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Zimmerli NK, Rochlitz L, Checchia S, Müller CR, Copéret C, Abdala PM. Structure and Role of a Ga-Promoter in Ni-Based Catalysts for the Selective Hydrogenation of CO 2 to Methanol. JACS AU 2024; 4:237-252. [PMID: 38274252 PMCID: PMC10806875 DOI: 10.1021/jacsau.3c00677] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Revised: 12/15/2023] [Accepted: 12/15/2023] [Indexed: 01/27/2024]
Abstract
Supported, bimetallic catalysts have shown great promise for the selective hydrogenation of CO2 to methanol. In this study, we decipher the catalytically active structure of Ni-Ga-based catalysts. To this end, model Ni-Ga-based catalysts, with varying Ni:Ga ratios, were prepared by a surface organometallic chemistry approach. In situ differential pair distribution function (d-PDF) analysis revealed that catalyst activation in H2 leads to the formation of nanoparticles based on a Ni-Ga face-centered cubic (fcc) alloy along with a small quantity of GaOx. Structure refinements of the d-PDF data enabled us to determine the amount of both alloyed Ga and GaOx species. In situ X-ray absorption spectroscopy experiments confirmed the presence of alloyed Ga and GaOx and indicated that alloying with Ga affects the electronic structure of metallic Ni (viz., Niδ-). Both the Ni:Ga ratio in the alloy and the quantity of GaOx are found to minimize methanation and to determine the methanol formation rate and the resulting methanol selectivity. The highest formation rate and methanol selectivity are found for a Ni-Ga alloy having a Ni:Ga ratio of ∼75:25 along with a small quantity of oxidized Ga species (0.14 molNi-1). Furthermore, operando infrared spectroscopy experiments indicate that GaOx species play a role in the stabilization of formate surface intermediates, which are subsequently further hydrogenated to methoxy species and ultimately to methanol. Notably, operando XAS shows that alloying between Ni and Ga is maintained under reaction conditions and is key to attaining a high methanol selectivity (by minimizing CO and CH4 formation), while oxidized Ga species enhance the methanol formation rate.
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Affiliation(s)
- Nora K. Zimmerli
- Department
of Mechanical and Process Engineering, ETH
Zürich, Leonhardstrasse 21, CH 8092 Zürich, Switzerland
| | - Lukas Rochlitz
- Department
of Chemistry and Applied Biosciences, ETH
Zürich, Vladimir-Prelog-Weg 2, CH 8093 Zürich, Switzerland
| | - Stefano Checchia
- ESRF
− The European Synchrotron, 71 Avenue des Martyrs, 38000 Grenoble, France
| | - Christoph R. Müller
- Department
of Mechanical and Process Engineering, ETH
Zürich, Leonhardstrasse 21, CH 8092 Zürich, Switzerland
| | - Christophe Copéret
- Department
of Chemistry and Applied Biosciences, ETH
Zürich, Vladimir-Prelog-Weg 2, CH 8093 Zürich, Switzerland
| | - Paula M. Abdala
- Department
of Mechanical and Process Engineering, ETH
Zürich, Leonhardstrasse 21, CH 8092 Zürich, Switzerland
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2
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Lee SW, Subramanian A, Zamudio FB, Zhong JQ, Kozlov SM, Shaikhutdinov S, Roldan Cuenya B. Interaction of Gallium with a Copper Surface: Surface Alloying and Formation of Ordered Structures. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2023; 127:20700-20709. [PMID: 37908742 PMCID: PMC10614298 DOI: 10.1021/acs.jpcc.3c05711] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Revised: 09/28/2023] [Indexed: 11/02/2023]
Abstract
Alloys of gallium with transition metals have recently received considerable attention for their applications in microelectronics and catalysis. Here, we investigated the initial stages of the Ga-Cu alloy formation on Cu(111) and Cu(001) surfaces using scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and low energy electron diffraction (LEED). The results show that Ga atoms deposited using physical vapor deposition readily intermix with the Cu surface, leading to a random distribution of the Ga and Cu atoms within the surface layer, on both terraces and monolayer-thick islands formed thereon. However, as the Ga coverage increases, several ordered structures are formed. The (√3×√3)R30° structure is found to be thermodynamically most stable on Cu(111). This structure remains after vacuum annealing at 600 K, independent of the initial Ga coverage (varied between 0.5 and 3 monolayers), indicating a self-limited growth of the Ga-Cu alloy layer, with the rest of the Ga atoms migrating into the Cu crystal. For Ga deposited on Cu(001), we observed a (1 × 5)-reconstructed surface, which has never been observed for surface alloys on Cu(001). The experimental findings were rationalized on the basis of density functional theory (DFT) calculations, which provided structural models for the most stable surface Ga-Cu alloys on Cu(111) and Cu(001). The study sheds light on the complex interaction of Ga with transition metal surfaces and the interfaces formed thereon that will aid in a better understanding of surface alloying and chemical reactions on the Ga-based alloys.
