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Wagner J, Grabnic T, Sibener SJ. STM Visualization of N 2 Dissociative Chemisorption on Ru(0001) at High Impinging Kinetic Energies. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2022; 126:18333-18342. [PMID: 36366757 PMCID: PMC9639351 DOI: 10.1021/acs.jpcc.2c05770] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Revised: 10/06/2022] [Indexed: 06/16/2023]
Abstract
This paper examines the reactive surface dynamics of energy- and angle-selected N2 dissociation on a clean Ru(0001) surface. Presented herein are the first STM images of highly energetic N2 dissociation on terrace sites utilizing a novel UHV instrument that combines a supersonic molecular beam with an in situ STM that is in-line with the molecular beam. Atomically resolved visualization of individual N2 dissociation events elucidates the fundamental reactive dynamics of the N2/Ru(0001) system by providing a detailed understanding of the on-surface dissociation dynamics: the distance and angle between nitrogen atoms from the same dissociated N2 molecule, site specificity and coordination of binding on terrace sites, and the local evolution of surrounding nanoscopic areas. These properties are precisely measured over a range of impinging N2 kinetic energies and angles, revealing previously unattainable information about the energy dissipation channels that govern the reactivity of the system. The experimental results presented in this paper provide insight into the fundamental N2 dissociation mechanism that, in conjunction with ongoing theoretical modeling, will help determine the role of dynamical processes such as energy transfer to surface phonons and nonadiabatic excitation of electron-hole pairs (ehps). These results will not only help uncover the underlying chemistry and physics that give rise to the unique behavior of this activated dissociative chemisorption system but also represent an exciting approach to studying reaction dynamics by pairing the angstrom-level spatiotemporal resolution of an in situ STM with nonequilibrium fluxes of reactive gases generated in a supersonic molecular beam to access highly activated chemical dynamics and observe the results of individual reaction events.
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2
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Zeinalipour-Yazdi CD, Hargreaves JSJ, Laassiri S, Catlow CRA. A comparative analysis of the mechanisms of ammonia synthesis on various catalysts using density functional theory. ROYAL SOCIETY OPEN SCIENCE 2021; 8:210952. [PMID: 34737878 PMCID: PMC8564627 DOI: 10.1098/rsos.210952] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Accepted: 09/20/2021] [Indexed: 05/30/2023]
Abstract
In this review, we present the recent progress in ammonia synthesis research using density functional theory (DFT) calculations on various industrial catalysts, metal nitrides and nano-cluster-supported catalysts. The mechanism of ammonia synthesis on the industrial Fe catalyst is generally accepted to be a dissociative mechanism. We have recently found, using DFT techniques, that on Co3Mo3N (111) surfaces, an associative mechanism in the synthesis of ammonia can offer a new low-energy pathway that was previously unknown. In particular, we have shown that metal nitrides that are also known to have high activity for ammonia synthesis can readily form nitrogen vacancies which can activate dinitrogen, thereby promoting the associative mechanism. These fundamental studies suggest that a promising route to the discovery of low-temperature ammonia synthesis catalysts will be to identify systems that proceed via the associative mechanism, which is closer to the nitrogen-fixation mechanism occurring in nitrogenases.
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Affiliation(s)
- Constantinos D. Zeinalipour-Yazdi
- School of Health, Sport and Bioscience, University of East London, Stratford Campus, Water Lane, London E15 4LZ, UK
- Department of Natural Sciences, Middlesex University, Hendon Campus, The Burroughs, London NW4 4BT, UK
| | | | - Said Laassiri
- Chemical and Biochemical Sciences, Green Process Engineering (CBS), Mohamed VI Polytechnic University, UM6P, Ben Guerir 43150, Morocco
| | - C. Richard A. Catlow
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK
- School of Chemistry, Cardiff University, Park Place, Cardiff CF 10 1AD, UK
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3
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Qi J, Gao L, Wei F, Wan Q, Lin S. Design of a High-Performance Electrocatalyst for N 2 Conversion to NH 3 by Trapping Single Metal Atoms on Stepped CeO 2. ACS APPLIED MATERIALS & INTERFACES 2019; 11:47525-47534. [PMID: 31766839 DOI: 10.1021/acsami.9b15570] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Single-atom catalysts (SACs) have recently been shown to have high performance in catalyzing the synthesis of NH3 from N2. Here, we systematically investigated a series of single transition metal atoms anchored on stepped CeO2 (CeO2-S) to screen the potential electrocatalysts for a N2 reduction reaction (NRR) via density functional theory computations. We first demonstrated that these SACs are stable via large calculated binding energies. Second, we evaluated the adsorption of *N2 over CeO2-S-supported single atoms. Here, those systems that can activate N2 molecules were selected as candidates. We then showed that CeO2-S-supported single Mo and Ru atoms have high catalytic activity for NRR via low limiting potentials of -0.52 and -0.35 V, respectively. Meanwhile, the competitive hydrogen evolution reaction is highly suppressed over these two SACs because the adsorption of *N2 is prior to *H. Finally, the origin of the NRR activity over these SACs was investigated. This work offers useful insights into designing high-performance CeO2-based electrocatalysts for NRR.
