for heterogeneous catalysts: studies at the atomic level. RENDICONTI LINCEI-SCIENZE FISICHE E NATURALI 2016. [DOI: 10.1007/s12210-016-0560-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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16
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Schneider J, Franke M, Gurrath M, Röckert M, Berger T, Bernardi J, Meyer B, Steinrück HP, Lytken O, Diwald O. Porphyrin Metalation at MgO Surfaces: A Spectroscopic and Quantum Mechanical Study on Complementary Model Systems. Chemistry 2015; 22:1744-9. [PMID: 26682774 DOI: 10.1002/chem.201503661] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Indexed: 11/05/2022]
Abstract
We show that both single-crystalline and nanostructured MgO surfaces convert free-base tetraphenyl porphyrin (2HTPP) into magnesium tetraphenyl porphyrin (MgTPP) at room temperature. The reaction can be viewed as an ion exchange between the two aminic protons of the 2HTPP molecule with a Mg(2+) ion from the surface. The driving force for the reaction is the strong stability of the formed hydroxyl groups along the steps and at defects on the MgO surface. We have used an integrated characterization approach that includes UV/Vis diffuse reflectance measurements on nanostructured powders, X-ray photoelectron spectroscopic investigation of atomically clean MgO(100) single-crystalline thin films, and density functional theory (DFT) calculations on model systems. The DFT calculations demonstrate that MgTPP formation is strongly exothermic at the corners, edges and steps, but slightly endothermic on terrace sites. This agrees well with the UV/Vis diffuse reflectance, which upon adsorption of 2HTPP shows a decrease in the absorption band associated with corner and edge sites on MgO nanocube powders.
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Affiliation(s)
- Johannes Schneider
- Department of Chemistry & Physics of Materials, Paris-Lodron University Salzburg, Salzburg, Austria
| | - Matthias Franke
- Institute of Physical Chemistry II, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany
| | - Martin Gurrath
- Interdisciplinary Center for Molecular Materials (ICMM) and Computer-Chemistry-Center (CCC), Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany
| | - Michael Röckert
- Institute of Physical Chemistry II, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany
| | - Thomas Berger
- Department of Chemistry & Physics of Materials, Paris-Lodron University Salzburg, Salzburg, Austria
| | - Johannes Bernardi
- University Service Centre for Transmission Electron Microscopy, Vienna University of Technology, Vienna, Austria
| | - Bernd Meyer
- Interdisciplinary Center for Molecular Materials (ICMM) and Computer-Chemistry-Center (CCC), Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
| | - Hans-Peter Steinrück
- Institute of Physical Chemistry II, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany
| | - Ole Lytken
- Institute of Physical Chemistry II, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
| | - Oliver Diwald
- Department of Chemistry & Physics of Materials, Paris-Lodron University Salzburg, Salzburg, Austria.
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Schwach P, Frandsen W, Willinger MG, Schlögl R, Trunschke A. Structure sensitivity of the oxidative activation of methane over MgO model catalysts: I. Kinetic study. J Catal 2015. [DOI: 10.1016/j.jcat.2015.05.007] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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18
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19
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Nilius N. Exploring routes to tailor the physical and chemical properties of oxides via doping: an STM study. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:303001. [PMID: 26151239 DOI: 10.1088/0953-8984/27/30/303001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Doping opens fascinating possibilities for tailoring the electronic, optical, magnetic, and chemical properties of oxides. The dopants perturb the intrinsic behavior of the material by generating charge centers for electron transfer into adsorbates, by inducing new energy levels for electronic and optical excitations, and by altering the surface morphology and hence the adsorption and reactivity pattern. Despite a vivid scientific interest, knowledge on doped oxides is limited when compared to semiconductors, which reflects the higher complexity and the insulating nature of many oxides. In fact, atomic-scale studies, aiming at a mechanistic understanding of dopant-related processes, are still scarce.In this article, we review our scanning tunneling microscopy (STM) experiments on thin, crystalline oxide films with a defined doping level. We demonstrate how the impurities alter the surface morphology and produce cationic/anionic vacancies in order to keep the system charge neutral. We discuss how individual dopants can be visualized in the lattice, even if they reside in subsurface layers. By means of STM-conductance and x-ray photoelectron spectroscopy, we determine the electronic impact of dopants, including the energies of their eigen states and local band-bending effects in the host oxide. Electronic transitions between dopant-induced gap states give rise to new optical modes, as detected with STM luminescence spectroscopy. From a chemical perspective, dopants are introduced to improve the redox potential of oxide materials. Electron transfer from Mo-donors, for example, alters the growth behavior of gold and activates O2 molecules on a wide-gap CaO surface. Such results demonstrate the enormous potential of doped oxides in heterogeneous catalysis. Our experiments address the issue of doping from a fundamental viewpoint, posing questions on the lattice position, charge state, and electron-transfer potential of the impurity ions. Whether doped oxides are suitable to catalyze surface reactions needs to be explored in more applied studies in the future.