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Affiliation(s)
- Si Woo Lee
- Department
of Interface Science, Fritz Haber Institute
of the Max Plank Society, Faradayweg 4-6, Berlin 14195, Germany
| | - Arravind Subramanian
- Department
of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117585, Singapore
| | - Fernando Buendia Zamudio
- Department
of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117585, Singapore
| | - Jian Qiang Zhong
- Department
of Interface Science, Fritz Haber Institute
of the Max Plank Society, Faradayweg 4-6, Berlin 14195, Germany
| | - Sergey M. Kozlov
- Department
of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117585, Singapore
| | - Shamil Shaikhutdinov
- Department
of Interface Science, Fritz Haber Institute
of the Max Plank Society, Faradayweg 4-6, Berlin 14195, Germany
| | - Beatriz Roldan Cuenya
- Department
of Interface Science, Fritz Haber Institute
of the Max Plank Society, Faradayweg 4-6, Berlin 14195, Germany
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Lee SW, Luna ML, Berdunov N, Wan W, Kunze S, Shaikhutdinov S, Cuenya BR. Unraveling surface structures of gallium promoted transition metal catalysts in CO 2 hydrogenation. Nat Commun 2023; 14:4649. [PMID: 37532720 PMCID: PMC10397205 DOI: 10.1038/s41467-023-40361-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Accepted: 07/20/2023] [Indexed: 08/04/2023] Open
Abstract
Gallium-containing alloys have recently been reported to hydrogenate CO2 to methanol at ambient pressures. However, a full understanding of the Ga-promoted catalysts is still missing due to the lack of information about the surface structures formed under reaction conditions. Here, we employed near ambient pressure scanning tunneling microscopy and x-ray photoelectron spectroscopy to monitor the evolution of well-defined Cu-Ga surfaces during CO2 hydrogenation. We show the formation of two-dimensional Ga(III) oxide islands embedded into the Cu surface in the reaction atmosphere. The islands are a few atomic layers in thickness and considerably differ from bulk Ga2O3 polymorphs. Such a complex structure, which could not be determined with conventional characterization methods on powder catalysts, should be used for elucidating the reaction mechanism on the Ga-promoted metal catalysts.
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Affiliation(s)
- Si Woo Lee
- Department of Interface Science, Fritz Haber Institute of the Max Planck Society, 14195, Berlin, Germany
| | - Mauricio Lopez Luna
- Department of Interface Science, Fritz Haber Institute of the Max Planck Society, 14195, Berlin, Germany
| | - Nikolay Berdunov
- Department of Interface Science, Fritz Haber Institute of the Max Planck Society, 14195, Berlin, Germany
| | - Weiming Wan
- Department of Interface Science, Fritz Haber Institute of the Max Planck Society, 14195, Berlin, Germany
| | - Sebastian Kunze
- Department of Interface Science, Fritz Haber Institute of the Max Planck Society, 14195, Berlin, Germany
| | - Shamil Shaikhutdinov
- Department of Interface Science, Fritz Haber Institute of the Max Planck Society, 14195, Berlin, Germany.
| | - Beatriz Roldan Cuenya
- Department of Interface Science, Fritz Haber Institute of the Max Planck Society, 14195, Berlin, Germany
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4
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Timoshenko J, Haase FT, Saddeler S, Rüscher M, Jeon HS, Herzog A, Hejral U, Bergmann A, Schulz S, Roldan Cuenya B. Deciphering the Structural and Chemical Transformations of Oxide Catalysts during Oxygen Evolution Reaction Using Quick X-ray Absorption Spectroscopy and Machine Learning. J Am Chem Soc 2023; 145:4065-4080. [PMID: 36762901 PMCID: PMC9951215 DOI: 10.1021/jacs.2c11824] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Indexed: 02/11/2023]
Abstract
Bimetallic transition-metal oxides, such as spinel-like CoxFe3-xO4 materials, are known as attractive catalysts for the oxygen evolution reaction (OER) in alkaline electrolytes. Nonetheless, unveiling the real active species and active states in these catalysts remains a challenge. The coexistence of metal ions in different chemical states and in different chemical environments, including disordered X-ray amorphous phases that all evolve under reaction conditions, hinders the application of common operando techniques. Here, we address this issue by relying on operando quick X-ray absorption fine structure spectroscopy, coupled with unsupervised and supervised machine learning methods. We use principal component analysis to understand the subtle changes in the X-ray absorption near-edge structure spectra and develop an artificial neural network to decipher the extended X-ray absorption fine structure spectra. This allows us to separately track the evolution of tetrahedrally and octahedrally coordinated species and to disentangle the chemical changes and several phase transitions taking place in CoxFe3-xO4 catalysts and on their active surface, related to the conversion of disordered oxides into spinel-like structures, transformation of spinels into active oxyhydroxides, and changes in the degree of spinel inversion in the course of the activation treatment and under OER conditions. By correlating the revealed structural changes with the distinct catalytic activity for a series of CoxFe3-xO4 samples, we elucidate the active species and OER mechanism.