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Affiliation(s)
- Jiamin Qi
- State Key Laboratory of Photocatalysis on Energy and Environment, College of Chemistry , Fuzhou University , Fuzhou 350002 , China
| | - Liye Gao
- State Key Laboratory of Photocatalysis on Energy and Environment, College of Chemistry , Fuzhou University , Fuzhou 350002 , China
| | - Fenfei Wei
- State Key Laboratory of Photocatalysis on Energy and Environment, College of Chemistry , Fuzhou University , Fuzhou 350002 , China
| | - Qiang Wan
- State Key Laboratory of Photocatalysis on Energy and Environment, College of Chemistry , Fuzhou University , Fuzhou 350002 , China
- Department of Chemistry , University of California, Riverside , Riverside , California 92521 , United States
| | - Sen Lin
- State Key Laboratory of Photocatalysis on Energy and Environment, College of Chemistry , Fuzhou University , Fuzhou 350002 , China
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4
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Khaniya A, Kaden WE. Epitaxial Growth of Ultrathin δ-Like ΜοΝ Films on Ru(0001). Top Catal 2019. [DOI: 10.1007/s11244-019-01198-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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5
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Ghuman KK, Tozaki K, Sadakiyo M, Kitano S, Oyabe T, Yamauchi M. Tailoring widely used ammonia synthesis catalysts for H and N poisoning resistance. Phys Chem Chem Phys 2019; 21:5117-5122. [PMID: 30766991 DOI: 10.1039/c8cp05800h] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Despite many advancements, an inexpensive ammonia synthesis catalyst free from hydrogen and nitrogen poisoning, and capable of synthesizing ammonia under mild conditions is still unknown and is long sought-after. Here we present an active nanoalloy catalyst, RuFe, formed by alloying highly active Ru and inexpensive Fe, capable of activating both N2 and H2 without blocking the surface active sites and thereby overcoming the major hurdle faced by the current best performing pure metal catalysts. This novel RuFe nanoalloy catalyst operates under milder conditions than the conventional Fe catalyst and is less expensive than the so far best performing Ru-based catalysts providing additional advantages. Most importantly, by integrating theory and experiments, we identified the underlying mechanisms responsible for lower surface poisoning of this catalyst, which will provide directions for fabricating poison-free efficient NH3 synthesis catalysts in future.
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Affiliation(s)
- Kulbir Kaur Ghuman
- International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, Motooka 744, Nishi-ku, Fukuoka 819-0395, Japan.
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6
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Kim SY, Lee HW, Pai SJ, Han SS. Activity, Selectivity, and Durability of Ruthenium Nanoparticle Catalysts for Ammonia Synthesis by Reactive Molecular Dynamics Simulation: The Size Effect. ACS APPLIED MATERIALS & INTERFACES 2018; 10:26188-26194. [PMID: 30016859 DOI: 10.1021/acsami.8b05070] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We report a molecular dynamics (MD) simulation employing the reactive force field (ReaxFF), developed from various first-principles calculations in this study, on ammonia (NH3) synthesis from nitrogen (N2) and hydrogen (H2) gases over Ru nanoparticle (NP) catalysts. Using ReaxFF-MD simulations, we predict not only the activities and selectivities but also the durabilities of the nanocatalysts and discuss the size effect and process conditions (temperature and pressure). Among the NPs (diameter = 3, 4, 5, and 10 nm) considered in this study, the 4 nm NPs show the highest activity, in contrast to our intuition that the smallest NP should provide the highest activity, as it has the highest surface area. In addition, the best selectivity is observed with the 10 nm NPs. The activity and selectivity are mainly determined by the hcp, fcc, and top sites on the Ru NP surface, which depend on the NP size. Moreover, the selectivity can be improved more significantly by increasing the H2 pressure than by increasing the N2 pressure. The durability of the NPs can be determined by the mean stress and the stress concentration, and these two factors have a trade-off relationship with the NP size. In other words, as the NP size increases, its mean stress decreases, whereas the stress concentration simultaneously increases. Because of these two effects, the best durability is found with the 5 nm NPs, which is also in contrast to our intuition that larger NPs should show better durability. We expect that ReaxFF-MD simulations, along with first-principles calculations, could be a useful tool in developing novel catalysts and understanding catalytic reactions.
