1
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Shen M, Rackers WH, Sadtler B. Getting the Most Out of Fluorogenic Probes: Challenges and Opportunities in Using Single-Molecule Fluorescence to Image Electro- and Photocatalysis. CHEMICAL & BIOMEDICAL IMAGING 2023; 1:692-715. [PMID: 38037609 PMCID: PMC10685636 DOI: 10.1021/cbmi.3c00075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Revised: 10/04/2023] [Accepted: 10/07/2023] [Indexed: 12/02/2023]
Abstract
Single-molecule fluorescence microscopy enables the direct observation of individual reaction events at the surface of a catalyst. It has become a powerful tool to image in real time both intra- and interparticle heterogeneity among different nanoscale catalyst particles. Single-molecule fluorescence microscopy of heterogeneous catalysts relies on the detection of chemically activated fluorogenic probes that are converted from a nonfluorescent state into a highly fluorescent state through a reaction mediated at the catalyst surface. This review article describes challenges and opportunities in using such fluorogenic probes as proxies to develop structure-activity relationships in nanoscale electrocatalysts and photocatalysts. We compare single-molecule fluorescence microscopy to other microscopies for imaging catalysis in situ to highlight the distinct advantages and limitations of this technique. We describe correlative imaging between super-resolution activity maps obtained from multiple fluorogenic probes to understand the chemical origins behind spatial variations in activity that are frequently observed for nanoscale catalysts. Fluorogenic probes, originally developed for biological imaging, are introduced that can detect products such as carbon monoxide, nitrite, and ammonia, which are generated by electro- and photocatalysts for fuel production and environmental remediation. We conclude by describing how single-molecule imaging can provide mechanistic insights for a broader scope of catalytic systems, such as single-atom catalysts.
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Affiliation(s)
- Meikun Shen
- Department
of Chemistry and Biochemistry, University
of Oregon, Eugene, Oregon 97403, United States
| | - William H. Rackers
- Department
of Chemistry, Washington University, St. Louis, Missouri 63130, United States
| | - Bryce Sadtler
- Department
of Chemistry, Washington University, St. Louis, Missouri 63130, United States
- Institute
of Materials Science & Engineering, Washington University, St. Louis, Missouri 63130, United States
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2
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Zhang C, Eraky H, Tan S, Hitchcock A, Higgins D. In Situ Studies of Copper-Based CO 2 Reduction Electrocatalysts by Scanning Transmission Soft X-ray Microscopy. ACS NANO 2023; 17:21337-21348. [PMID: 37906612 DOI: 10.1021/acsnano.3c05964] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/02/2023]
Abstract
A microfluidic-enabled electrochemical device has been developed to investigate electrochemically active nanomaterials under reaction conditions using in situ scanning transmission soft X-ray microscopy (STXM). In situ STXM measurements were conducted on electrodeposited Cu catalysts under electrochemical CO2 reduction (CO2R) conditions. The study provides detailed, quantitative results about the changes in the morphology and chemical structure of the catalytic nanoparticles as a function of applied potentials. The deposited Cu nanoparticles initially contain both Cu(0) and Cu(I). As an increasingly cathodic potential is applied, the Cu(I) species gradually convert to Cu(0) over the potential range of +0.4 to 0 V versus the reversible hydrogen electrode (VRHE). During this process, Cu(I) particles of various sizes are converted to metallic Cu at different reaction rates and at slightly different potentials, indicating a degree of heterogeneity in the electrochemical response of discrete particles. At CO2R relevant potentials, only metallic Cu is observed, and the morphology of the particles is fairly stable within the spatial resolution limits of STXM (∼40 nm). We also report in situ STXM studies of a working electrode with relatively thick Cu-based electrodeposits. The spatially resolved chemical analysis identifies that Cu-oxide species can persist under CO2R conditions, but only when the catalytic nanoparticles are electronically isolated from the working electrode and therefore are catalytically irrelevant. In summary, in situ STXM is presented as a technique to gain advanced morphological and spatially resolved chemical structure insights into electrochemically active nanomaterials, which was used to provide improved understanding regarding Cu nanomaterial catalysts under CO2 reduction conditions.