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Affiliation(s)
- Niklas Nilius
- University of Oldenburg, Institute of Physics, Carl v. Ossietzky Str. 9-11, D-26111 Oldenburg, Germany
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20
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Mohr S, Xu T, Döpper T, Laurin M, Görling A, Libuda J. Molecular Orientation and Structural Transformations in Phthalic Anhydride Thin Films on MgO(100)/Ag(100). LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:7806-7814. [PMID: 26102241 DOI: 10.1021/acs.langmuir.5b01392] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Structural control of organic thin films on dielectric substrates is the key to tailoring the physical properties of hybrid materials, for example, for application in solar energy conversion, molecular electronics, or catalysis. In this work, we investigate the molecular orientation of phthalic anhydride (PAA) films on atomically well-defined MgO(100) on Ag(100) using temperature-programmed infrared reflection absorption spectroscopy (TP-IRAS) in combination with density-functional theory (DFT). A robust procedure is presented to determine the orientation of the PAA molecules, which relies on the intensity ratios of vibrational bands only. We show that even at deposition temperatures of 110 K, the PAA multilayer grows with a specific molecular orientation; that is, the PAA molecular plane is preferentially aligned parallel with the MgO surface. No change of molecular orientation occurs up to a temperature of 145 K. Between 145 and 160 K, the film restructures adopting a nearly flat-lying molecular orientation. Between 170 and 205 K, the film undergoes a second structural transition to a crystalline phase. This transition is associated with a pronounced molecular reorientation. The molecules adopt a tilted orientation and, simultaneously, rotate around their C2 axes. The reorientation behavior suggests that the molecular orientation in the crystalline phase is controlled by the interaction with the MgO(100) substrate. At higher temperature, no further restructuring is observed until the PAA multilayer desorbs at temperatures above 230 K.
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Affiliation(s)
- Susanne Mohr
- †Lehrstuhl für Physikalische Chemie II, ‡Lehrstuhl für Theoretische Chemie, and §Erlangen Catalysis Resource Center and Interdisciplinary Center Interface-Controlled Processes, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstrasse 3, D-91058 Erlangen, Germany
| | - Tao Xu
- †Lehrstuhl für Physikalische Chemie II, ‡Lehrstuhl für Theoretische Chemie, and §Erlangen Catalysis Resource Center and Interdisciplinary Center Interface-Controlled Processes, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstrasse 3, D-91058 Erlangen, Germany
| | - Tibor Döpper
- †Lehrstuhl für Physikalische Chemie II, ‡Lehrstuhl für Theoretische Chemie, and §Erlangen Catalysis Resource Center and Interdisciplinary Center Interface-Controlled Processes, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstrasse 3, D-91058 Erlangen, Germany
| | - Mathias Laurin
- †Lehrstuhl für Physikalische Chemie II, ‡Lehrstuhl für Theoretische Chemie, and §Erlangen Catalysis Resource Center and Interdisciplinary Center Interface-Controlled Processes, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstrasse 3, D-91058 Erlangen, Germany
| | - Andreas Görling
- †Lehrstuhl für Physikalische Chemie II, ‡Lehrstuhl für Theoretische Chemie, and §Erlangen Catalysis Resource Center and Interdisciplinary Center Interface-Controlled Processes, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstrasse 3, D-91058 Erlangen, Germany
| | - Jörg Libuda