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Affiliation(s)
- Sung-Yup Kim
- Computational Science Research Center , Korea Institute of Science and Technology (KIST) , 5 Hwarangno 14-gil , Seongbuk-gu, Seoul 02792 , Republic of Korea
| | - Hong Woo Lee
- Computational Science Research Center , Korea Institute of Science and Technology (KIST) , 5 Hwarangno 14-gil , Seongbuk-gu, Seoul 02792 , Republic of Korea
| | - Sung Jin Pai
- Computational Science Research Center , Korea Institute of Science and Technology (KIST) , 5 Hwarangno 14-gil , Seongbuk-gu, Seoul 02792 , Republic of Korea
| | - Sang Soo Han
- Computational Science Research Center , Korea Institute of Science and Technology (KIST) , 5 Hwarangno 14-gil , Seongbuk-gu, Seoul 02792 , Republic of Korea
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7
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Shakouri K, Behler J, Meyer J, Kroes GJ. Accurate Neural Network Description of Surface Phonons in Reactive Gas-Surface Dynamics: N 2 + Ru(0001). J Phys Chem Lett 2017; 8:2131-2136. [PMID: 28441867 PMCID: PMC5439174 DOI: 10.1021/acs.jpclett.7b00784] [Citation(s) in RCA: 85] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Accepted: 04/25/2017] [Indexed: 05/20/2023]
Abstract
Ab initio molecular dynamics (AIMD) simulations enable the accurate description of reactive molecule-surface scattering especially if energy transfer involving surface phonons is important. However, presently, the computational expense of AIMD rules out its application to systems where reaction probabilities are smaller than about 1%. Here we show that this problem can be overcome by a high-dimensional neural network fit of the molecule-surface interaction potential, which also incorporates the dependence on phonons by taking into account all degrees of freedom of the surface explicitly. As shown for N2 + Ru(0001), which is a prototypical case for highly activated dissociative chemisorption, the method allows an accurate description of the coupling of molecular and surface atom motion and accurately accounts for vibrational properties of the employed slab model of Ru(0001). The neural network potential allows reaction probabilities as low as 10-5 to be computed, showing good agreement with experimental results.
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Affiliation(s)
- Khosrow Shakouri
- Gorlaeus Laboratories, Leiden
Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
- E-mail: . Phone: +31 (0)71 527
4533. Fax: +31 (0)71 527
4397 (K.S.)
| | - Jörg Behler
- Universität
Göttingen, Institut für Physikalische
Chemie, Theoretische Chemie, Tammannstrasse 6, 37077 Göttingen, Germany
| | - Jörg Meyer
- Gorlaeus Laboratories, Leiden
Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
| | - Geert-Jan Kroes
- Gorlaeus Laboratories, Leiden
Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
- E-mail: . Phone: +31 (0)71 527
4396. Fax: +31 (0)71 527
4397 (G.-J.K.)
