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Weyel J, Hess C. Refining the mechanism of CO 2 and H 2 activation over gold-ceria catalysts by IR modulation excitation spectroscopy. Phys Chem Chem Phys 2024; 26:6608-6615. [PMID: 38333955 DOI: 10.1039/d3cp05102a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2024]
Abstract
The activation and utilization of the greenhouse gas CO2 is of great interest for the energy transition as a fossil-free carbon source for mitigating climate change. CO2 hydrogenation via the reverse water-gas shift reaction (RWGSR) converts CO2 to CO, a crucial component of syngas, enabling further transformation by means of the Fischer-Tropsch process. In this study, we unravel the detailed mechanism of the RWGSR on low-loaded Au/CeO2 catalysts using IR modulation excitation spectroscopy (MES), by periodically modulating the concentration of the reactants, followed by phase-sensitive detection (PSD). Applying such a MES-PSD approach to Au/CeO2 catalysts during RWGSR gives direct spectroscopic evidence for the active role of gold hydride, bidentate carbonate and hydroxyl species in the reaction mechanism, while disproving the participation of other species such as formate. Our results highlight the potential of modulation excitation spectroscopy combined with phase-sensitive detection to provide new mechanistic insight into catalytic reactions not accessible by steady-state techniques, including a profound understanding of the sequence of reaction steps.
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Affiliation(s)
- Jakob Weyel
- Eduard-Zintl-Institute of Inorganic and Physical Chemistry, Technical University of Darmstadt, Peter-Grünberg-Str. 8, 64287 Darmstadt, Germany.
| | - Christian Hess
- Eduard-Zintl-Institute of Inorganic and Physical Chemistry, Technical University of Darmstadt, Peter-Grünberg-Str. 8, 64287 Darmstadt, Germany.
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2
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Jiang L, Li K, Porter WN, Wang H, Li G, Chen JG. Role of H 2O in Catalytic Conversion of C 1 Molecules. J Am Chem Soc 2024; 146:2857-2875. [PMID: 38266172 DOI: 10.1021/jacs.3c13374] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2024]
Abstract
Due to their role in controlling global climate change, the selective conversion of C1 molecules such as CH4, CO, and CO2 has attracted widespread attention. Typically, H2O competes with the reactant molecules to adsorb on the active sites and therefore inhibits the reaction or causes catalyst deactivation. However, H2O can also participate in the catalytic conversion of C1 molecules as a reactant or a promoter. Herein, we provide a perspective on recent progress in the mechanistic studies of H2O-mediated conversion of C1 molecules. We aim to provide an in-depth and systematic understanding of H2O as a promoter, a proton-transfer agent, an oxidant, a direct source of hydrogen or oxygen, and its influence on the catalytic activity, selectivity, and stability. We also summarize strategies for modifying catalysts or catalytic microenvironments by chemical or physical means to optimize the positive effects and minimize the negative effects of H2O on the reactions of C1 molecules. Finally, we discuss challenges and opportunities in catalyst design, characterization techniques, and theoretical modeling of the H2O-mediated catalytic conversion of C1 molecules.
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Affiliation(s)
- Lei Jiang
- State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization Engineering, Kunming University of Science and Technology, Kunming 650093, Yunnan, China
- Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming 650093, Yunnan, China
| | - Kongzhai Li
- State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization Engineering, Kunming University of Science and Technology, Kunming 650093, Yunnan, China
- Southwest United Graduate School, Kunming 650000, Yunnan, China
| | - William N Porter
- Department of Chemical Engineering, Columbia University, New York, New York 10027, United States
| | - Hua Wang
- State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization Engineering, Kunming University of Science and Technology, Kunming 650093, Yunnan, China
| | - Gengnan Li
- Center for Nanoscale Materials, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Jingguang G Chen
- Department of Chemical Engineering, Columbia University, New York, New York 10027, United States
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3
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Rajan A, Pushkar AP, Dharmalingam BC, Varghese JJ. Iterative multiscale and multi-physics computations for operando catalyst nanostructure elucidation and kinetic modeling. iScience 2023; 26:107029. [PMID: 37360694 PMCID: PMC10285649 DOI: 10.1016/j.isci.2023.107029] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/28/2023] Open
Abstract
Modern heterogeneous catalysis has benefitted immensely from computational predictions of catalyst structure and its evolution under reaction conditions, first-principles mechanistic investigations, and detailed kinetic modeling, which are rungs on a multiscale workflow. Establishing connections across these rungs and integration with experiments have been challenging. Here, operando catalyst structure prediction techniques using density functional theory simulations and ab initio thermodynamics calculations, molecular dynamics, and machine learning techniques are presented. Surface structure characterization by computational spectroscopic and machine learning techniques is then discussed. Hierarchical approaches in kinetic parameter estimation involving semi-empirical, data-driven, and first-principles calculations and detailed kinetic modeling via mean-field microkinetic modeling and kinetic Monte Carlo simulations are discussed along with methods and the need for uncertainty quantification. With these as the background, this article proposes a bottom-up hierarchical and closed loop modeling framework incorporating consistency checks and iterative refinements at each level and across levels.
