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Liu Y, Koo K, Mao Z, Fu X, Hu X, Dravid VP. Unraveling the adsorption-limited hydrogen oxidation reaction at palladium surface via in situ electron microscopy. Proc Natl Acad Sci U S A 2024; 121:e2408277121. [PMID: 39331411 DOI: 10.1073/pnas.2408277121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2024] [Accepted: 08/16/2024] [Indexed: 09/28/2024] Open
Abstract
Palladium (Pd) catalysts have been extensively studied for the direct synthesis of H2O through the hydrogen oxidation reaction at ambient conditions. This heterogeneous catalytic reaction not only holds considerable practical significance but also serves as a classical model for investigating fundamental mechanisms, including adsorption and reactions between adsorbates. Nonetheless, the governing mechanisms and kinetics of its intermediate reaction stages under varying gas conditions remain elusive. This is attributed to the intricate interplay between adsorption, atomic diffusion, and concurrent phase transformation of catalyst. Herein, the Pd-catalyzed, water-forming hydrogen oxidation is studied in situ, to investigate intermediate reaction stages via gas cell transmission electron microscopy. The dynamic behaviors of water generation, associated with reversible palladium hydride formation, are captured in real time with a nanoscale spatial resolution. Our findings suggest that the hydrogen oxidation rate catalyzed by Pd is significantly affected by the sequence in which gases are introduced. Through direct evidence of electron diffraction and density functional theory calculation, we demonstrate that the hydrogen oxidation rate is limited by precursors' adsorption. These nanoscale insights help identify the optimal reaction conditions for Pd-catalyzed hydrogen oxidation, which has substantial implications for water production technologies. The developed understanding also advocates a broader exploration of analogous mechanisms in other metal-catalyzed reactions.
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Affiliation(s)
- Yukun Liu
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208
- International Institute of Nanotechnology, Northwestern University, Evanston, IL 60208
| | - Kunmo Koo
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208
- The Northwestern University Atomic and Nanoscale Characterization Experimental (NUANCE) Center, Northwestern University, Evanston, IL 60208
| | - Zugang Mao
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208
| | - Xianbiao Fu
- Department of Physics, Technical University of Denmark, Kongens Lyngby 2800, Denmark
| | - Xiaobing Hu
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208
- The Northwestern University Atomic and Nanoscale Characterization Experimental (NUANCE) Center, Northwestern University, Evanston, IL 60208
| | - Vinayak P Dravid
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208
- International Institute of Nanotechnology, Northwestern University, Evanston, IL 60208
- The Northwestern University Atomic and Nanoscale Characterization Experimental (NUANCE) Center, Northwestern University, Evanston, IL 60208
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Khouchaf L, Boulahya K, Das PP, Nicolopoulos S, Kis VK, Lábár JL. Study of the Microstructure of Amorphous Silica Nanostructures Using High-Resolution Electron Microscopy, Electron Energy Loss Spectroscopy, X-ray Powder Diffraction, and Electron Pair Distribution Function. MATERIALS 2020; 13:ma13194393. [PMID: 33019776 PMCID: PMC7579662 DOI: 10.3390/ma13194393] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Revised: 09/22/2020] [Accepted: 09/27/2020] [Indexed: 11/25/2022]
Abstract
Silica has many industrial (i.e., glass formers) and scientific applications. The understanding and prediction of the interesting properties of such materials are dependent on the knowledge of detailed atomic structures. In this work, amorphous silica subjected to an accelerated alkali silica reaction (ASR) was recorded at different time intervals so as to follow the evolution of the structure by means of high-resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS), and electron pair distribution function (e-PDF), combined with X-ray powder diffraction (XRPD). An increase in the size of the amorphous silica nanostructures and nanopores was observed by HRTEM, which was accompanied by the possible formation of Si–OH surface species. All of the studied samples were found to be amorphous, as observed by HRTEM, a fact that was also confirmed by XRPD and e-PDF analysis. A broad diffuse peak observed in the XRPD pattern showed a shift toward higher angles following the higher reaction times of the ASR-treated material. A comparison of the EELS spectra revealed varying spectral features in the peak edges with different reaction times due to the interaction evolution between oxygen and the silicon and OH ions. Solid-state nuclear magnetic resonance (NMR) was also used to elucidate the silica nanostructures.