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8
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Reactivity and Catalysis at Sites Trans to the [Ru–Ru] Bond. TOP ORGANOMETAL CHEM 2015. [DOI: 10.1007/3418_2015_162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
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9
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Liu X, Zhang X, Bo M, Li L, Tian H, Nie Y, Sun Y, Xu S, Wang Y, Zheng W, Sun CQ. Coordination-resolved electron spectrometrics. Chem Rev 2015; 115:6746-810. [PMID: 26110615 DOI: 10.1021/cr500651m] [Citation(s) in RCA: 111] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Xinjuan Liu
- †Institute of Coordination Bond Metrology and Engineering, College of Materials Science and Engineering, China Jiliang University, Hangzhou 310018, China
| | - Xi Zhang
- ‡Institute of Nanosurface Science and Engineering, Shenzhen University, Shenzhen 518060, China
| | - Maolin Bo
- §Key Laboratory of Low-Dimensional Materials and Application Technologies (Ministry of Education) and School of Materials Science and Engineering, Xiangtan University, Hunan 411105, China
| | - Lei Li
- ∥School of Materials Science, Jilin University, Changchun 130012, China
| | - Hongwei Tian
- ∥School of Materials Science, Jilin University, Changchun 130012, China
| | - Yanguang Nie
- ⊥School of Science, Jiangnan University, Wuxi 214122, China
| | - Yi Sun
- #Harris School of Public Policy, University of Chicago, Chicago, Illinois 60637, United States
| | - Shiqing Xu
- †Institute of Coordination Bond Metrology and Engineering, College of Materials Science and Engineering, China Jiliang University, Hangzhou 310018, China
| | - Yan Wang
- ∇School of Information Technology, Hunan University of Science and Technology, Xiangtan 411201, China
| | - Weitao Zheng
- ∥School of Materials Science, Jilin University, Changchun 130012, China
| | - Chang Q Sun
- ○NOVITAS, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore
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10
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Zaharia T, Kleyn AW, Gleeson MA. Eley-rideal reactions with N atoms at Ru(0001): formation of NO and N(2). PHYSICAL REVIEW LETTERS 2014; 113:053201. [PMID: 25126916 DOI: 10.1103/physrevlett.113.053201] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Indexed: 06/03/2023]
Abstract
Forward-directed NO molecules with large translational energies are formed upon exposure of an O-covered Ru(0001) surface to a nitrogen (N+N_{2}) beam. This is an unequivocal experimental demonstration of the Eley-Rideal reaction for a "heavy" (i.e., nonhydrogenated) neutral system. The time dependence of prompt NO formation exhibits an exceptionally fast decay as a consequence of shifting reaction pathways and probabilities over the course of the exposure. Prompt production shuts down as the O coverage decreases due to competition from more favorable Eley-Rideal production of N_{2}.
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Affiliation(s)
- Teodor Zaharia
- Materials innovation institute (M2i), P.O. Box 5008, 2600 GA Delft, The Netherlands and FOM Institute DIFFER (Dutch Institute For Fundamental Energy Research), P.O. Box 1207, 3430 BE Nieuwegein, The Netherlands
| | - Aart W Kleyn
- FOM Institute DIFFER (Dutch Institute For Fundamental Energy Research), P.O. Box 1207, 3430 BE Nieuwegein, The Netherlands and Van 't Hoff Institute for Molecular Sciences, Faculty of Science, University of Amsterdam, P.O. Box 94157, 1090 GD Amsterdam, The Netherlands
| | - Michael A Gleeson
- FOM Institute DIFFER (Dutch Institute For Fundamental Energy Research), P.O. Box 1207, 3430 BE Nieuwegein, The Netherlands
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11
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Liang Z, Yang HJ, Kim Y, Trenary M. Surface morphology of atomic nitrogen on Pt(111). J Chem Phys 2014; 140:114707. [PMID: 24655198 DOI: 10.1063/1.4868141] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The surface morphology of chemisorbed N on the Pt(111) surface has been studied at the atomic level with low temperature scanning tunneling microscopy (STM). When N is coadsorbed with O on the surface, they form a mixed (2 × 2)-N+O structure. When the surface is covered with N atoms only, isolated atoms and incomplete (2 × 2) patches are observed at low coverages. In a dense N layer, two phases, (√3 × √3)R30°-N and p(2 × 2)-N, are found to coexist at temperatures between 360 and 400 K. The (√3 × √3)R30° phase converts to the (2 × 2) phase as temperature increases. For both phases, nitrogen occupies fcc-hollow sites. At temperatures above 420 K, nitrogen starts to desorb. The p(2 × 2)-N phase shows a honeycomb structure in STM images with three nitrogen and three platinum atoms forming a six-membered ring, which can be attributed to the strong nitrogen binding to the underlying Pt surface.