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Affiliation(s)
- Chunyang Zhang
- Chemical Engineering, McMaster University, Hamilton, Ontario, Canada, L8S 4M1
- Chemistry & Chemical Biology, McMaster University, Hamilton, Ontario, Canada, L8S 4M1
| | - Haytham Eraky
- Chemistry & Chemical Biology, McMaster University, Hamilton, Ontario, Canada, L8S 4M1
| | - Shunquan Tan
- Chemical Engineering, McMaster University, Hamilton, Ontario, Canada, L8S 4M1
| | - Adam Hitchcock
- Chemistry & Chemical Biology, McMaster University, Hamilton, Ontario, Canada, L8S 4M1
| | - Drew Higgins
- Chemical Engineering, McMaster University, Hamilton, Ontario, Canada, L8S 4M1
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3
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Chen S, Yang B. Activity and stability of alloyed NiCo catalyst for the dry reforming of methane: A combined DFT and microkinetic modeling study. Catal Today 2022. [DOI: 10.1016/j.cattod.2021.11.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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4
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Research Progress on Magnetic Catalysts and Its Application in Hydrogen Production Area. ENERGIES 2022. [DOI: 10.3390/en15155327] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The noncontact heating technology of IH targets heat directly where it is needed through the electromagnetic energy adsorption and conversion of magnetic materials. Unlike conventional heating methods, the heat generated by electromagnetic induction of magnetic materials can be applied directly into the reactor without heating the entire device; this new heating method is not only more energy efficient but also safer, cleaner and more sustainable if renewable electricity is adopted; moreover, magnetic catalysts can be recovered and reused by separating chemical reactants and products from the catalyst by the application of a magnetic field, and it can provide the required heat source for the reaction without altering its catalytic properties. Magnetic catalysts with an electric field have been applied to some industrial areas, such as the preparation of new materials, catalytic oxidation reactions, and high-temperature heat absorption reactions. It is a trend that is used in the hydrogen production process, especially the endothermic steam reforming process. Therefore, in this paper, the heat release mechanism, properties, preparation methods and the application of magnetic catalysts were presented. Highlights of the application and performance of magnetic catalysts in the hydrogen production area were also discussed.
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5
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Rodriguez JA, Rui N, Zhang F, Senanayake SD. In Situ Studies of Methane Activation Using Synchrotron-Based Techniques: Guiding the Conversion of C–H Bonds. ACS Catal 2022. [DOI: 10.1021/acscatal.2c00941] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- José A. Rodriguez
- Chemistry Division, Brookhaven National Laboratory, Upton, New York 11973, United States
- Department of Materials Science and Chemical Engineering, SUNY at Stony Brook, Stony Brook, New York 11794, United States
| | - Ning Rui
- Chemistry Division, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - Feng Zhang
- Department of Materials Science and Chemical Engineering, SUNY at Stony Brook, Stony Brook, New York 11794, United States
| | - Sanjaya D. Senanayake
- Chemistry Division, Brookhaven National Laboratory, Upton, New York 11973, United States
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6
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Wang J, Fu Y, Kong W, Li S, Yuan C, Bai J, Chen X, Zhang J, Sun Y. Investigation of Atom-Level Reaction Kinetics of Carbon-Resistant Bimetallic NiCo-Reforming Catalysts: Combining Microkinetic Modeling and Density Functional Theory. ACS Catal 2022. [DOI: 10.1021/acscatal.2c00027] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jiyang Wang
- CAS Key Laboratory of Low-Carbon Conversion Science and Engineering, Shanghai Advanced Research Institute, Chinese Academy of Science, Shanghai 201210, P.R. China
- University of the Chinese Academy of Sciences, Beijing 100049, P.R. China
| | - Yu Fu
- CAS Key Laboratory of Low-Carbon Conversion Science and Engineering, Shanghai Advanced Research Institute, Chinese Academy of Science, Shanghai 201210, P.R. China
| | - Wenbo Kong
- CAS Key Laboratory of Low-Carbon Conversion Science and Engineering, Shanghai Advanced Research Institute, Chinese Academy of Science, Shanghai 201210, P.R. China
| | - Shuqing Li
- CAS Key Laboratory of Low-Carbon Conversion Science and Engineering, Shanghai Advanced Research Institute, Chinese Academy of Science, Shanghai 201210, P.R. China
| | - Changkun Yuan