- †Lehrstuhl für Physikalische Chemie II, ‡Lehrstuhl für Theoretische Chemie, and §Erlangen Catalysis Resource Center and Interdisciplinary Center Interface-Controlled Processes, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstrasse 3, D-91058 Erlangen, Germany
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21
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Stiehler C, Calaza F, Schneider WD, Nilius N, Freund HJ. Molecular Adsorption Changes the Quantum Structure of Oxide-Supported Gold Nanoparticles: Chemisorption versus Physisorption. PHYSICAL REVIEW LETTERS 2015; 115:036804. [PMID: 26230817 DOI: 10.1103/physrevlett.115.036804] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Indexed: 06/04/2023]
Abstract
STM conductance spectroscopy and mapping has been used to analyze the impact of molecular adsorption on the quantized electronic structure of individual metal nanoparticles. For this purpose, isophorone and CO2, as prototype molecules for physisorptive and chemisorptive binding, were dosed onto monolayer Au islands grown on MgO thin films. The molecules attach exclusively to the metal-oxide boundary, while the interior of the islands remains pristine. The Au quantum well states are perturbed due to the adsorption process and increase their mutual energy spacing in the CO2 case but move together in isophorone-covered islands. The shifts disclose the nature of the molecule-Au interaction, which relies on electron exchange for the CO2 ligands but on dispersive forces for the organic species. Our experiments reveal how molecular adsorption affects individual quantum systems, a topic of utmost relevance for heterogeneous catalysis.
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Affiliation(s)
| | - Florencia Calaza
- Fritz-Haber-Institut der MPG, Faradayweg 4-6, 14195 Berlin, Germany
| | - Wolf-Dieter Schneider
- Fritz-Haber-Institut der MPG, Faradayweg 4-6, 14195 Berlin, Germany
- Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | - Niklas Nilius
- Fritz-Haber-Institut der MPG, Faradayweg 4-6, 14195 Berlin, Germany
- Carl von Ossietzky Universität, 26111 Oldenburg, Germany
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22
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Li Z, Chen HYT, Schouteden K, Lauwaet K, Janssens E, Van Haesendonck C, Pacchioni G, Lievens P. Lateral manipulation of atomic vacancies in ultrathin insulating films. ACS NANO 2015; 9:5318-5325. [PMID: 25769024 DOI: 10.1021/acsnano.5b00840] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
During the last 20 years, using scanning tunneling microscopy (STM) and atomic force microscopy, scientists have successfully achieved vertical and lateral repositioning of individual atoms on and in different types of surfaces. Such atom manipulation allows the bottom-up assembly of novel nanostructures that can otherwise not be fabricated. It is therefore surprising that controlled repositioning of virtual atoms, i.e., atomic vacancies, across atomic lattices has not yet been achieved experimentally. Here we use STM at liquid helium temperature (4.5 K) to create individual Cl vacancies and subsequently to laterally manipulate them across the surface of ultrathin sodium chloride films. This allows monitoring the interactions between two neighboring vacancies with different separations. Our findings are corroborated by density functional theory calculations and STM image simulations. The lateral manipulation of atomic vacancies opens up a new playground for the investigation of fundamental physical properties of vacancy nanostructures of any size and shape and their coupling with the supporting substrate, and of the interaction of various deposits with charged vacancies.
