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First-Principles Modeling of Selected Heterogeneous Reactions Catalyzed by Noble-Metal Nanoparticles
KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Heterogeneous catalysis is an important branch in catalysis, in which the catalyst and reactants are in different physical phases. In this thesis, we have carried out extensive first-principles calculations to explore the selected heterogeneous reactions catalyzed by the noble-metal nanoparticles. The major results of the thesis fall into two categories: (1) the discovery of the scaling relations for predicting the catalytic activity of nanoparticles; (2) the computational characterization of the catalytic activity and mechanism for specific catalytic reactions. For the first category, we have made efforts to develop the scaling relations for binary noble-metal nanoparticles. The obtained results show that the scaling relation not only holds at the nanoscale, but can also be unified with those obtained for the extended surfaces. Our findings shed new light for the efficient screening of nanoparticles with superior catalytic properties. The second part of the thesis summarizes our studies on different catalytic systems. One of the focuses is to study the catalytic properties of the single Pd-doped Cu55 nanoparticle toward H2 dissociation and propane dehydrogenation. The possible reaction mechanisms and effects of the single and multiple Pd doping on the catalytic activity have been extensively examined. Our calculations reveal that single-Pd-doped Cu55 cluster bears good balance between the maximum use of the noble metal and the high activity, and it may serve as a promising single-atom catalyst. We have also systematically studied the reduction process of graphene fluoride catalyzed by the Pt-coated metallic tip under different atmospheres, aiming to provide a feasible strategy for scanning probe lithography to fabricate electronic circuits at the nanoscale on graphene fluoride. It is found that the tip-induced reduction of graphene fluoride with assistance of pure hydrogen atmosphere is facile despite the release of hazard hydride fluoride. The ethylene molecule is predicted to be an excellent acceptor for fluoride abstraction from graphene fluoride, but the corresponding defluorination cycle can not be recycled. Our calculations have finally revealed that under the mixture hydrogen and ethylene atmosphere, the Pt-coated tip can effectively and sequentially reduce graphene fluoride with the release of relatively harmless reduction product, fluoroethane. The proposed cyclic reduction strategy is energetically highly favorable and is ready to be employed in experiments. Our theoretical studies provide yet another convincing example to demonstrate the power of the density functional theory for studying the nano-catalysis. It should also been mentioned that the present calculations are restricted to relatively small-sized clusters due to the limited computational resources. It is highly desirable to further study complicated interfacial systems and to provide a full picture of heterogeneous catalysis with the aid of ab initio molecular dynamics simulations in the future.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. , x, 59 p.
Series
TRITA-BIO-Report, ISSN 1654-2312 ; 2015:6
National Category
Natural Sciences Natural Sciences
Identifiers
URN: urn:nbn:se:kth:diva-159883ISBN: 978-91-7595-454-7 (print)OAI: oai:DiVA.org:kth-159883DiVA: diva2:787528
Public defence
2015-03-06, FA32, Roslagstullsbacken 21, AlbaNova, KTH, Stockholm, 14:30 (English)
Opponent
Supervisors
Note

QC 20150211

Available from: 2015-02-11 Created: 2015-02-10 Last updated: 2015-02-11Bibliographically approved
List of papers
1. Identification of the Scaling Relations for Binary Noble-Metal Nanoparticles
Open this publication in new window or tab >>Identification of the Scaling Relations for Binary Noble-Metal Nanoparticles
2013 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, no 6, 2849-2854 p.Article in journal (Refereed) Published
Abstract [en]

There exist a great many varieties of nanoparticles whose catalytic activities can be widely adjusted by changing their composition, shape, and size. Norskov's concepts to correlate the d-band center, adsorption energy, and activation energy offer an innovative approach to efficiently investigate the catalytic properties. Taking binary noble-metal polyhedral nanoparticles as representative systems, we found from first-principles simulations that the well-established scaling relations of the adsorption energies for extended surfaces can be seamlessly extended to the nanoscale. A systematic investigation of the correlation relations of the adsorption energies between the AH(x) groups and the corresponding A atoms in the binary noble-metal polyhedral nanoclusters of different compositions, shapes, and sizes clearly demonstrates the linear scaling relation. More remarkably, the scaling relation at the nanoscale can be effectively unified with the well-established scaling relations for extended surfaces. Such a description should be extremely helpful for the efficient screening of nanoparticles with superior catalytic properties.