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Affiliation(s)
- Janis Timoshenko
- Department
of Interface Science, Fritz-Haber Institute
of the Max-Planck Society, 14195 Berlin, Germany
| | - Felix T. Haase
- Department
of Interface Science, Fritz-Haber Institute
of the Max-Planck Society, 14195 Berlin, Germany
| | - Sascha Saddeler
- Institute
of Inorganic Chemistry and Center for Nanointegration Duisburg-Essen
(CENIDE), University of Duisburg-Essen, 45117 Essen, Germany
| | - Martina Rüscher
- Department
of Interface Science, Fritz-Haber Institute
of the Max-Planck Society, 14195 Berlin, Germany
| | - Hyo Sang Jeon
- Department
of Interface Science, Fritz-Haber Institute
of the Max-Planck Society, 14195 Berlin, Germany
| | - Antonia Herzog
- Department
of Interface Science, Fritz-Haber Institute
of the Max-Planck Society, 14195 Berlin, Germany
| | - Uta Hejral
- Department
of Interface Science, Fritz-Haber Institute
of the Max-Planck Society, 14195 Berlin, Germany
| | - Arno Bergmann
- Department
of Interface Science, Fritz-Haber Institute
of the Max-Planck Society, 14195 Berlin, Germany
| | - Stephan Schulz
- Institute
of Inorganic Chemistry and Center for Nanointegration Duisburg-Essen
(CENIDE), University of Duisburg-Essen, 45117 Essen, Germany
| | - Beatriz Roldan Cuenya
- Department
of Interface Science, Fritz-Haber Institute
of the Max-Planck Society, 14195 Berlin, Germany
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Rüscher M, Herzog A, Timoshenko J, Jeon HS, Frandsen W, Kühl S, Roldan Cuenya B. Tracking heterogeneous structural motifs and the redox behaviour of copper-zinc nanocatalysts for the electrocatalytic CO 2 reduction using operando time resolved spectroscopy and machine learning. Catal Sci Technol 2022; 12:3028-3043. [PMID: 35662799 PMCID: PMC9089751 DOI: 10.1039/d2cy00227b] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Accepted: 03/10/2022] [Indexed: 01/23/2023]
Abstract
Copper-based catalysts are established catalytic systems for the electrocatalytic CO2 reduction reaction (CO2RR), where the greenhouse gas CO2 is converted into valuable industrial chemicals, such as energy-dense C2+ products, using energy from renewable sources. However, better control over the catalyst selectivity, especially at industrially relevant high current density conditions, is needed to expedite the economic viability of the CO2RR. For this purpose, bimetallic materials, where copper is combined with a secondary metal, comprise a promising and a highly tunable catalyst for the CO2RR. Nevertheless, the synergy between copper and the selected secondary metal species, the evolution of the bimetallic structural motifs under working conditions and the effect of the secondary metal on the kinetics of the Cu redox behavior require careful investigation. Here, we employ operando quick X-ray absorption fine structure (QXAFS) spectroscopy coupled with machine-learning based data analysis and surface-enhanced Raman spectroscopy (SERS) to investigate the time-dependent chemical and structural changes in catalysts derived from shape-selected ZnO/Cu2O nanocubes under CO2RR conditions at current densities up to −500 mA cm−2. We furthermore relate the catalyst transformations observed under working conditions to the catalytic activity and selectivity and correlate potential-dependent surface and subsurface processes. We report that the addition of Zn to a Cu-based catalyst has a crucial impact on the kinetics of subsurface processes, while redox processes of the Cu surface layer remain largely unaffected. Interestingly, the presence of Zn was found to contribute to the stabilization of cationic Cu(i) species, which is of catalytic relevance since Cu(0)/Cu(i) interfaces have been reported to be beneficial for efficient electrocatalytic CO2 conversion to complex multicarbon products. At the same time, we attribute the increase of the C2+ product selectivity to the formation of Cu-rich CuZn alloys in samples with low Zn content, while Zn-rich alloy phases result in an increased formation of CO paralleled by an increase of the parasitic hydrogen evolution reaction. Elucidating the role of Zn in bimetallic CuZn nanocatalysts for the electrocatalytic CO2 reduction reaction (CO2RR), where the greenhouse gas CO2 is converted into valuable industrial chemicals using energy from renewable sources.![]()
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Affiliation(s)
- Martina Rüscher
- Department of Interface Science, Fritz-Haber Institute of the Max-Planck Society 14195 Berlin Germany
| | - Antonia Herzog
- Department of Interface Science, Fritz-Haber Institute of the Max-Planck Society 14195 Berlin Germany
| | - Janis Timoshenko
- Department of Interface Science, Fritz-Haber Institute of the Max-Planck Society 14195 Berlin Germany
| | - Hyo Sang Jeon
- Department of Interface Science, Fritz-Haber Institute of the Max-Planck Society 14195 Berlin Germany
| | - Wiebke Frandsen
- Department of Interface Science, Fritz-Haber Institute of the Max-Planck Society 14195 Berlin Germany
| | - Stefanie Kühl
- Department of Interface Science, Fritz-Haber Institute of the Max-Planck Society 14195 Berlin Germany
| | - Beatriz Roldan Cuenya
- Department of Interface Science, Fritz-Haber Institute of the Max-Planck Society 14195 Berlin Germany
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