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Affiliation(s)
- Zhe Li
- †Laboratory of Solid-State Physics and Magnetism, KU Leuven, Celestijnenlaan 200 d, Box 2414, BE-3001 Leuven, Belgium
| | - Hsin-Yi Tiffany Chen
- ‡Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, Via Cozzi 55, I-20125 Milano, Italy
| | - Koen Schouteden
- †Laboratory of Solid-State Physics and Magnetism, KU Leuven, Celestijnenlaan 200 d, Box 2414, BE-3001 Leuven, Belgium
| | - Koen Lauwaet
- †Laboratory of Solid-State Physics and Magnetism, KU Leuven, Celestijnenlaan 200 d, Box 2414, BE-3001 Leuven, Belgium
| | - Ewald Janssens
- †Laboratory of Solid-State Physics and Magnetism, KU Leuven, Celestijnenlaan 200 d, Box 2414, BE-3001 Leuven, Belgium
| | - Chris Van Haesendonck
- †Laboratory of Solid-State Physics and Magnetism, KU Leuven, Celestijnenlaan 200 d, Box 2414, BE-3001 Leuven, Belgium
| | - Gianfranco Pacchioni
- ‡Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, Via Cozzi 55, I-20125 Milano, Italy
| | - Peter Lievens
- †Laboratory of Solid-State Physics and Magnetism, KU Leuven, Celestijnenlaan 200 d, Box 2414, BE-3001 Leuven, Belgium
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23
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Calaza F, Stiehler C, Fujimori Y, Sterrer M, Beeg S, Ruiz-Oses M, Nilius N, Heyde M, Parviainen T, Honkala K, Häkkinen H, Freund HJ. Carbon Dioxide Activation and Reaction Induced by Electron Transfer at an Oxide-Metal Interface. Angew Chem Int Ed Engl 2015; 54:12484-7. [DOI: 10.1002/anie.201501420] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Revised: 03/15/2015] [Indexed: 11/07/2022]
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24
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Calaza F, Stiehler C, Fujimori Y, Sterrer M, Beeg S, Ruiz-Oses M, Nilius N, Heyde M, Parviainen T, Honkala K, Häkkinen H, Freund HJ. Aktivierung und Elektronentransfer-induzierte Reaktion von Kohlendioxid an einer Oxid-Metall-Grenzfläche. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201501420] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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25
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Pacchioni G. Numerical Simulations of Defective Structures: The Nature of Oxygen Vacancy in Non-reducible (MgO, SiO2, ZrO2) and Reducible (TiO2, NiO, WO3) Oxides. ACTA ACUST UNITED AC 2015. [DOI: 10.1007/978-3-319-14367-5_1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
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26
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Pacchioni G. First Principles Calculations on Oxide-Based Heterogeneous Catalysts and Photocatalysts: Problems and Advances. Catal Letters 2014. [DOI: 10.1007/s10562-014-1386-2] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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27
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Kullgren J, Wolf MJ, Castleton CWM, Mitev P, Briels WJ, Hermansson K. Oxygen vacancies versus fluorine at CeO2(111): a case of mistaken identity? PHYSICAL REVIEW LETTERS 2014; 112:156102. [PMID: 24785057 DOI: 10.1103/physrevlett.112.156102] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2013] [Indexed: 05/25/2023]
Abstract
We propose a resolution to the puzzle presented by the surface defects observed with STM at the (111) surface facet of CeO 2 single crystals. In the seminal paper of Esch et al. [Science 309, 752 (2005)] they were identified with oxygen vacancies, but the observed behavior of these defects is inconsistent with the results of density functional theory (DFT) studies of oxygen vacancies in the literature. We resolve these inconsistencies via DFT calculations of the properties of both oxygen vacancies and fluorine impurities at CeO2(111), the latter having recently been shown to exist in high concentrations in single crystals from a widely used commercial source of such samples. We find that the simulated filled-state STM images of surface-layer oxygen vacancies and fluorine impurities are essentially identical, which would render problematic their experimental distinction by such images alone. However, we find that our theoretical results for the most stable location, mobility, and tendency to cluster, of fluorine impurities are consistent with experimental observations, in contrast to those for oxygen vacancies. Based on these results, we propose that the surface defects observed in STM experiments on CeO2 single crystals reported heretofore were not oxygen vacancies, but fluorine impurities. Since the similarity of the simulated STM images of the two defects is due primarily to the relative energies of the 2p states of oxygen and fluorine ions, this confusion might also occur for other oxides which have been either doped or contaminated with fluorine.