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Affiliation(s)
- Zhu Liang
- Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607, USA
| | - Hyun Jin Yang
- Surface and Interface Science Laboratory, RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
| | - Yousoo Kim
- Surface and Interface Science Laboratory, RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
| | - Michael Trenary
- Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607, USA
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12
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Hayashi F, Toda Y, Kanie Y, Kitano M, Inoue Y, Yokoyama T, Hara M, Hosono H. Ammonia decomposition by ruthenium nanoparticles loaded on inorganic electride C12A7:e−. Chem Sci 2013. [DOI: 10.1039/c3sc50794g] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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13
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Berry JF. The role of three-center/four-electron bonds in superelectrophilic dirhodium carbene and nitrene catalytic intermediates. Dalton Trans 2012; 41:700-13. [DOI: 10.1039/c1dt11434d] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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14
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Active Sites at Finite Coverages – an STM Investigation of the Dissociation of NO on Ru(0001). ACTA ACUST UNITED AC 2009. [DOI: 10.1524/zpch.219.7.997.67084] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Abstract
We have investigated the role of active sites on a partially adsorbate covered surface. The decomposition of NO molecules on a Ru surface served as model reaction. Experiments were performed in an ultra-high vacuum chamber, by dosing NO on a Ru(0001) single crystal surface at 300 K. The distributions of N and O atoms resulting from the NO decomposition were investigated by scanning tunneling microscopy. We find massive changes compared to the zero-coverage limit that has been studied before. Whereas atomic steps are active sites for the decomposition of the NO molecules at low coverages, the flat terraces also become active at higher coverages. Mobile O atoms on the terraces, formed by the initial dissociation of the NO molecules, are responsible for this effect. Furthermore, narrow terraces fill with N and O atoms at a higher rate than wide terraces, also contrasting the low coverage result. The effect can be understood by the blocked surface diffusion of NO precursors to the steps by N atoms accumulating at the steps. On the approximately half covered surface striking mesoscopic concentration patterns are observed, connected with a demixing of the N and O atoms. Here two effects contribute, the different surface diffusion rates of N and O atoms away from the steps, and the different interactions between the two types of atoms. At saturation NO forms a molecular state, with one NO molecule per unit cell of the (2×2) mixed structure of N and O atoms.
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Pap J, DeBeer George S, Berry J. Delokalisierte Metall-Metall- und Metall-Ligand-Mehrfachbindungen in einer linearen RuRuN-Einheit: Verlängerung einer normalerweise kurzen RuN-Bindung. Angew Chem Int Ed Engl 2008. [DOI: 10.1002/ange.200804397] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Pap J, DeBeer George S, Berry J. Delocalized Metal-Metal and Metal-Ligand Multiple Bonding in a Linear RuRuN Unit: Elongation of a Traditionally Short RuN Bond. Angew Chem Int Ed Engl 2008; 47:10102-5. [DOI: 10.1002/anie.200804397] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Crawford P, Hu P. Importance of Electronegativity Differences and Surface Structure in Molecular Dissociation Reactions at Transition Metal Surfaces. J Phys Chem B 2006; 110:24929-35. [PMID: 17149914 DOI: 10.1021/jp063472u] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The dissociative adsorption of N2 has been studied at both monatomic steps and flat regions on the surfaces of the 4d transition metals from Zr to Pd. Using density functional theory (DFT) calculations, we have determined and analyzed the trends in both straight reactivity and structure sensitivity across the periodic table. With regards to reactivity, we find that the trend in activation energy (Ea) is determined mainly by a charge transfer from the surface metal atoms to the N atoms during transition state formation, namely, the degree of ionicity of the N-surface bond at the transition state. Indeed, we find that the strength of the metal-N bond at the transition state (and therefore the trend in Ea) can be predicted by the difference in Mulliken electronegativity between the metal and N. Structure sensitivity is analyzed in terms of geometric and electronic effects. We find that the lowering of Ea due to steps is more pronounced on the right-hand side of the periodic table. It is found that for the early transition metals the geometric and electronic effects work in opposition when going from terrace to step active site. In the case of the late 4d metals, however, these effects work in combination, producing a more marked reduction in Ea.
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Affiliation(s)
- Paul Crawford
- School of Chemistry and Chemical Engineering, The Queen's University of Belfast, Belfast, BT9 5AG, U.K
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18
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Tautermann CS, Clary DC. Comparative study of cluster- and supercell-approaches for investigating heterogeneous catalysis by electronic structure methods: Tunneling in the reaction N + H → NH on Ru(0001). Phys Chem Chem Phys 2006; 8:1437-44. [PMID: 16633626 DOI: 10.1039/b513577j] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Different ruthenium clusters of various sizes are constructed with the aim to model the Ru(0001) surface with a sufficient accuracy for predicting catalysis by hybrid density functional methods (B3LYP). As an example reaction the hydrogenation step N(ads) + H(ads) --> NH(ads) from the catalytic production cycle of ammonia is chosen. A cluster of 12 ruthenium atoms is found to reproduce experimental geometries and frequencies of the various reactants on the surface satisfyingly. To get the geometries of adsorbed hydrogen qualitatively correct it is shown that second layer atoms have to be included in the model cluster. Boundary effects are believed to have minor effects on optimized geometries, whereas the effects on reaction barriers are significant. A comparison of model cluster calculations to a periodic supercell approach employing plane waves and density functional methods (RPBE) reveals similar barriers for reaction. The influence of tunneling in this reaction is determined by the small curvature tunneling approach on the electronic surfaces.