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Affiliation(s)
- Ajin Rajan
- Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai, Tamil Nadu 600036, India
| | - Anoop P. Pushkar
- Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai, Tamil Nadu 600036, India
| | - Balaji C. Dharmalingam
- Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai, Tamil Nadu 600036, India
| | - Jithin John Varghese
- Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai, Tamil Nadu 600036, India
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4
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Muravev V, Parastaev A, van den Bosch Y, Ligt B, Claes N, Bals S, Kosinov N, Hensen EJM. Size of cerium dioxide support nanocrystals dictates reactivity of highly dispersed palladium catalysts. Science 2023; 380:1174-1179. [PMID: 37319196 DOI: 10.1126/science.adf9082] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2022] [Accepted: 05/15/2023] [Indexed: 06/17/2023]
Abstract
The catalytic performance of heterogeneous catalysts can be tuned by modulation of the size and structure of supported transition metals, which are typically regarded as the active sites. In single-atom metal catalysts, the support itself can strongly affect the catalytic properties. Here, we demonstrate that the size of cerium dioxide (CeO2) support governs the reactivity of atomically dispersed palladium (Pd) in carbon monoxide (CO) oxidation. Catalysts with small CeO2 nanocrystals (~4 nanometers) exhibit unusually high activity in a CO-rich reaction feed, whereas catalysts with medium-size CeO2 (~8 nanometers) are preferred for lean conditions. Detailed spectroscopic investigations reveal support size-dependent redox properties of the Pd-CeO2 interface.
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Affiliation(s)
- Valery Muravev
- Laboratory of Inorganic Materials and Catalysis, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, 5600 MB Eindhoven, Netherlands
| | - Alexander Parastaev
- Laboratory of Inorganic Materials and Catalysis, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, 5600 MB Eindhoven, Netherlands
| | - Yannis van den Bosch
- Laboratory of Inorganic Materials and Catalysis, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, 5600 MB Eindhoven, Netherlands
| | - Bianca Ligt
- Laboratory of Inorganic Materials and Catalysis, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, 5600 MB Eindhoven, Netherlands
| | - Nathalie Claes
- Electron Microscopy for Materials Science (EMAT), University of Antwerp, 2020 Antwerp, Belgium
| | - Sara Bals
- Electron Microscopy for Materials Science (EMAT), University of Antwerp, 2020 Antwerp, Belgium
| | - Nikolay Kosinov
- Laboratory of Inorganic Materials and Catalysis, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, 5600 MB Eindhoven, Netherlands
| | - Emiel J M Hensen
- Laboratory of Inorganic Materials and Catalysis, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, 5600 MB Eindhoven, Netherlands
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5
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Kim D, Dimitrakopoulos G, Yildiz B. Controlling the Size of Au Nanoparticles on Reducible Oxides with the Electrochemical Potential. J Am Chem Soc 2022; 144:21926-21938. [PMID: 36441525 DOI: 10.1021/jacs.2c08422] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Controlling the size of Au nanoparticles (NPs) and their interaction with the oxide support is important for their catalytic performance in chemical reactions, such as CO oxidation and water-gas shift. It is known that the oxygen vacancies at the surface of support oxides form strong chemical bonding with the Au NPs and inhibit their coarsening and deactivation. The resulting Au/oxygen vacancy interface also acts as an active site for oxidation reactions. Hence, small Au NPs are needed to increase the density of the Au/oxide interface. A dynamic way to control the size of the Au NPs on an oxide support is desirable but has been missing in the field. Here, we demonstrate an electrochemical method to control the size of the Au NPs by controlling the surface oxygen vacancy concentration of the support oxide. Oxides with different reducibilities, La0.8Ca0.2MnO3±δ and Pr0.1Ce0.9O2-δ, are used as model support oxides. By applying the electrochemical potential, we achieve a wide range of effective oxygen pressures, pO2 (10-37-1014 atm), in the support oxides. Applying the cathodic potential creates a high concentration of oxygen vacancies and forms finely distributed Au NPs with sizes of 7-13 nm at 700-770 °C in 10 min, while the anodic potential oxidizes the surface and increases the size of the Au NPs. The onset cathodic potential required to create small Au NPs depends strongly on the reducibility of the support oxide. The Au NPs did not undergo sintering even at 700-770 °C under the cathodic potential and also were stable in catalytically relevant conditions without potential.
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Affiliation(s)
- Dongha Kim
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Georgios Dimitrakopoulos
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Bilge Yildiz
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States.,Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
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6
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Sun XC, Yuan K, Hua WD, Gao ZR, Zhang Q, Yuan CY, Liu HC, Zhang YW. Weakening the Metal–Support Interactions of M/CeO 2 (M = Co, Fe, Ni) Using a NH 3-Treated CeO 2 Support for an Enhanced Water–Gas Shift Reaction. ACS Catal 2022. [DOI: 10.1021/acscatal.2c03664] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Xiao-Chen Sun
- Beijing National Laboratory for Molecular Sciences (BNLMS), State Key Laboratory of Rare Earth Materials Chemistry and Applications, PKU-HKU Joint Laboratory in Rare Earth Materials and Bioinorganic Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Kun Yuan
- Beijing National Laboratory for Molecular Sciences (BNLMS), State Key Laboratory of Rare Earth Materials Chemistry and Applications, PKU-HKU Joint Laboratory in Rare Earth Materials and Bioinorganic Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Wang-De Hua
- Beijing National Laboratory for Molecular Sciences (BNLMS), State Key Laboratory for Structural Chemistry of Stable and Unstable Species, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Zi-Rui Gao
- Beijing National Laboratory for Molecular Sciences (BNLMS), State Key Laboratory for Structural Chemistry of Stable and Unstable Species, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Qian Zhang