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Affiliation(s)
- J Kullgren
- Department of Chemistry-Ångström, Uppsala University, Box 538, S-751 21 Uppsala, Sweden
| | - M J Wolf
- Department of Chemistry-Ångström, Uppsala University, Box 538, S-751 21 Uppsala, Sweden and Department of Physics & Astronomy, University College London, London WC1E 6BT, United Kingdom
| | - C W M Castleton
- School of Science and Technology, Nottingham Trent University, Nottingham NG11 8NS, United Kingdom
| | - P Mitev
- Department of Chemistry-Ångström, Uppsala University, Box 538, S-751 21 Uppsala, Sweden
| | - W J Briels
- Computational Biophysics, Twente University, P.O. Box 217, AE Enschede 7500, The Netherlands
| | - K Hermansson
- Department of Chemistry-Ångström, Uppsala University, Box 538, S-751 21 Uppsala, Sweden
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28
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Baumann S, Rau IG, Loth S, Lutz CP, Heinrich AJ. Measuring the three-dimensional structure of ultrathin insulating films at the atomic scale. ACS NANO 2014; 8:1739-1744. [PMID: 24377286 DOI: 10.1021/nn4061034] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The increasing technological importance of thin insulating layers calls for a thorough understanding of their structure. Here we apply scanning probe methods to investigate the structure of ultrathin magnesium oxide (MgO) which is the insulating material of choice in spintronic applications. A combination of force and current measurements gives high spatial resolution maps of the local three-dimensional insulator structure. When force measurements are not available, a lower spatial resolution can be obtained from tunneling images at different voltages. These broadly applicable techniques reveal a previously unknown complexity in the structure of MgO on Ag(001), such as steps in the insulator-metal interface.
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Affiliation(s)
- Susanne Baumann
- IBM Almaden Research Center , 650 Harry Road, San Jose, California 95120, United States
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29
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Cui Y, Shao X, Prada S, Giordano L, Pacchioni G, Freund HJ, Nilius N. Surface defects and their impact on the electronic structure of Mo-doped CaO films: an STM and DFT study. Phys Chem Chem Phys 2014; 16:12764-72. [DOI: 10.1039/c4cp01565g] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Scanning tunneling microscopy and DFT calculations are used to probe the local electronic structure of a Mo-doped CaO film.
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Affiliation(s)
- Yi Cui
- Fritz-Haber-Institut der Max-Planck-Gesellschaft
- D-14195 Berlin, Germany
| | - Xiang Shao
- Fritz-Haber-Institut der Max-Planck-Gesellschaft
- D-14195 Berlin, Germany
| | - Stefano Prada
- Dipartimento di Scienza dei Materiali
- Università di Milano-Bicocca
- 20125 Milano, Italy
| | - Livia Giordano
- Dipartimento di Scienza dei Materiali
- Università di Milano-Bicocca
- 20125 Milano, Italy
| | - Gianfranco Pacchioni
- Dipartimento di Scienza dei Materiali
- Università di Milano-Bicocca
- 20125 Milano, Italy
| | | | - Niklas Nilius
- Fritz-Haber-Institut der Max-Planck-Gesellschaft
- D-14195 Berlin, Germany
- Institut für Physik
- Carl von Ossietzky Universität Oldenburg
- D-26111 Oldenburg, Germany
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30
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Luches P, Pagliuca F, Valeri S. Structural and morphological modifications of thermally reduced cerium oxide ultrathin epitaxial films on Pt(111). Phys Chem Chem Phys 2014; 16:18848-57. [DOI: 10.1039/c4cp02723j] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Thermal treatments under vacuum and oxygen induce reversible modifications in the stoichiometry, surface morphology and structure of epitaxial CeO2 films.
