Structure sensitivity in acetylene reactions over bimetallic Pd/W surfaces

Acetylene reactions over a Pd/W(111) surface are found to exhibit size effects on the nanometer scale. Upon annealing 1 ML Pd/W(111), pyramidal facets are formed having bcc(211) faces with nanometer dimensions. The facets grow as a function of annealing time and temperature. Temperature-programmed desorption (TPD) spectra of benzene and ethylene, formed reactively following acetylene adsorption, change as a function of relative facet size. Results are compared to spectra from a similar experiment performed on planar Pd/W(211). TPD of chemisorbed benzene from several different Pd/W surface morphologies are also presented. The data show that structure sensitivity is exhibited for reactively-formed ethylene and benzene, as well as for chemisorbed benzene.     

汽车用线缆的新发展

本文介绍随着汽车工业的现代化而对汽车内所用的电线电缆的改进。这些改进主要是用双金属线(铜包钢和铜包铝)来替代传统的铜导线;用新型的可交联聚酯弹性体来替代传统的绝缘材料。其主要目的在于减小线缆的尺寸和重量,增加了线缆的柔软性、耐热水性和耐热性等机械物理性能。文章描述了这些新产品的开发、性能试验和应用。     

Bimetallic CuCo2S4 Nanozymes with Enhanced Peroxidase Activity at Neutral pH for Combating Burn Infections

Peroxidase-mimicking nanozymes that can generate toxic hydroxyl radicals (^.OH) hold great promise as antibacterial alternatives. However, most of them display optimal performance under strongly acidic conditions (pH 3–4), and are thus not feasible for many medical uses, including burn infections with a wound pH close to neutral. Herein, we report a copper-based nanozyme (CuCo₂S₄) that exhibits intrinsic peroxidase-like activity and can convert H₂O₂ into ^.OH at neutral pH. In particular, bimetallic CuCo₂S₄ nanoparticles (NPs) exhibited enhanced peroxidase-like activity and antibacterial capacity, superior to that of the corresponding monometallic CuS and CoS NPs. The CuCo₂S₄ nanozymes possessed excellent ability to kill various bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). Furthermore, this CuCo₂S₄ nanozymes could effectively disrupt MRSA biofilms in vitro and accelerate MRSA-infected burn healing in vivo. This work provides a new peroxidase mimic to combat bacteria in neutral pH milieu and this CuCo₂S₄ nanozyme could be a promising antibacterial agent for the treatment of burn infections.     

Textural properties evolution of Ir and Ru supported on alumina catalysts during hydrazine decomposition in satellite thruster

Ir/Al₂O₃, Ru/Al₂O₃, and Ir-Ru/Al₂O₃ catalysts with total metallic contents of 30% in mass were prepared by an incipient wetness method. The characterization of these materials, before and after their use for hydrazine decomposition in a satellite thruster, was performed by measurement techniques of specific surface area, volume and pores size distribution, H₂ chemisorption, TEM and basic chemical analysis. An average decrease of 11% in the BET surface area was observed, independent of the catalyst composition. The total specific pore volume remained unchanged because the volume reduction in the size range diameters between 1.0 and 10 nm was compensated by the increase in the diameters size range between 10 and 100 nm. A reduction of the H₂ quantity adsorbed on the Ir/Al₂O₃ catalyst can be explained by the metal loss through erosion as well as by its partial occlusion within the pores of the alumina support. On the other hand, catalysts containing Ru showed an increase of H₂ chemisorbed amount, attributed to a more complete reduction of this material after hydrazine decomposition, in spite of the erosion and occlusion losses. Such observations were confirmed by TEM, which showed a great stability of the distributions of the metallic particle sizes in all catalysts.     

Cobalt-Molybdenum Sulfide Catalysts Prepared by In Situ Activation of Bimetallic (Co-Mo) Alkylthiomolybdates

Unsupported cobalt-molybdenum sulfide catalysts were prepared from bimetallic CoMo alkyl precursors by in situ activation during the hydrodesulfurization (HDS) of dibenzothiophene (DBT). The bimetallic CoMo precursors were prepared by reaction of tetraalkylammonium thiomolybdate salts, (R₄N)₂MoS₄ (where R = H, methyl, butyl, pentyl or hexyl), with CoCl₂ in water at a Co/Mo molar ratio of 0.3. These catalysts exhibit a Swiss-cheese-like morphology, high surface areas (from 52 up to 320 m²/g), high content of carbon (C/Mo = 2.2-3.3) and type IV adsorption-desorption isotherms of nitrogen. The in situ activation of these tetraalkylammonium thiobimetalate precursors leads to a mesoporous structure with pore size ranging from 2 to 4.5 nm. X-ray diffraction showed that the structure of unsupported cobalt-molybdenum sulfide catalysts corresponds to a poorly crystalline structure characteristic of 2H-MoS₂ with low-stacked layers. The nature of the alkyl group strongly affects both the surface area and the HDS activity. The catalytic activity is strongly enhanced when using carbon-containing precursors; the CoMo catalysts prepared by in situ activation of Co/[N(C₄H₉)₄]₂MoS₄ presents the highest HDS activity. The highest surface area of the catalysts was observed for the CoMo catalyst formed from Co/[N(C₆H₁₃)₄N]₂MoS₄.     

