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1. chinaXiv:201705.00605 [pdf]

First-principles study of NO oxidation on Pt/CaTiO3 interface

Li, HL [Li, Huailong][ 1,2 ]; Duan, XM [Duan, Xiangmei][ 2 ]; Suo, YG [Suo, Yange][ 1 ]; Zhang, QJ [Zhang, Qiuju][ 1 ]; Chen, L [Chen, Liang][ 1 ]
Subjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

A well-dispersed noble metal on perovskite support is expected to show good catalytic ability for NO oxi- dation under oxygen-rich conditions, which is an important step in reducing NO in lean burn exhaust gas. In this study, we investigated the catalytic oxidation of NO to NO2 on a Pt4/CaTiO3 (001) model to eval- uate interfacial effect. Results showed that O2 preferred Pt–Ti interface sites, and that the decomposition of O2 required a dissociation activation barrier of 0.97 eV. The decomposed O–O on the interface required nearly no activation barrier in the subsequent NO oxidation. However, the most rate-limiting step involved the desorption of the second formed NO2 from interfacial Pt4/CaTiO3 (0 0 1), which yielded a sig- nificant desorption barrier of 2.63 eV. These findings can help understand the oxidation process of NO to NO2 on noble-metal–perovskite interface.

submitted time 2017-05-02 Hits13694Downloads718 Comment 0

3. chinaXiv:201705.00536 [pdf]

Kinetically Stabilized Pd@Pt Core-Shell Octahedral Nanoparticles with Thin Pt Layers for Enhanced Catalytic Hydrogenation Performance

Zhang, PP [Zhang, Peipei][ 1,2 ]; Hu, YB [Hu, Yibo][ 1 ]; Li, BH [Li, Baihai][ 3 ]; Zhang, QJ [Zhang, Qiuju][ 1 ]; Zhou, C [Zhou, Chen][ 1 ]; Yu, HB [Yu, Hongbo][ 1 ]; Zhang, XJ [Zhang, Xuejun][ 2 ]; Chen, L [Chen, Liang][ 1 ]; Eichhorn, B [Eichhorn, Bryan][ 4 ]; Zhou, SH [Zhou, Shenghu][ 1 ]
Subjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

This study investigates the structural stability of small Pd@Pt core@shell octahedral nanoparticles (NPs) and their shell thickness dependent catalytic performance for p-chloronitrobenzene hydrogenation with H2. The 6?8 nm Pd@Pt octahedral NPs are prepared by a sequential reduction method, and the characterization results confirm that Pd@Pt octahedral NPs with one to four atomic Pt layers can be controllably synthesized. The Pd@Pt octahedral NPs with one atomic Pt layer demonstrate excellent structural stability with the maintenance of core?shell structures as well as high catalytic stability during cycle to cycle catalytic p-chloronitrobenzene hydrogenation reactions. The alumina-supported Pd@Pt octahedral NPs illustrate a superior catalytic performance relative to individual Pt and Pd and their physical mixtures. Theoretical calculations by density functional theory suggest that the unexpected structural stability for Pd@Pt octahedral NPs with thin Pt shells and their corresponding catalytic stability during hydrogenation reactions can be ascribed to the strong binding between Pt surfaces and reactants/products in catalytic reactions. The enhanced catalytic performance of Pd@Pt octahedral NPs possibly originates from the core?shell interaction, which adjusts the electronic state of surface Pt atoms to be suitable for selective p-chloronitrobenzene hydrogenation.

submitted time 2017-05-02 Hits2399Downloads433 Comment 0

4. chinaXiv:201705.00482 [pdf]

A first-principles study of CO oxidation by surface oxygen on Pt-incorporated perovskite catalyst [CaPtxTi1-xO3]

Zhang, QJ [Zhang, Qiuju][ 1 ]; Li, BH [Li, Baihai][ 1,2 ]; Wang, HY [Wang, Houyuan][ 1 ]; Suo, YG [Suo, Yange][ 1 ]; Chen, L [Chen, Liang][ 1 ]
Subjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