- Beijing National Laboratory for Molecular Sciences (BNLMS), State Key Laboratory of Rare Earth Materials Chemistry and Applications, PKU-HKU Joint Laboratory in Rare Earth Materials and Bioinorganic Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Chen-Yue Yuan
- Beijing National Laboratory for Molecular Sciences (BNLMS), State Key Laboratory of Rare Earth Materials Chemistry and Applications, PKU-HKU Joint Laboratory in Rare Earth Materials and Bioinorganic Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Hai-Chao Liu
- Beijing National Laboratory for Molecular Sciences (BNLMS), State Key Laboratory for Structural Chemistry of Stable and Unstable Species, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Ya-Wen Zhang
- Beijing National Laboratory for Molecular Sciences (BNLMS), State Key Laboratory of Rare Earth Materials Chemistry and Applications, PKU-HKU Joint Laboratory in Rare Earth Materials and Bioinorganic Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
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7
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Ziemba M, Weyel J, Hess C. Approaching C1 Reaction Mechanisms Using Combined Operando and Transient Analysis: A Case Study on Cu/CeO 2 Catalysts during the LT-Water–Gas Shift Reaction. ACS Catal 2022. [DOI: 10.1021/acscatal.2c02216] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Marc Ziemba
- Eduard Zintl Institute of Inorganic and Physical Chemistry, Technical University of Darmstadt, Alarich-Weiss-Str. 8, 64287 Darmstadt, Germany
| | - Jakob Weyel
- Eduard Zintl Institute of Inorganic and Physical Chemistry, Technical University of Darmstadt, Alarich-Weiss-Str. 8, 64287 Darmstadt, Germany
| | - Christian Hess
- Eduard Zintl Institute of Inorganic and Physical Chemistry, Technical University of Darmstadt, Alarich-Weiss-Str. 8, 64287 Darmstadt, Germany
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8
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Conversion of Alcohols on Stoichiometric and Reduced Rutile TiO2 (110): Point Defects Meet Bifunctionality in Oxide (Photo-)Chemistry. Catal Letters 2022. [DOI: 10.1007/s10562-022-04077-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
AbstractOxidic (photo-)catalysts have the potential to play an important role to efficiently implement sustainable feedstocks and green energy sources into future energy technologies. They may be used not only for solar energy harvesting, but also for hydrogen production or being essential for the fabrication of fine chemicals. Therefore, it is crucial to develop a detailed understanding of how the atomistic environment of the catalyst can be designed in order to promote distinct reaction pathways to influence the final product distribution of chemical reactions. In this perspective article, we survey the surface (photo-)chemistry of methanol on rutile TiO2 surfaces and hybrid catalysts based thereon. Especially the role of the surface bifunctionality by Lewis acidic and basic sites combined with the strong impact of point defects such as reduced titanium sites (mainly Ti3+ interstitials) shall be illuminated. It is shown how the selective activation of either O–H, C–H or C–O bonds in the methanol molecule can be used to tune not only the overall conversion, but to switch between oxidative and reductive routes in favor of either deoxygenation, partial oxidation or C–C coupling reactions. Especially the latter ones are of particular interest to introduce methanol from green sources such as biomass as a sustainable feedstock into already existing petrochemical technologies.
Graphical Abstract
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9
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Longo A, Giannici F, Casaletto MP, Rovezzi M, Sahle CJ, Glatzel P, Joly Y, Martorana A. Dynamic Role of Gold d-Orbitals during CO Oxidation under Aerobic Conditions. ACS Catal 2022. [DOI: 10.1021/acscatal.1c05739] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Alessandro Longo
- ESRF - The European Synchrotron, CS 40220, 38043 Cedex 9 Grenoble, France
- Istituto per lo Studio dei Materiali Nanostrutturati, Consiglio Nazionale delle Ricerche, Via Ugo La Malfa 153, 90146 Palermo, Italy
| | - Francesco Giannici
- Dipartimento di Fisica e Chimica, Università di Palermo, Viale delle Scienze, I-90128 Palermo, Italy
| | - Maria Pia Casaletto
- Istituto per lo Studio dei Materiali Nanostrutturati, Consiglio Nazionale delle Ricerche, Via Ugo La Malfa 153, 90146 Palermo, Italy
| | - Mauro Rovezzi
- ESRF - The European Synchrotron, CS 40220, 38043 Cedex 9 Grenoble, France
- Universitè Grenoble Alpes, CNRS, IRD, Irstea, Météo France, OSUG, FAME, 71 Avenue des Martyrs, CS 40220, 38043 Grenoble, France
| | - Christoph J. Sahle
- ESRF - The European Synchrotron, CS 40220, 38043 Cedex 9 Grenoble, France
| | - Pieter Glatzel
- ESRF - The European Synchrotron, CS 40220, 38043 Cedex 9 Grenoble, France
| | - Yves Joly
- Universitè Grenoble Alpes Inst NEEL, 38042 Grenoble (France) and CNRS, Inst NEEL, 38042 Grenoble, France
| | - Antonino Martorana
- Dipartimento di Fisica e Chimica, Università di Palermo, Viale delle Scienze, I-90128 Palermo, Italy
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Weyel J, Ziemba M, Hess C. Elucidating Active CO–Au Species on Au/CeO2(111): A Combined Modulation Excitation DRIFTS and Density Functional Theory Study. Top Catal 2022. [DOI: 10.1007/s11244-022-01599-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
AbstractIn this work we elucidate the main steps of the CO oxidation mechanism over Au/CeO2(111), clarifying the course of CO adsorption at a broad variety of surface sites as well as of transmutations of one CO species into another. By combining transient spectroscopy with DFT calculations we provide new evidence that the active centers for CO conversion are single gold atoms. To gain insight into the reaction mechanism, we employ Modulation Excitation (ME) DRIFT spectroscopy in combination with the mathematical tool of Phase Sensitive Detection to identify the active species and perform DFT calculations to facilitate the assignments of the observed bands. The transient nature of the ME-DRIFTS method allows us to sort the observed species temporally, providing further mechanistic insight. Our study highlights the potential of combined transient spectroscopy and theoretical calculations (DFT) to clarify the role of adsorbates observed and to elucidate the reaction mechanism of CO oxidation over supported gold and other noble-metal catalysts.