- CAS Key Laboratory of Low-Carbon Conversion Science and Engineering, Shanghai Advanced Research Institute, Chinese Academy of Science, Shanghai 201210, P.R. China
| | - Jieru Bai
- CAS Key Laboratory of Low-Carbon Conversion Science and Engineering, Shanghai Advanced Research Institute, Chinese Academy of Science, Shanghai 201210, P.R. China
- University of the Chinese Academy of Sciences, Beijing 100049, P.R. China
| | - Xia Chen
- CAS Key Laboratory of Low-Carbon Conversion Science and Engineering, Shanghai Advanced Research Institute, Chinese Academy of Science, Shanghai 201210, P.R. China
- University of the Chinese Academy of Sciences, Beijing 100049, P.R. China
| | - Jun Zhang
- CAS Key Laboratory of Low-Carbon Conversion Science and Engineering, Shanghai Advanced Research Institute, Chinese Academy of Science, Shanghai 201210, P.R. China
| | - Yuhan Sun
- CAS Key Laboratory of Low-Carbon Conversion Science and Engineering, Shanghai Advanced Research Institute, Chinese Academy of Science, Shanghai 201210, P.R. China
- Institute of 2060, ShanghaiTech University, Shanghai 201203, P.R. China
- Shanghai Institute of Clean Technology, Shanghai 201620, P.R. China
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7
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Abstract
Clean biogas, produced by anaerobic digestion of biomasses or organic wastes, is one of the most promising substitutes for natural gas. After its purification, it can be valorized through different reforming processes that convert CH4 and CO2 into synthesis gas (a mixture of CO and H2). However, these processes have many issues related to the harsh conditions of reaction used, the high carbon formation rate and the remarkable endothermicity of the reforming reactions. In this context, the use of the appropriate catalyst is of paramount importance to avoid deactivation, to deal with heat issues and mild reaction conditions and to attain an exploitable syngas composition. The development of a catalyst with high activity and stability can be achieved using different active phases, catalytic supports, promoters, preparation methods and catalyst configurations. In this paper, a review of the recent findings in biogas reforming is presented. The different elements that compose the catalytic system are systematically reviewed with particular attention on the new findings that allow to obtain catalysts with high activity, stability, and resistance towards carbon formation.
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8
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Torimoto M, Sekine Y. Effects of alloying for steam or dry reforming of methane: a review of recent studies. Catal Sci Technol 2022. [DOI: 10.1039/d2cy00066k] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A survey on the catalytic nature of Ni-based alloy catalysts in recent years provides a direction for future catalyst development.
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Affiliation(s)
- Maki Torimoto
- Applied Chemistry, 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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9
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Xiao Z, Hou F, Zhang J, Zheng Q, Xu J, Pan L, Wang L, Zou J, Zhang X, Li G. Methane Dry Reforming by Ni-Cu Nanoalloys Anchored on Periclase-Phase MgAlO x Nanosheets for Enhanced Syngas Production. ACS APPLIED MATERIALS & INTERFACES 2021; 13:48838-48854. [PMID: 34613699 DOI: 10.1021/acsami.1c14918] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Stable and efficient syngas production via methane dry reforming is highly desirable as it utilizes two greenhouse gases simultaneously. In this work, active Ni-Cu nanoalloys stably anchored on periclase-phase MgAlOx nanosheets were successfully synthesized by a hydrothermal method. These highly dispersed small Ni-Cu alloys strongly interacted with the periclase-phase MgAlOx nanosheets, on which abundant base sites were accessible. On the optimal catalyst (6Ni6CuMgAl-S), methane and carbon dioxide conversion always reached 85 and 90% at 700 °C under a gas hour speed velocity of 40,000 mL/gcat h for more than 70 h. The hydrogen production rate was maintained at 1.8 mmol/min, and the ratio of H2/CO was kept at approximately 0.96 under a CH4 and CO2 flow rate of 25 mL/min. Coke deposition and Ni sintering were effectively suppressed by the formation of a Ni-Cu alloy, the laminar structure, and the periclase phase of the MgAlOx support. Moreover, the alloy nanoparticles were reconstructed into a segregated Ni-Cu alloy structure in response to the reaction environment, and this structure was more stable and still active. Density functional theory calculations showed that carbon adsorption was inhibited on the segregated Ni-Cu alloy. Furthermore, the experimental thermogravimetric and O2-TPO results confirmed the significant decrease in carbon deposition on the Ni-Cu alloy catalysts.