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Affiliation(s)
- P. Luches
- Istituto Nanoscienze – CNR
- 41125 Modena, Italy
| | - F. Pagliuca
- Istituto Nanoscienze – CNR
- 41125 Modena, Italy
- Dipartimento di Scienze Fisiche Informatiche e Matematiche
- 41125 Modena, Italy
| | - S. Valeri
- Istituto Nanoscienze – CNR
- 41125 Modena, Italy
- Dipartimento di Scienze Fisiche Informatiche e Matematiche
- 41125 Modena, Italy
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31
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Freund HJ, Nilius N, Risse T, Schauermann S. A fresh look at an old nano-technology: catalysis. Phys Chem Chem Phys 2014; 16:8148-67. [DOI: 10.1039/c3cp55231d] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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32
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Gonchar A, Risse T. Characterisation of paramagnetic Mo impurities on MgO(100) single-crystalline films grown on Mo(100). Mol Phys 2013. [DOI: 10.1080/00268976.2013.811305] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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33
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Towards Realistic Surface Science Models of Heterogeneous Catalysts: Influence of Support Hydroxylation and Catalyst Preparation Method. Catal Letters 2013. [DOI: 10.1007/s10562-013-0987-5] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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34
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Zhu J, Lin S, Wen X, Fang Z, Li Y, Zhang Y, Huang X, Ning L, Ding K, Chen W. Deposition of (WO3)3 nanoclusters on the MgO(001) surface: A possible way to identify the charge states of the defect centers. J Chem Phys 2013; 138:034711. [DOI: 10.1063/1.4776219] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
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35
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Pacchioni G. Electronic interactions and charge transfers of metal atoms and clusters on oxide surfaces. Phys Chem Chem Phys 2013; 15:1737-57. [DOI: 10.1039/c2cp43731g] [Citation(s) in RCA: 175] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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36
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Ling S, Watkins MB, Shluger AL. Effects of atomic scale roughness at metal/insulator interfaces on metal work function. Phys Chem Chem Phys 2013; 15:19615-24. [DOI: 10.1039/c3cp53590h] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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37
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Surnev S, Fortunelli A, Netzer FP. Structure-property relationship and chemical aspects of oxide-metal hybrid nanostructures. Chem Rev 2012; 113:4314-72. [PMID: 23237602 DOI: 10.1021/cr300307n] [Citation(s) in RCA: 141] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- Svetlozar Surnev
- Surface and Interface Physics, Institute of Physics, Karl-Franzens University, Graz A-8010 Graz, Austria
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38
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Sousa C, Tosoni S, Illas F. Theoretical Approaches to Excited-State-Related Phenomena in Oxide Surfaces. Chem Rev 2012. [DOI: 10.1021/cr300228z] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Carmen Sousa
- Departament de Química
Física and Institut de Química Teòrica i Computacional
(IQTCUB), Universitat de Barcelona, C/Martí
i Franquès 1, 08028 Barcelona, Spain
| | - Sergio Tosoni
- Departament de Química
Física and Institut de Química Teòrica i Computacional
(IQTCUB), Universitat de Barcelona, C/Martí
i Franquès 1, 08028 Barcelona, Spain
- Departamento de Química, Universidad de Las Palmas de Gran Canaria, Campus Universitario
de Tafira, 35017 Las Palmas de Gran Canaria, Spain
| | - Francesc Illas
- Departament de Química
Física and Institut de Química Teòrica i Computacional
(IQTCUB), Universitat de Barcelona, C/Martí
i Franquès 1, 08028 Barcelona, Spain
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39
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Pacchioni G, Freund H. Electron Transfer at Oxide Surfaces. The MgO Paradigm: from Defects to Ultrathin Films. Chem Rev 2012; 113:4035-72. [DOI: 10.1021/cr3002017] [Citation(s) in RCA: 241] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Gianfranco Pacchioni
- Dipartimento di Scienza dei
Materiali, Università di Milano-Bicocca, Via R. Cozzi, 53−20125,
Milano, Italy
| | - Hajo Freund
- Fritz-Haber-Insitut
der MPG,
Department of Chemical Physics, Faradayweg 4-6, 14195 Berlin, Germany
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40
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Giordano L, Pacchioni G. Oxide films at the nanoscale: new structures, new functions, and new materials. Acc Chem Res 2011; 44:1244-52. [PMID: 21805966 DOI: 10.1021/ar200139y] [Citation(s) in RCA: 144] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