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Zhang Y, Zhao S, Feng J, Song S, Shi W, Wang D, Zhang H. Unraveling the physical chemistry and materials science of CeO2-based nanostructures. Chem 2021. [DOI: 10.1016/j.chempr.2021.02.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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13
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Ziemba M, Schilling C, Ganduglia-Pirovano MV, Hess C. Toward an Atomic-Level Understanding of Ceria-Based Catalysts: When Experiment and Theory Go Hand in Hand. Acc Chem Res 2021; 54:2884-2893. [PMID: 34137246 PMCID: PMC8264949 DOI: 10.1021/acs.accounts.1c00226] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
ConspectusBecause ceria (CeO2) is a key ingredient in the formulation of many catalysts, its catalytic roles have received a great amount of attention from experiment and theory. Its primary function is to enhance the oxidation activity of catalysts, which is largely governed by the low activation barrier for creating lattice O vacancies. Such an important characteristic of ceria has been exploited in CO oxidation, methane partial oxidation, volatile organic compound oxidation, and the water-gas shift (WGS) reaction and in the context of automotive applications. A great challenge of such heterogeneously catalyzed processes remains the unambiguous identification of active sites.In oxidation reactions, closing the catalytic cycle requires ceria reoxidation by gas-phase oxygen, which includes oxygen adsorption and activation. While the general mechanistic framework of such processes is accepted, only very recently has an atomic-level understanding of oxygen activation on ceria powders been achieved by combined experimental and theoretical studies using in situ multiwavelength Raman spectroscopy and DFT.Recent studies have revealed that the adsorption and activation of gas-phase oxygen on ceria is strongly facet-dependent and involves different superoxide/peroxide species, which can now be unambiguously assigned to ceria surface sites using the combined Raman and DFT approach. Our results demonstrate that, as a result of oxygen dissociation, vacant ceria lattice sites are healed, highlighting the close relationship of surface processes with lattice oxygen dynamics, which is also of technical relevance in the context of oxygen storage-release applications.A recent DFT interpretation of Raman spectra of polycrystalline ceria enables us to take account of all (sub)surface and bulk vibrational features observed in the experimental spectra and has revealed new findings of great relevance for a mechanistic understanding of ceria-based catalysts. These include the identification of surface oxygen (Ce-O) modes and the quantification of subsurface oxygen defects. Combining these theoretical insights with operando Raman experiments now allows the (sub)surface oxygen dynamics of ceria and noble metal/ceria catalysts to be monitored under the reaction conditions.Applying these findings to Au/ceria catalysts provides univocal evidence for ceria support participation in heterogeneous catalysis. For room-temperature CO oxidation, operando Raman monitoring the (sub)surface defect dynamics clearly demonstrates the dependence of catalytic activity on the ceria reduction state. Extending the combined experimental/DFT approach to operando IR spectroscopy allows the elucidation of the nature of the active gold as (pseudo)single Au+ sites and enables us to develop a detailed mechanistic picture of the catalytic cycle. Temperature-dependent studies highlight the importance of facet-dependent defect formation energies and adsorbate stabilities (e.g., carbonates). While the latter aspects are also evidenced to play a role in the WGS reaction, the facet-dependent catalytic performance shows a correlation with the extent of gold agglomeration. Our findings are fully consistent with a redox mechanism, thus adding a new perspective to the ongoing discussion of the WGS reaction.As outlined above for ceria-based catalysts, closely combining state-of-the-art in situ/operando spectroscopy and theory constitutes a powerful approach to rational catalyst design by providing essential mechanistic information based on an atomic-level understanding of reactions.
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Affiliation(s)
- Marc Ziemba
- Eduard-Zintl-Institute of Inorganic and Physical Chemistry, Technical University of Darmstadt, Alarich-Weiss-Str. 8, 64287 Darmstadt, Germany
| | - Christian Schilling
- Eduard-Zintl-Institute of Inorganic and Physical Chemistry, Technical University of Darmstadt, Alarich-Weiss-Str. 8, 64287 Darmstadt, Germany
| | - M. Verónica Ganduglia-Pirovano
- Instituto de Catálisis y Petroleoquímica - Consejo Superior de Investigaciones Científicas, Marie Curie 2, 28049 Madrid, Spain
| | - Christian Hess
- Eduard-Zintl-Institute of Inorganic and Physical Chemistry, Technical University of Darmstadt, Alarich-Weiss-Str. 8, 64287 Darmstadt, Germany
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14
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Schumacher L, Hess C. The active role of the support in propane ODH over VOx/CeO2 catalysts studied using multiple operando spectroscopies. J Catal 2021. [DOI: 10.1016/j.jcat.2021.04.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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15
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Chung CH, Tu FY, Chiu TA, Wu TT, Yu WY. Critical Roles of Surface Oxygen Vacancy in Heterogeneous Catalysis over Ceria-based Materials: A Selected Review. CHEM LETT 2021. [DOI: 10.1246/cl.200845] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Ching-Hsiu Chung
- Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan
- Advanced Research Center for Green Materials Science and Technology, Taipei 10617, Taiwan
| | - Fang-Yi Tu
- Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan
- Advanced Research Center for Green Materials Science and Technology, Taipei 10617, Taiwan
| | - Te-An Chiu
- Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan
- Advanced Research Center for Green Materials Science and Technology, Taipei 10617, Taiwan
| | - Tung-Ta Wu
- Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan
- Advanced Research Center for Green Materials Science and Technology, Taipei 10617, Taiwan
| | - Wen-Yueh Yu
- Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan
- Advanced Research Center for Green Materials Science and Technology, Taipei 10617, Taiwan
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16
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Catalytic activities of hydroxylated gold dimer clusters for water-gas shift reactions. MOLECULAR CATALYSIS 2021. [DOI: 10.1016/j.mcat.2021.111414] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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17
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Ziemba M, Ganduglia-Pirovano MV, Hess C. Insight into the mechanism of the water-gas shift reaction over Au/CeO 2 catalysts using combined operando spectroscopies. Faraday Discuss 2021; 229:232-250. [PMID: 33634801 DOI: 10.1039/c9fd00133f] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The mechanism of the low-temperature water-gas shift (LT-WGS) reaction over Au/CeO2 catalysts with different ceria terminations, i.e., (111), (110), and (100) facets, was investigated. Using combined operando Raman and UV-Vis spectroscopy as well as isotope exchange experiments, we are able to draw conclusions about the reducibility behaviour and the exchange of surface oxygen. Additional density functional theory (DFT) calculations facilitate the vibrational bands assignments and enhance the interpretation of the results on a molecular level. A facet-dependent role of gold is observed with respect to the oxygen dynamics, since for the CeO2(111) facet the presence of gold is required to exchange surface oxygen, whereas the CeO2(110) facet requires no gold, as rationalized by the low defect formation energy of this facet. This behaviour suggests that surface properties (termination, stepped surface) may have a strong effect on the reactivity. While the reduction of the support accompanies the reaction, its extent does not directly correlate with activity, highlighting the importance of other properties, such as the dissociative adsorption of water and/or CO2/H2 desorption. The results of our facet-dependent study are consistent with a redox mechanism, as underlined by H218O isotopic exchange experiments demonstrating the ready exchange of surface oxygen.