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Affiliation(s)
- Christofer S Tautermann
- Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, UKOX1 3QZ.
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19
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Tautermann CS, Clary DC. The importance of tunneling in the first hydrogenation step in ammonia synthesis over a Ru(0001) surface. J Chem Phys 2005; 122:134702. [PMID: 15847484 DOI: 10.1063/1.1862612] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The hydrogenation of nitrogen (N(ads)+H(ads)-->NH(ads)) on metal surfaces is an important step in ammonia catalysis. We investigate the reaction dynamics of this hydrogenation step by time independent scattering theory and variational transition state theory (VTST) including tunneling corrections. The potential energy surface is derived by hybrid density functional theory on a model cluster composed of 12 ruthenium atoms resembling a Ru(0001) surface. The scattering calculations are performed on a reduced dimensionality potential energy hypersurface, where two dimensions are treated explicitly and all others are included implicitly by the zero-point correction. The VTST calculations include quantum effects along the reaction coordinate by applying the small curvature tunneling scheme. Even at room temperature (where ruthenium already shows catalytic activity) we find rate enhancement by tunneling by a factor of approximately 70. Inspection of the reaction probabilities shows that the major contribution to reactivity comes from the vibrational ground state of the reactants into vibrationally excited product states. The reaction rates are higher than determined in previous studies, and are compatible with experimental overall rates for ammonia synthesis.
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Affiliation(s)
- Christofer S Tautermann
- Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3HQ, United Kingdom.
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20
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Volpi A, Clary DC. Theoretical Investigation of the Surface Reaction N(ads) + H(ads) → NH(ads) on Ru(0001) Using Density Functional Calculations, Variational Transition-State Theory, and Semiclassical Tunneling Method. J Phys Chem B 2003. [DOI: 10.1021/jp0361475] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Alessandro Volpi
- Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QH, United Kingdom
| | - David C. Clary
- Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QH, United Kingdom
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21
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Diekhöner L, Mortensen H, Baurichter A, Luntz AC. Laser assisted associative desorption of N2 and CO from Ru(0001). J Chem Phys 2001. [DOI: 10.1063/1.1386810] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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22
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Zhang C, Liu ZP, Hu P. Stepwise addition reactions in ammonia synthesis: A first principles study. J Chem Phys 2001. [DOI: 10.1063/1.1384008] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Diekhoner L, Mortensen H, Baurichter A, Luntz AC, Hammer B. Dynamics of high-barrier surface reactions: laser-assisted associative desorption of N2 from Ru(0001). PHYSICAL REVIEW LETTERS 2000; 84:4906-4909. [PMID: 10990828 DOI: 10.1103/physrevlett.84.4906] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/1999] [Indexed: 05/23/2023]
Abstract
We have determined the dynamics and energetics of associative desorption of N2 from Ru(0001) using both an experimental technique, laser-assisted associative desorption, and density functional calculations. These show that N2 is preferentially desorbed into very high vibrational states and that the barriers between gas phase N2 and adsorbed N atoms increase from 2 to >3 eV with increasing N coverage on the surface. This experimental technique is found to be quite insensitive to low barrier steps and defects which complicate interpretations from other methods of studying high-barrier surface reactions.
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Affiliation(s)
- L Diekhoner
- Fysisk Institut, SDU-Odense Universitet, Campusvej 55, DK-5230 Odense M, Denmark
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Diekhöner L, Baurichter A, Mortensen H, Luntz AC. Observation of metastable atomic nitrogen adsorbed on Ru(0001). J Chem Phys 2000. [DOI: 10.1063/1.480817] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Dietrich H, Jacobi K, Ertl G. Vibrations, coverage, and lateral order of atomic nitrogen and formation of NH3 on Ru(101̄0). J Chem Phys 1997. [DOI: 10.1063/1.474042] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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