We all make use of oxide ultrathin films, even if we are unaware of doing so. They are essential components of many common devices, such as mobile phones and laptops. The films in these ubiquitous electronics are composed of silicon dioxide, an unsurpassed material in the design of transistors. But oxide films at the nanoscale (typically just 10 nm or less in thickness) are integral to many other applications. In some cases, they form under normal reactive conditions and confer new properties to a material: one example is the corrosion protection of stainless steel, which is the result of a passive film. A new generation of devices for energy production and communications technology, such as ferroelectric ultrathin film capacitors, tunneling magnetoresistance sensors, solar energy materials, solid oxide fuel cells, and many others, are being specifically designed to exploit the unusual properties afforded by reduced oxide thickness. Oxide ultrathin films also have tremendous potential in chemistry, representing a rich new source of catalytic materials. About 20 years ago, researchers began to prepare model systems of truly heterogeneous catalysts based on thin oxide layers grown on single crystals of metal. Only recently, however, was it realized that these systems may behave quite differently from their corresponding bulk oxides. One of the phenomena uncovered is the occurrence of a spontaneous charge transfer from the metal support to an adsorbed species through the thin insulating layer (or vice versa). The importance of this property is clear: conceptually, the activation and bond breaking of adsorbed molecules begin with precisely the same process, electron transfer into an antibonding orbital. But electron transfer can also be harnessed to make a supported metal particle more chemically active, increase its adhesion energy, or change its shape. Most importantly, the basic principles underlying electron transfer and other phenomena (such as structural flexibility, electronic modifications, and nanoporosity) are now largely understood, thus paving the way for the rational design of new catalytic systems based on oxide ultrathin films. Many of the mechanisms involved (electron tunneling, work function changes, defects engineering, and so forth) are typical of semiconductor physics and allow a direct link between the two fields. A related conceptual framework, the "electronic theory of catalysis", was proposed a long time ago but has been largely neglected by the catalytic community. A renewed appreciation of this catalytic framework, together with spectacular advances in modeling and electronic structure methods, now makes it possible to combine theory with advanced experimental setups and meet the challenge of designing new materials with tailored properties. In this Account, we discuss some of the recent advances with nanoscale oxide films, highlighting contributions from our laboratory. Once mastered, ultrathin oxide films on metals will provide vast and unforeseen opportunities in heterogeneous catalysis as well as in other fields of science and technology.
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Affiliation(s)
- Livia Giordano
- Dipartimento di Scienza dei Materiali, Università Milano Bicocca, via R. Cozzi 53, 53-20125 Milano, Italy
| | - Gianfranco Pacchioni
- Dipartimento di Scienza dei Materiali, Università Milano Bicocca, via R. Cozzi 53, 53-20125 Milano, Italy
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41
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Shao X, Jerratsch JF, Nilius N, Freund HJ. Probing the 4f states of ceria by tunneling spectroscopy. Phys Chem Chem Phys 2011; 13:12646-51. [PMID: 21674086 DOI: 10.1039/c1cp21113g] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Low-temperature scanning tunneling microscopy and spectroscopy have been employed to analyze the local electronic structure of the (111) surface of a ceria thin film grown on Ru(0001). On pristine, defect-free oxide terraces, the empty 4f states of Ce(4+) ions appear as the only spectral feature inside the 6 eV oxide band gap. In contrast, occupied states are detected between -1.0 and -1.5 eV below E(Fermi) in conductance spectra of different point and line defects, such as surface oxygen vacancies, grain boundaries and step edges. They are assigned to partially filled 4f states localized at the Ce(3+) ions. The presence of excess electrons indicates the oxygen-deficient nature of the direct oxide environment. The f state spectroscopy with the STM allows us to probe the spatial distribution of Ce(3+) ions in the ceria surface, providing unique insight into the local reduction state of this chemically important material system.
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Affiliation(s)
- Xiang Shao
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
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Barth C, Foster AS, Henry CR, Shluger AL. Recent trends in surface characterization and chemistry with high-resolution scanning force methods. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2011; 23:477-501. [PMID: 21254251 DOI: 10.1002/adma.201002270] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2010] [Revised: 08/20/2010] [Indexed: 05/26/2023]
Abstract
The current status and future prospects of non-contact atomic force microscopy (nc-AFM) and Kelvin probe force microscopy (KPFM) for studying insulating surfaces and thin insulating films in high resolution are discussed. The rapid development of these techniques and their use in combination with other scanning probe microscopy methods over the last few years has made them increasingly relevant for studying, controlling, and functionalizing the surfaces of many key materials. After introducing the instruments and the basic terminology associated with them, state-of-the-art experimental and theoretical studies of insulating surfaces and thin films are discussed, with specific focus on defects, atomic and molecular adsorbates, doping, and metallic nanoclusters. The latest achievements in atomic site-specific force spectroscopy and the identification of defects by crystal doping, work function, and surface charge imaging are reviewed and recent progress being made in high-resolution imaging in air and liquids is detailed. Finally, some of the key challenges for the future development of the considered fields are identified.