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Affiliation(s)
- Zhourong Xiao
- Key Laboratory for Green Chemical Technology of Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
| | - Fang Hou
- Key Laboratory for Green Chemical Technology of Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
| | - Junjie Zhang
- Key Laboratory for Green Chemical Technology of Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
| | - Qiancheng Zheng
- Key Laboratory for Green Chemical Technology of Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
| | - Jisheng Xu
- Key Laboratory for Green Chemical Technology of Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
| | - Lun Pan
- Key Laboratory for Green Chemical Technology of Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
- Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072, China
| | - Li Wang
- Key Laboratory for Green Chemical Technology of Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
- Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072, China
| | - Jijun Zou
- Key Laboratory for Green Chemical Technology of Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
- Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072, China
| | - Xiangwen Zhang
- Key Laboratory for Green Chemical Technology of Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
- Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072, China
| | - Guozhu Li
- Key Laboratory for Green Chemical Technology of Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
- Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072, China
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10
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Zeng F, Wei B, Lan D, Ge J. Highly Dispersed Ni xGa y Catalyst and La 2O 3 Promoter Supported by LDO Nanosheets for Dry Reforming of Methane: Synergetic Catalysis by Ni, Ga, and La 2O 3. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:9744-9754. [PMID: 34348023 DOI: 10.1021/acs.langmuir.1c01162] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
A highly active and stable Ni-based catalyst is the focal point for research on dry reforming of methane (DRM). Here, NixGay/La2O3-LDO catalysts composed of highly dispersed NixGay and La2O3 nanoparticles supported by the MgO/Al2O3 layered double oxide (LDO) nanosheets were synthesized by chemical methods. According to transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), CO2-TPD, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and thermal gravitational analysis (TGA), a synergistic reaction mechanism was proposed to explain the superior performance of the Ni0.8Ga0.2/La2O3-LDO catalyst. The NixGay alloy catalyst provides an effective way to balance the speed of CH4 cracking and CO2 disassociation, and the La2O3 promoter enriched the CO2 and ensured the generation of active O in time. They worked together to inhibit carbon accumulation and significantly improve the catalyst's activity and stability.
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Affiliation(s)
- Fang Zeng
- Shanghai Key Laboratory of Green Chemistry and Chemical Processes. School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, China
| | - Bo Wei
- Shanghai Key Laboratory of Green Chemistry and Chemical Processes. School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, China
| | - Dengpeng Lan
- Shanghai Key Laboratory of Green Chemistry and Chemical Processes. School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, China
| | - Jianping Ge
- Shanghai Key Laboratory of Green Chemistry and Chemical Processes. School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, China
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11
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Kim S, Lauterbach J, Sasmaz E. Yolk–Shell Pt-NiCe@SiO 2 Single-Atom-Alloy Catalysts for Low-Temperature Dry Reforming of Methane. ACS Catal 2021. [DOI: 10.1021/acscatal.1c01223] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Sunkyu Kim
- Department of Chemical and Biomolecular Engineering, University of California, Irvine, Irvine, California 92697, United States
| | - Jochen Lauterbach
- Smartstate Center for Strategic Approaches to the Generation of Electricity (SAGE), Department of Chemical Engineering, University of South Carolina, Columbia, South Carolina 29208, United States
| | - Erdem Sasmaz
- Department of Chemical and Biomolecular Engineering, University of California, Irvine, Irvine, California 92697, United States
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12
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Castillo RG, Hahn AW, Van Kuiken BE, Henthorn JT, McGale J, DeBeer S. Probing Physical Oxidation State by Resonant X-ray Emission Spectroscopy: Applications to Iron Model Complexes and Nitrogenase. Angew Chem Int Ed Engl 2021; 60:10112-10121. [PMID: 33497500 PMCID: PMC8252016 DOI: 10.1002/anie.202015669] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Indexed: 11/07/2022]
Abstract
The ability of resonant X-ray emission spectroscopy (XES) to recover physical oxidation state information, which may often be ambiguous in conventional X-ray spectroscopy, is demonstrated. By combining Kβ XES with resonant excitation in the XAS pre-edge region, resonant Kβ XES (or 1s3p RXES) data are obtained, which probe the 3dn+1 final-state configuration. Comparison of the non-resonant and resonant XES for a series of high-spin ferrous and ferric complexes shows that oxidation state assignments that were previously unclear are now easily made. The present study spans iron tetrachlorides, iron sulfur clusters, and the MoFe protein of nitrogenase. While 1s3p RXES studies have previously been reported, to our knowledge, 1s3p RXES has not been previously utilized to resolve questions of metal valency in highly covalent systems. As such, the approach presented herein provides chemists with means to more rigorously and quantitatively address challenging electronic-structure questions.