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Affiliation(s)
- Marc Ziemba
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, Alarich-Weiss-Str. 8, 64287 Darmstadt, Germany.
| | - M Verónica Ganduglia-Pirovano
- Instituto de Catálisis y Petroleoquímica - Consejo Superior de Investigaciones Científicas, Marie Curie 2, 28049 Madrid, Spain
| | - Christian Hess
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, Alarich-Weiss-Str. 8, 64287 Darmstadt, Germany.
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18
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Low Temperature Water-Gas Shift: Enhancing Stability through Optimizing Rb Loading on Pt/ZrO2. Catalysts 2021. [DOI: 10.3390/catal11020210] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Recent studies have shown that appropriate levels of alkali promotion can significantly improve the rate of low-temperature water gas shift (LT-WGS) on a range of catalysts. At sufficient loadings, the alkali metal can weaken the formate C–H bond and promote formate dehydrogenation, which is the proposed rate determining step in the formate associative mechanism. In a continuation of these studies, the effect of Rb promotion on Pt/ZrO2 is examined herein. Pt/ZrO2 catalysts were prepared with several different Rb loadings and characterized using temperature programmed reduction mass spectrometry (TPR-MS), temperature programmed desorption (TPD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), an X-ray absorption near edge spectroscopy (XANES) difference procedure, extended X-ray absorption fine structure spectroscopy (EXAFS) fitting, TPR-EXAFS/XANES, and reactor testing. At loadings of 2.79% Rb or higher, a significant shift was seen in the formate ν(CH) band. The results showed that a Rb loading of 4.65%, significantly improves the rate of formate decomposition in the presence of steam via weakening the formate C–H bond. However, excessive rubidium loading led to the increase in stability of a second intermediate, carbonate and inhibited hydrogen transfer reactions on Pt through surface blocking and accelerated agglomeration during catalyst activation. Optimal catalytic performance was achieved with loadings in the range of 0.55–0.93% Rb, where the catalyst maintained high activity and exhibited higher stability in comparison with the unpromoted catalyst.
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19
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Hess C. New advances in using Raman spectroscopy for the characterization of catalysts and catalytic reactions. Chem Soc Rev 2021; 50:3519-3564. [PMID: 33501926 DOI: 10.1039/d0cs01059f] [Citation(s) in RCA: 77] [Impact Index Per Article: 25.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Gaining insight into the mode of operation of heterogeneous catalysts is of great scientific and economic interest. Raman spectroscopy has proven its potential as a powerful vibrational spectroscopic technique for a fundamental and molecular-level characterization of catalysts and catalytic reactions. Raman spectra provide important insight into reaction mechanisms by revealing specific information on the catalysts' (defect) structure in the bulk and at the surface, as well as the presence of adsorbates and reaction intermediates. Modern Raman instrumentation based on single-stage spectrometers allows high throughput and versatility in design of in situ/operando cells to study working catalysts. This review highlights major advances in the use of Raman spectroscopy for the characterization of heterogeneous catalysts made during the past decade, including the development of new methods and potential directions of research for applying Raman spectroscopy to working catalysts. The main focus will be on gas-solid catalytic reactions, but (photo)catalytic reactions in the liquid phase will be touched on if it appears appropriate. The discussion begins with the main instrumentation now available for applying vibrational Raman spectroscopy to catalysis research, including in situ/operando cells for studying gas-solid catalytic processes. The focus then moves to the different types of information available from Raman spectra in the bulk and on the surface of solid catalysts, including adsorbates and surface depositions, as well as the use of theoretical calculations to facilitate band assignments and to describe (resonance) Raman effects. This is followed by a presentation of major developments in enhancing the Raman signal of heterogeneous catalysts by use of UV resonance Raman spectroscopy, surface-enhanced Raman spectroscopy (SERS), and shell-isolated nanoparticle surface-enhanced Raman spectroscopy (SHINERS). The application of time-resolved Raman studies to structural and kinetic characterization is then discussed. Finally, recent developments in spatially resolved Raman analysis of catalysts and catalytic processes are presented, including the use of coherent anti-Stokes Raman spectroscopy (CARS) and tip-enhanced Raman spectroscopy (TERS). The review concludes with an outlook on potential future developments and applications of Raman spectroscopy in heterogeneous catalysis.
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Affiliation(s)
- Christian Hess
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, Alarich-Weiss-Str. 8, 64287, Darmstadt, Germany.