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Affiliation(s)
- Clemens Barth
- Centre Interdisciplinaire de Nanoscience de Marseille, Aix-Marseille University, CNRS, Marseille, France.
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König T, Simon GH, Heinke L, Lichtenstein L, Heyde M. Defects in oxide surfaces studied by atomic force and scanning tunneling microscopy. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2011; 2:1-14. [PMID: 21977410 PMCID: PMC3045939 DOI: 10.3762/bjnano.2.1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2010] [Accepted: 12/09/2010] [Indexed: 05/24/2023]
Abstract
Surfaces of thin oxide films were investigated by means of a dual mode NC-AFM/STM. Apart from imaging the surface termination by NC-AFM with atomic resolution, point defects in magnesium oxide on Ag(001) and line defects in aluminum oxide on NiAl(110), respectively, were thoroughly studied. The contact potential was determined by Kelvin probe force microscopy (KPFM) and the electronic structure by scanning tunneling spectroscopy (STS). On magnesium oxide, different color centers, i.e., F(0), F(+), F(2+) and divacancies, have different effects on the contact potential. These differences enabled classification and unambiguous differentiation by KPFM. True atomic resolution shows the topography at line defects in aluminum oxide. At these domain boundaries, STS and KPFM verify F(2+)-like centers, which have been predicted by density functional theory calculations. Thus, by determining the contact potential and the electronic structure with a spatial resolution in the nanometer range, NC-AFM and STM can be successfully applied on thin oxide films beyond imaging the topography of the surface atoms.
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Affiliation(s)
- Thomas König
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - Georg H Simon
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - Lars Heinke
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - Leonid Lichtenstein
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - Markus Heyde
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
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Freund HJ, Nilius N, Risse T, Schauermann S, Schmidt T. Innovative Measurement Techniques in Surface Science. Chemphyschem 2010; 12:79-87. [DOI: 10.1002/cphc.201000812] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2010] [Indexed: 11/08/2022]
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König T, Simon GH, Martinez U, Giordano L, Pacchioni G, Heyde M, Freund HJ. Direct measurement of the attractive interaction forces on F0 color centers on MgO(001) by dynamic force microscopy. ACS NANO 2010; 4:2510-2514. [PMID: 20438103 DOI: 10.1021/nn100443n] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Defect sites on oxide surfaces play a dominant role in surface chemistry. The direct atomistic study of these sites is important but very difficult. We have mimicked the adsorbate-defect interaction by a dynamic force microscope tip measuring the interaction with a color center (F(0)) on the MgO(001) surface. The experimental findings, complemented by density functional theory calculations, show a highly attractive adsorbate-defect interaction and a charge transfer at a critical distance.
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Affiliation(s)
- Thomas König
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
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Barcaro G, Thomas IO, Fortunelli A. Validation of density-functional versus density-functional+U approaches for oxide ultrathin films. J Chem Phys 2010; 132:124703. [DOI: 10.1063/1.3366689] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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Gonchar A, Risse T, Giamello E, Freund HJ. Additive coloring of thin, single crystalline MgO(001) films. Phys Chem Chem Phys 2010; 12:12520-4. [DOI: 10.1039/c0cp00197j] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Migani A, Vayssilov GN, Bromley ST, Illas F, Neyman KM. Dramatic reduction of the oxygen vacancy formation energy in ceria particles: a possible key to their remarkable reactivity at the nanoscale. ACTA ACUST UNITED AC 2010. [DOI: 10.1039/c0jm01908a] [Citation(s) in RCA: 171] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Bieletzki M, Hynninen T, Soini TM, Pivetta M, Henry CR, Foster AS, Esch F, Barth C, Heiz U. Topography and work function measurements of thin MgO(001) films on Ag(001) by nc-AFM and KPFM. Phys Chem Chem Phys 2010; 12:3203-9. [DOI: 10.1039/b923296f] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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