分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-05-02
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 ]
摘要： 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.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-05-02
Zhou, Y [Zhou, Yu][ 1,2 ]
Chen, GF [Chen, Guofei][ 1 ]
Wang, W [Wang, Wei][ 1 ]
Wei, LH [Wei, Lihong][ 1 ]
Zhang, QJ [Zhang, Qiuju][ 1 ]
Song, LP [Song, Liping][ 2 ]
Fang, XZ [Fang, Xingzhong][ 1 ]
摘要： Two series of poly(ester imide)s derived from bis(trimellitic acid anhydride) phenyl ester (TAHQ) and bis[(3,4- dicarboxylic anhydride) phenyl] terephthalate (PAHP), as well as poly(ether imide)s based on hydroquinone diphthalic anhydride (HQDPA), were synthesized with aromatic diamines via solution polycondensation. These polyimide films were transparent with an ultraviolet-visible absorption cut-off wavelength below 375 nm, and with tensile strengths of 42.0–83.8 MPa, tensile moduli of 2.5–4.7 GPa and elongations at break of 2.1–5.4%. Compared with the poly(ether imide)s, the poly(ester imide)s showed higher glass transition temperatures (Tg), lower water absorption (WA) and lower temperature of 5% weight loss (Td5%). Moreover, the poly(ester imide)s derived from PAHP with a low electron affinity of 2.04 eV by theoretical calculation achieved better transparency, lower WA and slightly lower Tg than the corresponding TAHQ- based poly(ester imide)s.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-05-02
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 ]
摘要： 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.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-05-02
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 ]
摘要： 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.
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