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20
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Zhang L, Chang MW, Su YQ, Filot IA, Hensen EJ. A theoretical study of CO oxidation and O2 activation for transition metal overlayers on SrTiO3 perovskite. J Catal 2020. [DOI: 10.1016/j.jcat.2020.08.021] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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21
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Nelson NC, Szanyi J. Heterolytic Hydrogen Activation: Understanding Support Effects in Water–Gas Shift, Hydrodeoxygenation, and CO Oxidation Catalysis. ACS Catal 2020. [DOI: 10.1021/acscatal.0c01059] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Nicholas C. Nelson
- Institute for Integrated Catalysis, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - János Szanyi
- Institute for Integrated Catalysis, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
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22
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Schilling C, Ziemba M, Hess C, Ganduglia-Pirovano MV. Identification of single-atom active sites in CO oxidation over oxide-supported Au catalysts. J Catal 2020. [DOI: 10.1016/j.jcat.2020.01.022] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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23
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Ober P, Rogg S, Hess C. Direct Evidence for Active Support Participation in Oxide Catalysis: Multiple Operando Spectroscopy of VOx/Ceria. ACS Catal 2020. [DOI: 10.1021/acscatal.9b05174] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Patrick Ober
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, Alarich-Weiss-Str. 8, 64287 Darmstadt, Germany
| | - Simone Rogg
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, Alarich-Weiss-Str. 8, 64287 Darmstadt, Germany
| | - Christian Hess
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, Alarich-Weiss-Str. 8, 64287 Darmstadt, Germany
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24
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Murakami K, Ogo S, Ishikawa A, Takeno Y, Higo T, Tsuneki H, Nakai H, Sekine Y. Heteroatom doping effects on interaction of H 2O and CeO 2 (111) surfaces studied using density functional theory: Key roles of ionic radius and dispersion. J Chem Phys 2020; 152:014707. [PMID: 31914759 DOI: 10.1063/1.5138670] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Understanding heteroatom doping effects on the interaction between H2O and cerium oxide (ceria, CeO2) surfaces is crucially important for elucidating heterogeneous catalytic reactions of CeO2-based oxides. Surfaces of CeO2 (111) doped with quadrivalent (Ti, Zr), trivalent (Al, Ga, Sc, Y, La), or divalent (Ca, Sr, Ba) cations are investigated using density functional theory (DFT) calculations modified for onsite Coulomb interactions (DFT + U). Trivalent (except for Al) and divalent cation doping induces the formation of intrinsic oxygen vacancy (Ovac), which is backfilled easily by H2O. Partially OH-terminated surfaces are formed. Furthermore, dissociative adsorption of H2O is simulated on the OH terminated surfaces (for trivalent or divalent cation doped models) and pure surfaces (for Al and quadrivalent cation doped surfaces). The ionic radius is crucially important. In fact, H2O dissociates spontaneously on the small cations. Although a slight change is induced by doping as for the H2O adsorption energy at Ce sites, the H2O dissociative adsorption at Ce sites is well-assisted by dopants with a smaller ionic radius. In terms of the amount of promoted Ce sites, the arrangement of dopant sites is also fundamentally important.
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Affiliation(s)
- Kota Murakami
- Applied Chemistry, Waseda University, 3-4-1, Okubo, Shinjuku, Tokyo 169-8555, Japan
| | - Shuhei Ogo
- Applied Chemistry, Waseda University, 3-4-1, Okubo, Shinjuku, Tokyo 169-8555, Japan
| | - Atsushi Ishikawa
- PRESTO, Japan Science and Technology Agency (JST), 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
| | - Yuna Takeno
- Applied Chemistry, Waseda University, 3-4-1, Okubo, Shinjuku, Tokyo 169-8555, Japan
| | - Takuma Higo
- Applied Chemistry, Waseda University, 3-4-1, Okubo, Shinjuku, Tokyo 169-8555, Japan
| | - Hideaki Tsuneki
- Applied Chemistry, Waseda University, 3-4-1, Okubo, Shinjuku, Tokyo 169-8555, Japan
| | - Hiromi Nakai
- Chemistry and Biochemistry, Waseda University, 3-4-1, Okubo, Shinjuku, Tokyo 169-8555, Japan
| | - Yasushi Sekine
- Applied Chemistry, Waseda University, 3-4-1, Okubo, Shinjuku, Tokyo 169-8555, Japan
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25
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Ziemba M, Hess C. Influence of gold on the reactivity behaviour of ceria nanorods in CO oxidation: combining operando spectroscopies and DFT calculations. Catal Sci Technol 2020. [DOI: 10.1039/d0cy00392a] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
In this combined Raman/UV-Vis and DFT study, structure-activity relations for CO oxidation over ceria nanorods (with/without gold) with CeO2(110) and CeO2(100) termination are elucidated using ceria nanocubes with CeO2(100) termination as reference.
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Affiliation(s)
- Marc Ziemba
- Eduard Zintl Institute of Inorganic and Physical Chemistry
- Technical University of Darmstadt
- 64287 Darmstadt
- Germany
| | - Christian Hess
- Eduard Zintl Institute of Inorganic and Physical Chemistry
- Technical University of Darmstadt
- 64287 Darmstadt
- Germany
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26
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Yuan K, Zhang YW. Engineering well-defined rare earth oxide-based nanostructures for catalyzing C1 chemical reactions. Inorg Chem Front 2020. [DOI: 10.1039/d0qi00750a] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
In this review, we summarize the nanostructural engineering and applications of rare earth oxide-based nanomaterials with well-defined compositions, crystal phases and shapes for efficiently catalyzing C1 chemical reactions.