In the present work, we investigated the structural and catalytic properties of a prototype system Pt-doped CaTiO3 by means of first principles calculations. We paid particular attention to the aggregation and penetration of Pt on different surfaces of CaTiO3, and subsequent CO oxidation by surface oxygen atoms on Pt-doped CaTiO3. Our calculations indicate that CO oxidation can potentially take place when Pt is doped on the first layer of CaTiO3(001). The activation barriers are calculated to be 0.20–0.45 eV. The possibly induced O vacancy on the surface will produce a magnetic behavior by breaking the spin density symmetry due to one Pt–O bond cleavage. Our study is expected to provide an insight into the catalytic behavior of Pt ions in Pt-doped perovskite toward the oxidation of exhaust gas.

submitted time 2017-05-02 Hits718Downloads413 Comment 0

5. chinaXiv:201705.00440 [pdf]

Morphology-Dependent Electrochemical Performance of Zinc Hexacyanoferrate Cathode for Zinc-Ion Battery

Zhang, LY [Zhang, Leyuan][ 1 ]; Chen, L [Chen, Liang][ 1 ]; Zhou, XF [Zhou, Xufeng][ 1 ]; Liu, ZP [Liu, Zhaoping][ 1 ]
Subjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

Zinc hexacyanoferrate (ZnHCF) which is a dimorphic (cubic or rhombohedral) Prussian blue analogue and can be intercalated by both monovalent and divalent ions,is a promising cathode material for rechargeable aqueous metal-ion batteries.In this paper, a simple co-precipitation method is developed to tune the particle morphology of ZnHCF by adjusting the dropping speed at room temperature. Three polyhedral ZnHCF particles, with cubooctahedral, truncated octahedral or octahedral shapes, are obtained at room temperature. Structural transformation from cubic phase of as-prepared ZnHCF to rhombohedral phase is observed by further dehydration of the sample at 70 °C, whereas the dehydrated ZnHCF crystals still hold the identical polyhedral shape as that of the cubic phase particles. Then the in uence of shape and facets on electrochemical performance is studied for polyhedral ZnHCF with rhombohedral structure (RZnHCF). RZnHCF sample with cubooctahedral shape possesses the best rate capability and cyclic stability comparing with RZnHCF particles having truncated octahedral or octahedral shapes. Furthermore, the structure of cuboctahedron RZnHCF particles during electrochemical cycling has been monitored with ex situ X-ray di raction to demonstrate the reversible zinc-ion intercalation mechanism.

submitted time 2017-05-02 Hits888Downloads571 Comment 0

6. chinaXiv:201705.00418 [pdf]

Water-mediated cation intercalation of open-framework indium hexacyanoferrate with high voltage and fast kinetics

Chen, L [Chen, Liang][ 1 ]; Shao, HZ [Shao, Hezhu][ 1 ]; Zhou, XF [Zhou, Xufeng][ 1 ]; Liu, GQ [Liu, Guoqiang][ 1 ]; Jiang, J [Jiang, Jun][ 1 ]; Liu, ZP [Liu, Zhaoping][ 1 ]

Rechargeable aqueous metal-ion batteries made from non-flammable and low-cost materials offer promising opportunities in large-scale utility grid applications, yet low voltage and energy output, as well as limited cycle life remain critical drawbacks in t

submitted time 2017-05-02 Hits635Downloads364 Comment 0

7. chinaXiv:201607.00035 [pdf]

An efficient m-step Levenberg-Marquardt method for nonlinear equations

Chen, Liang; Ma, Yanfang; Su, Chencheng
Subjects: Mathematics >> Control and Optimization.

In this paper, we construct and analyze an efficient m-step Levenberg-Marquardt method for nonlinear equations. The main advantage of this method is that the m-step LM method could save more Jacobian calculations with frozen $(J_k^TJ_k+\lambda_kI)^{-1}J_k^T$ at every iteration. Under the local error bound condition which is weaker than nonsingularity, the m-step LM method has been proved to have $(m+1)$th convergence order. The global convergence has also been given by trust region technique. Numerical results show that the m-step LM method is efficient and could save many calculations of the Jacobian especially for large scale problems.

submitted time 2016-07-11 Hits2985Downloads1330 Comment 0

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