Keyword
Oxygen Reduction Activity, Catalytic Co Oxidation, Colloidal Solution, Surface-Chemistry, Alloy Catalysts, Formic-Acid, Shape, Nanocrystals, Size, Clusters
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-119738 (URN)10.1021/jp311104w (DOI)000315181800055 ()2-s2.0-84873972290 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20130322

Available from: 2013-03-22 Created: 2013-03-21 Last updated: 2017-12-06Bibliographically approved
2. Catalytic activity of Pd-doped Cu nanoparticles for hydrogenation as a single-atom-alloy catalyst
Open this publication in new window or tab >>Catalytic activity of Pd-doped Cu nanoparticles for hydrogenation as a single-atom-alloy catalyst
2014 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, no 18, 8367-8375 p.Article in journal (Refereed) Published
Abstract [en]

The single atom alloy of extended surfaces is known to provide remarkably enhanced catalytic performance toward heterogeneous hydrogenation. Here we demonstrate from first principles calculations that this approach can be extended to nanostructures, such as bimetallic nanoparticles. The catalytic properties of the single-Pd-doped Cu-55 nanoparticles have been systemically examined for H-2 dissociation as well as H atom adsorption and diffusion, following the concept of single atom alloy. It is found that doping a single Pd atom at the edge site of the Cu-55 shell can considerably reduce the activation energy of H-2 dissociation, while the single Pd atom doped at the top site or in the inner layers is much less effective. The H atom adsorption on Cu-55 is slightly stronger than that on the Cu(111) surface; however, a larger nanoparticle that contains 147 atoms could effectively recover the weak binding of the H atoms. We have also investigated the H atom diffusion on the 55-atom nanoparticle and found that spillover of the produced H atoms could be a feasible process due to the low diffusion barriers. Our results have demonstrated that facile H-2 dissociation and weak H atom adsorption could be combined at the nanoscale. Moreover, the effects of doping one more Pd atom on the H-2 dissociation and H atom adsorption have also been investigated. We have found that both the doping Pd atoms in the most stable configuration could independently exhibit their catalytic activity, behaving as two single-atom-alloy catalysts.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2014
Keyword
Density-Functional-Theory, Oxygen Reduction Activity, Total-Energy Calculations, Core-Shell Nanoparticles, Finding Saddle-Points, Near-Surface Alloys, Wave Basis-Set, H-2 Dissociation, Cu(111) Surface, Metal-Clusters
National Category
Other Chemistry Topics Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-145619 (URN)10.1039/c4cp00399c (DOI)000334602900020 ()2-s2.0-84898449548 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20140523

Available from: 2014-05-23 Created: 2014-05-23 Last updated: 2017-12-05Bibliographically approved
3. Dehydrogenation of Propane to Propylene by a Pd/Cu Single-Atom Catalyst: Insight from First-Principles Calculations
Open this publication in new window or tab >>Dehydrogenation of Propane to Propylene by a Pd/Cu Single-Atom Catalyst: Insight from First-Principles Calculations
2015 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 2, 1016-1023 p.Article in journal (Refereed) Published
Abstract [en]

The catalytic properties of the single-Pd-doped Cu55 nanoparticle toward propane dehydrogenation have been systemically investigated by first-principles calculations, and the possible reaction mechanisms and effects of the single and multiple Pd doping on the catalytic activity have been discussed. Calculations reveal that the low-energy catalytic conversion of propane to propylene by the Pd/Cu single-atom catalyst comprises the initial crucial C–H bond breaking at either the methyl or methylene group, the facile diffusion of detached H atoms on the Cu surface, and the subsequent C–H bond dissociation activation of the adsorbed propyl species. The single-Pd-doped Cu55 nanoparticle shows remarkable activity toward C–H bond activation, and the presence of relatively inactive Cu surface is beneficial for the coupling and desorption of detached H atoms and can reduce side reactions such as deep dehydrogenation and C–C bond breaking. The single-Pd-doped Cu55 cluster bears good balance between the maximum use of the noble metal and the activity, and it may serve as a promising single-atom catalyst toward selective dehydrogenation of propane.

Keyword
Atoms, Calculations, Catalyst activity, Catalysts, Chemical activation, Dehydrogenation, Nanoparticles, Precious metals, Propane, Propylene, C-H bond dissociation, Catalytic conversion, Catalytic properties, CH-bond activation, Dehydrogenation of propanes, First-principles calculation, Propane dehydrogenation, Reaction mechanism
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-159882 (URN)10.1021/jp508625b (DOI)000348094000017 ()2-s2.0-84949115465 (Scopus ID)
Note

QC 20150211

Available from: 2015-02-10 Created: 2015-02-10 Last updated: 2017-12-04Bibliographically approved
4. Feasible Catalytic Strategy for Writing Conductive Nanoribbons on a Single-Layer Graphene Fluoride
Open this publication in new window or tab >>Feasible Catalytic Strategy for Writing Conductive Nanoribbons on a Single-Layer Graphene Fluoride
Show others...
2014 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 39, 22643-22648 p.Article in journal (Refereed) Published
Abstract [en]

An accessible method for local reduction of graphene fluoride catalyzed by the Pt-coated nanotip with the assistance of a mixture of hydrogen and ethylene atmosphere is proposed and fully explored theoretically. Detailed mechanisms and roles of hydrogen and ethylene molecules in the cyclic reduction is discussed based on extensive first-principles calculations. It is demonstrated that the proposed cyclic reduction strategy is energetically favorable. This new strategy can be effectively applied in scanning probe lithography to fabricate electronic circuits at the nanoscale on graphene fluoride under mild conditions.

National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-155462 (URN)10.1021/jp507469r (DOI)000342652000027 ()2-s2.0-84907741300 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20141113

Available from: 2014-11-13 Created: 2014-11-06 Last updated: 2017-12-05Bibliographically approved

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