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Affiliation(s)
- Kun Yuan
- Beijing National Laboratory for Molecular Sciences
- State Key Laboratory of Rare Earth Materials Chemistry and Applications
- PKU-HKU Joint Laboratory in Rare Earth Materials and Bioinorganic Chemistry
- College of Chemistry and Molecular Engineering
- Peking University
| | - Ya-Wen Zhang
- Beijing National Laboratory for Molecular Sciences
- State Key Laboratory of Rare Earth Materials Chemistry and Applications
- PKU-HKU Joint Laboratory in Rare Earth Materials and Bioinorganic Chemistry
- College of Chemistry and Molecular Engineering
- Peking University
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27
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Liu N, Yin P, Xu M, Yang Y, Zhang S, Zhang J, Meng X, Zhang J, Yu J, Man Y, Zhang X, Wei M. The catalytic mechanism of the Au@TiO 2−x/ZnO catalyst towards a low-temperature water-gas shift reaction. Catal Sci Technol 2020. [DOI: 10.1039/c9cy02077b] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
A redox mechanism towards the water-gas shift reaction was certified based on in situ/operando experiments and density functional theory calculation studies.
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Affiliation(s)
- Ning Liu
- State Key Laboratory of Chemical Resource Engineering, Beijing Advanced Innovation Center for Soft Matter Science and Engineering
- Beijing University of Chemical Technology
- Beijing 100029
- P. R. China
| | - Pan Yin
- State Key Laboratory of Chemical Resource Engineering, Beijing Advanced Innovation Center for Soft Matter Science and Engineering
- Beijing University of Chemical Technology
- Beijing 100029
- P. R. China
| | - Ming Xu
- College of Chemistry and Molecular Engineering and College of Engineering, BIC-ESAT
- Peking University
- Beijing 100871
- P. R. China
| | - Yusen Yang
- State Key Laboratory of Chemical Resource Engineering, Beijing Advanced Innovation Center for Soft Matter Science and Engineering
- Beijing University of Chemical Technology
- Beijing 100029
- P. R. China
| | - Shaomin Zhang
- State Key Laboratory of Chemical Resource Engineering, Beijing Advanced Innovation Center for Soft Matter Science and Engineering
- Beijing University of Chemical Technology
- Beijing 100029
- P. R. China
| | - Junbo Zhang
- State Key Laboratory of Chemical Resource Engineering, Beijing Advanced Innovation Center for Soft Matter Science and Engineering
- Beijing University of Chemical Technology
- Beijing 100029
- P. R. China
| | - Xiaoyu Meng
- State Key Laboratory of Chemical Resource Engineering, Beijing Advanced Innovation Center for Soft Matter Science and Engineering
- Beijing University of Chemical Technology
- Beijing 100029
- P. R. China
| | - Jian Zhang
- State Key Laboratory of Chemical Resource Engineering, Beijing Advanced Innovation Center for Soft Matter Science and Engineering
- Beijing University of Chemical Technology
- Beijing 100029
- P. R. China
| | - Jun Yu
- State Key Laboratory of Chemical Resource Engineering, Beijing Advanced Innovation Center for Soft Matter Science and Engineering
- Beijing University of Chemical Technology
- Beijing 100029
- P. R. China
| | - Yi Man
- Beijing Research Institute of Chemical Industry
- Sinopec Group
- Beijing 100013
- P. R. China
| | - Xin Zhang
- State Key Laboratory of Chemical Resource Engineering, Beijing Advanced Innovation Center for Soft Matter Science and Engineering
- Beijing University of Chemical Technology
- Beijing 100029
- P. R. China
| | - Min Wei
- State Key Laboratory of Chemical Resource Engineering, Beijing Advanced Innovation Center for Soft Matter Science and Engineering
- Beijing University of Chemical Technology
- Beijing 100029
- P. R. China
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28
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Carboxyl intermediate formation via an in situ-generated metastable active site during water-gas shift catalysis. Nat Catal 2019. [DOI: 10.1038/s41929-019-0343-2] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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29
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Chemical and Electronic Changes of the CeO2 Support during CO Oxidation on Au/CeO2 Catalysts: Time-Resolved Operando XAS at the Ce LIII Edge. Catalysts 2019. [DOI: 10.3390/catal9100785] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
While being highly active for the CO oxidation reaction already at low temperatures, Au/CeO2 catalysts suffer from continuous deactivation with time on stream, with the activity and deactivation depending on the initial catalyst activation procedure. In previous X-ray absorption measurements at the Au LIII edge, which focused on changes in the electronic and geometric changes of Au, we found a modest increase of the Au particle size during reaction, with the Au nanoparticles (NPs) present in a dominantly metallic state during reaction, regardless of the pretreatment. Here we aim at expanding on these insights by examining the changes in electronic and chemical composition of the CeO2 support induced by different pretreatment procedures and during subsequent CO oxidation at 80 °C, by following changes at the Ce LIII near edge region in time-resolved operando X-ray absorption measurements. The results indicate a strong dependence of the initial concentration of Ce3+ ions on the pretreatment, while during subsequent reaction this rapidly approaches a steady-state value which depends on the oxidative/reductive character of the reaction gas mixture, but is largely independent of the pretreatment. These results are discussed and related to earlier finding on the electronic properties of Au nanoparticles under identical reaction conditions.