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Affiliation(s)
- Lahcen Khouchaf
- École Nationale Supérieure des Mines-Télécom de Lille-Douai Lille Douai, Lille Université, CEDEX, 59653 Villeneuve D’Ascq, France;
| | - Khalid Boulahya
- Departamento de Química Inorgánica, Facultad de Qúimicas, Universidad Complutense, 28040 Madrid, Spain;
| | - Partha Pratim Das
- Electron Crystallography Solutions SL, Calle Orense 8, 28020 Madrid, Spain
- NanoMEGAS SPRL, Blvd Edmond Machtens 79, B-1080 Brussels, Belgium
- Correspondence: (P.P.D.); (S.N.)
| | - Stavros Nicolopoulos
- NanoMEGAS SPRL, Blvd Edmond Machtens 79, B-1080 Brussels, Belgium
- Correspondence: (P.P.D.); (S.N.)
| | - Viktória Kovács Kis
- Institute of Technical Physics and Materials Science, Centre for Energy Research, 1121 Budapest, Hungary; (V.K.K.); (J.L.L.)
| | - János L. Lábár
- Institute of Technical Physics and Materials Science, Centre for Energy Research, 1121 Budapest, Hungary; (V.K.K.); (J.L.L.)
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Lampert F, Kadkhodazadeh S, Kasama T, Dahl KV, Christiansen AB, Møller P. Probing the Chemistry of Adhesion between a 316L Substrate and Spin-on-Glass Coating. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:3170-3176. [PMID: 29457980 DOI: 10.1021/acs.langmuir.7b03131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Hydrogen silsesquioxane ([HSiO3/2] n)-based "spin-on-glass" has been deposited on a 316L substrate and cured in Ar/H2 gas atmosphere at 600 °C to form a continuous surface coating with submicrometer thickness. The coating functionality depends primarily on the adhesion to the substrate, which is largely affected by the chemical interaction at the interface between the coating and the substrate. We have investigated this interface by transmission electron microscopy and electron energy loss spectroscopy. The analysis identified a 5-10 nm thick interaction zone containing signals from O, Si, Cr, and Fe. Analysis of the energy loss near edge structure of the present elements identified predominantly signal from [SiO4]4- units together with Fe2+, Cr2+, and traces of Cr3+. High-resolution transmission electron microscopy images of the interface region confirm a crystalline Fe2SiO4 interfacial region. In agreement with computational thermodynamics, it is proposed that the spin-on-glass forms a chemically bonded silicate-rich interaction zone with the substrate. It was further suggested that this zone is composed of a corundum-type oxide at the substrate surface, followed by an olivine-structure intermediate phase and a spinel-type oxide in the outer regions of the interfacial zone.
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Affiliation(s)
- Felix Lampert
- Department of Mechanical Engineering , Technical University of Denmark , Produktionstorvet 425 , 2800 Kgs. Lyngby , Denmark
| | - Shima Kadkhodazadeh
- Center for Electron Nanoscopy (CEN) , Technical University of Denmark , Fysikvej 307 , 2800 Kgs. Lyngby , Denmark
| | - Takeshi Kasama
- Center for Electron Nanoscopy (CEN) , Technical University of Denmark , Fysikvej 307 , 2800 Kgs. Lyngby , Denmark
| | - Kristian Vinter Dahl
- Department of Mechanical Engineering , Technical University of Denmark , Produktionstorvet 425 , 2800 Kgs. Lyngby , Denmark
| | | | - Per Møller
- Department of Mechanical Engineering , Technical University of Denmark , Produktionstorvet 425 , 2800 Kgs. Lyngby , Denmark
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Mendis B, MacKenzie M, Craven A. A new analytical method for characterising the bonding environment at rough interfaces in high-k gate stacks using electron energy loss spectroscopy. Ultramicroscopy 2010; 110:105-17. [DOI: 10.1016/j.ultramic.2009.09.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2009] [Revised: 08/21/2009] [Accepted: 09/22/2009] [Indexed: 11/26/2022]
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Wu XL, Xiong SJ, Zhu J, Wang J, Shen JC, Chu PK. Identification of surface structures on 3C-SiC nanocrystals with hydrogen and hydroxyl bonding by photoluminescence. NANO LETTERS 2009; 9:4053-4060. [PMID: 19894694 DOI: 10.1021/nl902226u] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