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Affiliation(s)
- Rebeca G. Castillo
- Department of Inorganic SpectroscopyMax Planck Institute for Chemical Energy ConversionStiftstrasse 34–3645470Mülheim an der RuhrGermany
| | - Anselm W. Hahn
- Department of Inorganic SpectroscopyMax Planck Institute for Chemical Energy ConversionStiftstrasse 34–3645470Mülheim an der RuhrGermany
| | | | - Justin T. Henthorn
- Department of Inorganic SpectroscopyMax Planck Institute for Chemical Energy ConversionStiftstrasse 34–3645470Mülheim an der RuhrGermany
| | - Jeremy McGale
- Department of Inorganic SpectroscopyMax Planck Institute for Chemical Energy ConversionStiftstrasse 34–3645470Mülheim an der RuhrGermany
| | - Serena DeBeer
- Department of Inorganic SpectroscopyMax Planck Institute for Chemical Energy ConversionStiftstrasse 34–3645470Mülheim an der RuhrGermany
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13
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Castillo RG, Hahn AW, Van Kuiken BE, Henthorn JT, McGale J, DeBeer S. Probing Physical Oxidation State by Resonant X‐ray Emission Spectroscopy: Applications to Iron Model Complexes and Nitrogenase. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202015669] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Rebeca G. Castillo
- Department of Inorganic Spectroscopy Max Planck Institute for Chemical Energy Conversion Stiftstrasse 34–36 45470 Mülheim an der Ruhr Germany
| | - Anselm W. Hahn
- Department of Inorganic Spectroscopy Max Planck Institute for Chemical Energy Conversion Stiftstrasse 34–36 45470 Mülheim an der Ruhr Germany
| | | | - Justin T. Henthorn
- Department of Inorganic Spectroscopy Max Planck Institute for Chemical Energy Conversion Stiftstrasse 34–36 45470 Mülheim an der Ruhr Germany
| | - Jeremy McGale
- Department of Inorganic Spectroscopy Max Planck Institute for Chemical Energy Conversion Stiftstrasse 34–36 45470 Mülheim an der Ruhr Germany
| | - Serena DeBeer
- Department of Inorganic Spectroscopy Max Planck Institute for Chemical Energy Conversion Stiftstrasse 34–36 45470 Mülheim an der Ruhr Germany
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14
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Beheshti Askari A, Al Samarai M, Hiraoka N, Ishii H, Tillmann L, Muhler M, DeBeer S. In situ X-ray emission and high-resolution X-ray absorption spectroscopy applied to Ni-based bimetallic dry methane reforming catalysts. NANOSCALE 2020; 12:15185-15192. [PMID: 32657291 DOI: 10.1039/d0nr01960g] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The promoting effect of cobalt on the catalytic activity of a NiCoO Dry Methane Reforming (DMR) catalyst was studied by a combination of in situ Kβ X-ray Emission Spectroscopy (XES) and Kβ-detected High Energy Resolution Fluorescence Detected X-ray absorption spectroscopy (HERFD XAS). Following the calcination process, Ni XES and Kβ-detected HERFD XAS data revealed that the NiO coordination in the NiCoO catalyst has a higher degree of symmetry and is different than that of pure NiO/γ-Al2O3. Following the reductive activation, it was found that the NiCoO/γ-Al2O3 catalyst required a relatively higher temperature compared to the monometallic NiO/γ-Al2O3 catalyst. This finding suggests that Co is hampering the reduction of Ni in the NiCoO catalyst by modulation of its electronic structure. It has also been previously shown that the addition of Co enhances the DMR activity. Further, the Kβ XES spectrum of the partly reduced catalysts at 450 °C reveals that the Ni sites in the NiCoO catalyst are electronically different from the NiO catalyst. The in situ X-ray spectroscopic study demonstrates that reduced metallic Co and Ni are the primary species present after reduction and are preserved under DMR conditions. However, the NiCo catalyst appears to always be somewhat more oxidized than the Ni-only species, suggesting that the presence of cobalt modulates the Ni electronic structure. The electronic structural modulations resulting from the presence of Co may be the key to the increased activity of the NiCo catalyst relative to the Ni-only catalyst. This study emphasizes the potential of in situ X-ray spectroscopy experiments for probing the electronic structure of catalytic materials during activation and under operating conditions.
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Affiliation(s)
- Abbas Beheshti Askari
- Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, D-45470 Mülheim an der Ruhr, Germany.
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