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30
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Li D, Li Y, Liu X, Guo Y, Pao CW, Chen JL, Hu Y, Wang Y. NiAl2O4 Spinel Supported Pt Catalyst: High Performance and Origin in Aqueous-Phase Reforming of Methanol. ACS Catal 2019. [DOI: 10.1021/acscatal.9b02243] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Didi Li
- Shanghai Key Laboratory of Functional Materials Chemistry and Research Institute of Industrial Catalysis, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Meilong Road 130, Shanghai 200237, P. R. China
| | - Yi Li
- School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, P. R. China
| | - Xiaohui Liu
- Shanghai Key Laboratory of Functional Materials Chemistry and Research Institute of Industrial Catalysis, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Meilong Road 130, Shanghai 200237, P. R. China
| | - Yong Guo
- Shanghai Key Laboratory of Functional Materials Chemistry and Research Institute of Industrial Catalysis, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Meilong Road 130, Shanghai 200237, P. R. China
| | - Chih-Wen Pao
- National Synchrotron Radiation Research Centre, Hsinchu 30076, Taiwan
| | - Jeng-Lung Chen
- National Synchrotron Radiation Research Centre, Hsinchu 30076, Taiwan
| | - Yongfeng Hu
- Canadian Light Source Inc., 44 Innovation Boulevard, Saskatoon, Saskatchewan S7N 2V3, Canada
| | - Yanqin Wang
- Shanghai Key Laboratory of Functional Materials Chemistry and Research Institute of Industrial Catalysis, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Meilong Road 130, Shanghai 200237, P. R. China
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31
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Insights into the Pyrolysis Processes of Ce-MOFs for Preparing Highly Active Catalysts of Toluene Combustion. Catalysts 2019. [DOI: 10.3390/catal9080682] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Metal organic frameworks (MOFs) have recently been used as precursors of the catalysts for the combustion of volatile organic compounds (VOCs). In the present work, three kinds of CeO2 catalysts were successfully synthesized from Ce-MOF-808, Ce-BTC, and Ce-UiO-66, with specific topological structures and coordinate environments. Catalysts with small particle size, stacking mode, and structural defects could be created by pyrolysis of Ce-MOFs, which affects the activity in the toluene combustion significantly. Raman spectra, XPS, and OSC studies were performed to reveal the formation of defect sites. The thermal redox properties were determined by H2-TPR. Catalytic activity tests were conducted on the toluene combustion, and CeO2-MOF-808 showed the best catalytic performance (T90 = 278 °C) due to its having the largest specific surface area, abundant active surface oxygen species, and low-temperature reducibility.
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32
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Tabakova T. Recent Advances in Design of Gold-Based Catalysts for H 2 Clean-Up Reactions. Front Chem 2019; 7:517. [PMID: 31448254 PMCID: PMC6692441 DOI: 10.3389/fchem.2019.00517] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Accepted: 07/05/2019] [Indexed: 11/13/2022] Open
Abstract
Over the past three decades, supported gold nanoparticles have demonstrated outstanding properties and continue to attract the interest of the scientific community. Several books and comprehensive reviews as well as numerous papers cover a variety of fundamental and applied aspects specific to gold-based catalyst synthesis, characterization by different techniques, relationship among catalyst support features, electronic and structural properties of gold particles, and catalytic activity, reaction mechanism, and theoretical modeling. Among the Au-catalyzed reactions targeting environmental protection and sustainable energy applications, particular attention is paid to pure hydrogen production. The increasing demands for high-purity hydrogen for fuel cell systems caused a renewed interest in the water-gas shift reaction. This well-known industrial process provides an attractive way for hydrogen generation and additional increase of its concentration in the gas mixtures obtained by processes utilizing coal, petroleum, or biomass resources. An effective step for further elimination of CO traces from the reformate stream after water-gas shift unit is the preferential CO oxidation. Developing highly active, stable, and selective catalysts for these two reactions is of primary importance for efficient upgrading of hydrogen purity in fuel cell applications. This review aims to extend the existing knowledge and understanding of the properties of gold-based catalysts for H2 clean-up reactions. In particular, new approaches and strategies for design of high-performing and cost-effective formulations are addressed. Emphasis is placed on efforts to explore appropriate and economically viable supports with complex composition prepared by various synthesis procedures. Relevance of ceria application as a support for new-generation WGS catalysts is pointed out. The role of the nature of support in catalyst behavior and specifically the existence of an active gold-support interface is highlighted. Long-term stability and tolerance toward start-up/shutdown cycling are discussed. Very recent advances in catalyst design are described focusing on structured catalysts and microchannel reactors. The latest mechanistic aspects of the water-gas shift reaction and preferential CO oxidation over gold-based catalysts from density functional theory calculations are noted because of their essential role in discovering novel highly efficient catalysts.
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Affiliation(s)
- Tatyana Tabakova
- Institute of Catalysis, Bulgarian Academy of Sciences, Sofia, Bulgaria
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33
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Elger AK, Baranyai J, Hofmann K, Hess C. Direct Operando Spectroscopic Observation of Oxygen Vacancies in Working Ceria-Based Gas Sensors. ACS Sens 2019; 4:1497-1501. [PMID: 31117364 DOI: 10.1021/acssensors.9b00521] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Metal-oxide semiconductors are of great interest for gas-sensing applications. We provide new insights into the mode of operation of ceria-based gas sensors during ethanol gas sensing using combined operando Raman-gas-phase FTIR spectroscopy. Visible Raman spectroscopy is employed to monitor the presence of oxygen vacancies in ceria via F2g mode softening, while simultaneously recorded FTIR spectra capture the gas-phase composition. Such an experimental approach allowing the direct observation of oxygen vacancies in metal-oxide gas sensors has not been reported in the literature. By systematically varying the gas atmosphere and temperature, we can relate the sensor response to the spectroscopic signals, enabling us to obtain new fundamental insight into the functioning of metal-oxide semiconductor gas sensors, as well as their differences from heterogeneous catalysts.
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Affiliation(s)
- Ann-Kathrin Elger
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, Alarich-Weiss-Strasse 8, 64287 Darmstadt, Germany
| | - Julian Baranyai
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, Alarich-Weiss-Strasse 8, 64287 Darmstadt, Germany
| | - Kathrin Hofmann
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, Alarich-Weiss-Strasse 8, 64287 Darmstadt, Germany
| | - Christian Hess
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, Alarich-Weiss-Strasse 8, 64287 Darmstadt, Germany
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