SiC nanocrystals (NCs) exhibit unique surface chemistry and possess special properties. This provides the opportunity to design suitable surface structures by terminating the surface dangling bonds with different atoms thereby boding well for practical applications. In this article, we report the photoluminescence properties of 3C-SiC NCs in water suspensions with different pH values. Besides a blue band stemming from the quantum confinement effect, the 3C-SiC NCs show an additional photoluminescence band at 510 nm when the excitation wavelengths are longer than 350 nm. Its intensity relative to the blue band increases with the excitation wavelength. The 510 nm band appears only in acidic suspensions but not in alkaline ones. Fourier transform infrared, X-ray photoelectron spectroscopy, and X-ray absorption near-edge structure analyses clearly reveal that the 3C-SiC NCs in the water suspension have Si-H and Si-OH bonds on their surface, implying that water molecules only react with a Si-terminated surface. First-principle calculations suggest that the additional 510 nm band arises from structures induced by H(+) and OH(-) dissociated from water and attached to Si dimers on the modified (001) Si-terminated portion of the NCs. The size requirement is consistent with the observation that the 510 nm band can only be observed when the excitation wavelengths are relatively large, that is, excitation of bigger NCs.
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Affiliation(s)
- X L Wu
- National Laboratory of Solid State Microstructures, Department of Physics, Nanjing University, Nanjing 210093, People's Republic of China
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Direct observation of the site-specific valence electronic structure at SiO2/Si(111) interface. E-JOURNAL OF SURFACE SCIENCE AND NANOTECHNOLOGY 2006. [DOI: 10.1380/ejssnt.2006.280] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Stemmer S, Chen ZQ, Zhu WJ, Ma TP. Electron energy-loss spectroscopy study of thin film hafnium aluminates for novel gate dielectrics. J Microsc 2003; 210:74-9. [PMID: 12694419 DOI: 10.1046/j.1365-2818.2003.01175.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We have used conventional high-resolution transmission electron microscopy and electron energy-loss spectroscopy (EELS) in scanning transmission electron microscopy to investigate the microstructure and electronic structure of hafnia-based thin films doped with small amounts (6.8 at.%) of Al grown on (001) Si. The as-deposited film is amorphous with a very thin (approximately 0.5 nm) interfacial SiOx layer. The film partially crystallizes after annealing at 700 degrees C and the interfacial SiO2-like layer increases in thickness by oxygen diffusion through the Hf-aluminate layer and oxidation of the silicon substrate. Oxygen K-edge EELS fine-structures are analysed for both films and interpreted in the context of the films' microstructure. We also discuss valence electron energy-loss spectra of these ultrathin films.
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Affiliation(s)
- S Stemmer
- Materials Department, University of California, Santa Barbara 93106-5050, USA.
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Neaton JB, Muller DA, Ashcroft NW. Electronic properties of the Si/SiO2 interface from first principles. PHYSICAL REVIEW LETTERS 2000; 85:1298-1301. [PMID: 10991536 DOI: 10.1103/physrevlett.85.1298] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/1999] [Indexed: 05/23/2023]
Abstract
Unoccupied oxygen p-projected densities of states, calculated from first principles in a model Si/SiO(2) interface, are found to reproduce trends in recent atomic resolution electron energy-loss spectra [D. A. Muller et al., Nature (London) 399, 758 (1999)]. The shape of the unoccupied states and the magnitude of the local energy gap are explicitly related to the number of O second neighbors of a given oxygen atom. The calculated local energy gaps of the oxide become considerably smaller within 0.5 nm of the interface, suggesting that the electronic properties do not change abruptly at the interface.
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Affiliation(s)
- JB Neaton
- Cornell Center for Materials Research and Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853-2501, USA
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Muller DA, Sorsch T, Moccio S, Baumann FH, Evans-Lutterodt K, Timp G. The electronic structure at the atomic scale of ultrathin gate oxides. Nature 1999. [DOI: 10.1038/21602] [Citation(s) in RCA: 818] [Impact Index Per Article: 32.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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