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排序方式: 共有116条查询结果,搜索用时 93 毫秒
111.
Siyu Zhou Dr. Marc Figueras-Valls Dr. Yifeng Shi Dr. Yong Ding Prof. Dr. Manos Mavrikakis Prof. Dr. Younan Xia 《Angewandte Chemie (International ed. in English)》2023,62(42):e202306906
We report for the first time that Pd nanocrystals can absorb H via a “single-phase pathway” when particles with a proper combination of shape and size are used. Specifically, when Pd icosahedral nanocrystals of 7- and 12-nm in size are exposed to H atoms, the H-saturated twin boundaries can divide each particle into 20 smaller single-crystal units in which the formation of phase boundaries is no longer favored. As such, absorption of H atoms is dominated by the single-phase pathway and one can readily obtain PdHx with anyx in the range of 0–0.7. When switched to Pd octahedral nanocrystals, the single-phase pathway is only observed for particles of 7 nm in size. We also establish that the H-absorption kinetics will be accelerated if there is a tensile strain in the nanocrystals due to the increase in lattice spacing. Besides the unique H-absorption behaviors, the PdHx (x=0–0.7) icosahedral nanocrystals show remarkable thermal and catalytic stability toward the formic acid oxidation due tothe decrease in chemical potential for H atoms in a Pd lattice under tensile strain. 相似文献
112.
Scott DJ Manos S Coveney PV Rossiny JC Fearn S Kilner JA Pullar RC Alford NM Axelsson AK Zhang Y Chen L Yang S Evans JR Sebastian MT 《Journal of chemical information and modeling》2008,48(2):449-455
We present work on the creation of a ceramic materials database which contains data gleaned from literature data sets as well as new data obtained from combinatorial experiments on the London University Search Instrument. At the time of this writing, the database contains data related to two main groups of materials, mainly in the perovskite family. Permittivity measurements of electroceramic materials are the first area of interest, while ion diffusion measurements of oxygen ion conductors are the second. The nature of the database design does not restrict the type of measurements which can be stored; as the available data increase, the database may become a generic, publicly available ceramic materials resource. 相似文献
113.
Alexandropoulos DI Manos MJ Papatriantafyllopoulou C Mukherjee S Tasiopoulos AJ Perlepes SP Christou G Stamatatos TC 《Dalton transactions (Cambridge, England : 2003)》2012,41(16):4744-4747
A Mn(III)(4)Ni(II)(4) molecular square exhibiting slow magnetization relaxation has been prepared from the reaction of a Mn(II)(4)Mn(III)(6)Mn(IV)(2) cluster and a simple Ni(II) source. 相似文献
114.
Peter Ferrin Shampa Kandoi Anand Udaykumar Nilekar Manos Mavrikakis 《Surface science》2012,606(7-8):679-689
Periodic, self-consistent DFT-GGA(PW91) calculations are used to study the interaction of hydrogen with different facets of seventeen transition metals—the (100) and (111) facets of face-centered cubic (fcc) metals, the (0001) facet of hexagonal-close packed (hcp) metals, and the (100) and (110) facets of body-centered cubic (bcc) metals. Calculated geometries and binding energies for surface and subsurface hydrogen are reported and are, in general, in good agreement with both previous modeling studies and experimental data. There are significant differences between the binding on the close-packed and more open (100) facets of the same metal. Geometries of subsurface hydrogen on different facets of the same metal are generally similar; however, binding energies of hydrogen in the subsurface of the different facets studied showed significant variation. Formation of surface hydrogen is exothermic with respect to gas-phase H2 on all metals studied with the exception of Ag and Au. For each metal studied, hydrogen in its preferred subsurface state is always less stable than its preferred surface state. The magnitude of the activation energy for hydrogen diffusion from the surface layer into the first subsurface layer is dominated by the difference in the thermodynamic stability of these two states. Diffusion from the first subsurface layer to one layer further into the bulk does not generally have a large thermodynamic barrier but still has a moderate kinetic barrier. Despite the proximity to the metal surface, the activation energy for hydrogen diffusion from the first to the second subsurface layer is generally similar to experimentally-determined activation energies for bulk diffusion found in the literature. There are also some significant differences in the activation energy for hydrogen diffusion into the bulk through different facets of the same metal. 相似文献
115.
The adsorption properties of a variety of atomic species (H, O, N, S, and C), molecular species (N2, HCN, CO, NO, and NH3) and molecular fragments (CN, NH2, NH, CH3, CH2, CH, HNO, NOH, and OH) are calculated on the (111) facet of palladium using periodic self-consistent density functional theory (DFT–GGA) calculations at ¼ ML coverage. For each species, we determine the optimal binding geometry and corresponding binding energy. The vibrational frequencies of these adsorbed species are calculated and are found to be in good agreement with experimental values that have been reported in literature. From the binding energies, we calculate potential energy surfaces for the decomposition of NO, CO, N2, NH3, and CH4 on Pd(111), showing that only the decomposition of NO is thermochemically preferred to its molecular desorption. 相似文献
116.