| 1. |
- Cao, Xinrui, et al.
(författare)
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Catalytic activity of Pd-doped Cu nanoparticles for hydrogenation as a single-atom-alloy catalyst
- 2014
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 16:18, s. 8367-8375
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 2. |
- Cao, Xinrui, et al.
(författare)
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Dehydrogenation of Propane to Propylene by a Pd/Cu Single-Atom Catalyst : Insight from First-Principles Calculations
- 2015
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 119:2, s. 1016-1023
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 3. |
- Cao, Xinrui, et al.
(författare)
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Feasible Catalytic Strategy for Writing Conductive Nanoribbons on a Single-Layer Graphene Fluoride
- 2014
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 118:39, s. 22643-22648
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 4. |
- Cao, Xinrui
(författare)
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First-Principles Modeling of Selected Heterogeneous Reactions Catalyzed by Noble-Metal Nanoparticles
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 5. |
- Cao, Xinrui, et al.
(författare)
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Spin Polarization-Induced Facile Dioxygen Activation in Boron-Doped Graphitic Carbon Nitride
- 2020
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 12:47, s. 52741-52748
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Tidskriftsartikel (refereegranskat)abstract
- Dioxygen (O-2) activation is a vital step in many oxidation reactions, and a graphitic carbon nitride (g-C3N4) sheet is known as a famous semiconductor catalytic material. Here, we report that the atomic boron (B)-doped g-C3N4 (B/g-C3N4) can be used as a highly efficient catalyst for O-2 activation. Our first-principles results show that O-2 can be easily chemisorbed at the B site and thus can be highly activated, featured by an elongated O-O bond (similar to 1.52 angstrom). Interestingly, the O-O cleavage is almost barrier free at room temperatures, independent of the doping concentration. It is revealed that the B atom can induce considerable spin polarization on B/g-C3N4, which accounts for O-2 activation. The doping concentration determines the coupling configuration of net-spin and thus the magnitude of the magnetism. However, the distribution of net-spin at the active site is independent of the doping concentration, giving rise to the doping concentration-independent catalytic capacity. The unique monolayer geometry and the existing multiple active sites may facilitate the adsorption and activation of O-2 from two sides, and the newly generated surface oxygen-containing groups can catalyze the oxidation coupling of methane to ethane. The present findings pave a new way to design g-C3N4-based metal-free catalysts for oxidation reactions.
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| 6. |
- Cao, Xinrui, et al.
(författare)
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Study of the Electronic and Optical Properties of Hybrid Triangular (BN)(x)C-y Foams
- 2014
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 118:38, s. 22181-22187
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Tidskriftsartikel (refereegranskat)abstract
- The triangular foam is a newly designed 3D network structure only containing sp(2) bonding. The triangular carbon foam and its boron nitride analogue are predicted to be metallic and semiconducting, respectively (Chem. Commun. 2011, 47 (15), 4406-4408). Here a series of hybrid 3D network models from the BN- and C-doping of both carbon and BN foams have been designed. These newly designed hybrid (BN)(x)C-y foams are predicted to have comparable stability with their undoped crystalline networks, and the conversion between metallic and semiconducting behavior can be achieved by different doping patterns. Furthermore, these hybrid network structures have strong absorption in a wide range of UV region and relatively weak absorption in the visible-light range, and they should be quite promising for the design of electronic and optical devices.
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| 7. |
- Fu, Qiang, et al.
(författare)
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Identification of the Scaling Relations for Binary Noble-Metal Nanoparticles
- 2013
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 117:6, s. 2849-2854
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 8. |
- Hu, Wei, et al.
(författare)
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Tunable Single-Photon Emission by Defective Boron-Nitride Nanotubes for High-Precision Force Detection
- 2019
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Ingår i: The Journal of Physical Chemistry C. - : AMER CHEMICAL SOC. - 1932-7447 .- 1932-7455. ; 123:14, s. 9624-9628
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Tidskriftsartikel (refereegranskat)abstract
- Boron-nitride nanotubes (BNNTs) hold great potential for electronic, optical, and mechanical applications. By introducing a NBVN defect of removing one nitrogen atom while replacing one boron by nitrogen atom, we examined the use of defective NBVN@BNNTs as a novel type of single-photon emission (SPE) material. Using first-principles calculations to reveal the electronic structures of NBVN@BNNTs, we found that SPE with 1.45-2.29 eV energy can be generated in NBVN@BNNTs with size ranging from (5,0) to (10,0). It is also intriguing to find that their SPE responses are sensitive to the external forces, as indicated by the computed potential energy surfaces and dielectric tensors. Specifically, the (7,0) NBVN@BNNT can serve as an ideal force detector due to its sensitivity and linear response to external force. However, the (5,0) and (6,0) NBVN@BNNTs exhibit insensitive SPE with respect to force applied, and the detection ability of the (8,0), (9,0), and (10,0) NBVN@BNNTs are limited due to the emergence of new photon emissions when tensions become larger than 10 nN. These findings would open a new door for utilizing defective BNNTs for SPE and mechanical detection applications.
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| 9. |
- Shen, Jiacai, et al.
(författare)
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First-Principles Observation of Bonded 2D B4C3 Bilayers
- 2021
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Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 6:20, s. 13218-13224
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional (2D) B-C compounds possess rich allotropic structures with many applications. Obtaining new 2D B4C3 structures is highly desirable due to the novel applications of three-dimensional (3D) B4C3 in protections. In this work, we proposed a new family of 2D B4C3 from the first-principles calculations. Distinct from previous observations, this family of 2D B4C3 consists of bonded 2D B4C3 bilayers. Six different types of bilayers with distinct bonded structures are found. The phonon spectrum calculations and ab initio molecular dynamics simulations at room temperature demonstrate their dynamic and thermal stabilities. Low formation energies suggest the high possibility of realizing such structures in experiments. Rich electronic structures are found, and the predicted Young's moduli are even higher than those of the previous ones. It is revealed that the unique electronic and mechanical properties are rooted in the bonding structures, indicating the prompting applications of this family of 2D B4C3 materials in photovoltaics, nanoelectronics, and nanomechanics.
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| 10. |
- Tang, Shaobin, et al.
(författare)
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Realizing semiconductor-half-metal transition in zigzag graphene nanoribbons supported on hybrid fluorographene-graphane nanoribbons
- 2014
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 16:42, s. 23214-23223
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogenation and fluorination provide promising applications for tuning the properties of graphene-based nanomaterials. Using first-principles calculations, we investigate the electronic and magnetic properties of zigzag graphene nanoribbons (ZGNRs) supported on hydrogenated and fluorinated ZGNRs. Our results indicate that the support of zigzag graphane nanoribbon with its full width has less impact on the electronic and magnetic properties of ZGNRs, whereas the ZGNRs supported on fluorographene nanoribbons can be tuned to metal with almost degenerated ferro-and anti-ferromagnetic states due to the intrinsic polarization of substrate. The ZGNRs supported on zigzag hybrid fluorographene-graphane nanoribbons are spin-polarized half-semiconductors with distinct band gaps for spin-up and spin-down channels. Interestingly, in the absence of an external electric field, the spin-polarized band gaps of supported ZGNRs can be well modulated in the opposite direction by changing the ratio of fluorination to hydrogenation concentration in hybrid substrates. Furthermore, the ZGNRs supported on hybrid nanoribbons exhibit the half-semiconducting to half-metallic behavior transition as the interlayer spacing is gradually reduced, which is realized more easily for the hybrid support with a relatively wide fluorographene moiety compared to its narrow counterpart. Present results provide a novel way for designing substrate-supported graphene spintronic devices.
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