Palladium/Copper Bimetallic System‐Mediated Cross‐Coupling of Alkynes and Alkenes: Two Strategies to Suppress β‐H Elimination on Alkyl‐Palladium Center

This paper describes two efficient strategies to suppress β‐H elimination during the palladium/copper bimetallic system‐mediated cross‐coupling between alkynamides and alkenes. Remote donor groups with the terminal olefins, such as toluenesulfonamide, phosphate, sulfone, etc., cooperate with the amide of alkynamides and chelate the palladium active center, to promote C(sp³) O bond formation by suppressing the β‐H elimination. Another strategy uses the rigid structure of norbornene to make an intermediate without a syn‐β‐hydrogen to achieve reductive elimination of the C Cl bond.

     

钌钯双金属催化剂固载顺序控制及性能

以Al_2O_3、PdCl_2和RuCl_3为原料,采用水溶液浸渍法,通过控制固载顺序、制备流程以及焙烧温度等条件,制得系列负载型Ru Pd双金属催化剂,并用于对苯二甲酸二甲酯(DMT)制取1,4-环己烷二甲酸二甲酯(DMCD)的选择性加氢过程。其中,Ru和Pd的总负载量为0.3%(以催化剂总质量为基准,下同),且m(Ru)∶m(Pd)=1∶1。结果发现,采用先Ru后Pd(Ru-Pd)式固载顺序和浸渍-干燥-浸渍-干燥-焙烧(IDIDC)型制备流程,并在450℃下焙烧后,所得负载型Ru-Pd双金属催化剂的反应性能最佳,在6 MPa、180℃下,DMT转化率为89.6%,DMCD选择性为96.0%,DMCD产率为85.9%。这可能与Ru-Pd中大粒径粒子的形成受到抑制、粒径尺寸和分布更小、比表面积和总孔容更高、表面Pd原子摩尔分数较高以及Ru/Pd物质的量比较低有关。     

Interaction of H2,n-butane and cis-2-butene with Pt and Pt In in NaY: a microcalorimetric study

Pt NaY and Pt In NaY adsorption properties have been compared by using probes like H₂, C₄H₁₀, 2-C₄H₈ and microcalorimetry. It appears that the addition of In to Pt does not change the initial heat of H₂ chemisorption but decreases the initial heat of butane and butene chemisorption.     

Cu3P and Ni2P co-modified g-C3N4 nanosheet with excellent photocatalytic H2 evolution activities

Copper-nickel phosphides/ graphite-like phase carbon nitride (Cu₃P-Ni₂P/g-C₃N₄) composites were obtained through a facile one-pot in situ solvothermal approach. The coexistence of Cu₃P and Ni₂P plays an important role in enhancing the catalytic activity of g-C₃N₄. The 7 wt% Cu₃P-Ni₂P/g-C₃N₄ bimetallic phosphide photocatalyst demonstrates the best photocatalytic hydrogen (H₂) evolution rate of 6529.8 μmol g⁻¹ h⁻¹, which is 80.7-fold higher than that of g-C₃N₄. The apparent quantum yield (AQE) was determined to be 18.5% at 400 nm over the 7% Cu₃P-Ni₂P/g-C₃N₄. This in situ growth strategy produced intimate contact interfaces, leading to a significantly promoted separation of charge carriers, and hence strengthened the photocatalytic H₂ production. Moreover, the coexistence of Cu₃P and Ni₂P reduced the overpotential of H₂ during the evolution process, further benefiting H₂ production. Finally, the photocatalytic enhancement mechanism was proposed and verified by fluorescence and electrochemical analysis. This work provides a low-cost strategy to synthesize nonprecious bimetallic phosphides/carbon nitride photocatalyst with outstanding H₂ production activity. © 2020 Society of Chemical Industry     

PdnY(n=1-5)团簇的密度泛函研究

在相对论有效原子实势近似下,用密度泛函方法(B3L YP/ANL2DZ)计算了二元合金团簇PdnY(n=1-5)可能的几何构型和对应的电子态,得到一系列稳定异构体的结构参数、电子态、能量和谐振频率.用最高占据轨道(HOMO)与最低空轨道(LUMO)之间的能级间隙描述团簇的稳定性,Pd2Y团簇的能级间隙最大,PdY团簇的能级间隙最小.Pd-Y相互作用改变了纯钯团簇的几何构形和稳定性.计算结果有助于系统研究Pd-Y体系的物理化学性质.