Efficient Catalytic Production of Hydrogen Peroxide Using Tin-containing Zeolite Fixed Palladium Nanoparticles with Oxidation Resistance

The metal surfaces tend to be oxidized in air through dissociation of the O−O bond of oxygen to reduce the performances in various fields. Although several ligand modification routes have alleviated the oxidation of bulky metal surfaces, it is still a challenge for the oxidation resistance of small-size metal nanoparticles. Herein, we fixed the small-size Pd nanoparticles in tin-contained MFI zeolite crystals, where the tin acts as an electron donor to efficiently hinder the oxidation of Pd by weakening the adsorption of molecular oxygen and suppressing the O−O cleavage. This oxidation-resistant Pd catalyst exhibited superior performance in directly synthesizing hydrogen peroxide from hydrogen and oxygen, with the productivity of hydrogen peroxide at ≈10,170 mmol g_Pd⁻¹ h⁻¹, steadily outperforming the catalysts tested previously. This work leads to the hypothesis that tin is an electron donor to realize oxidation-resistant Pd within zeolite crystals for efficient catalysis to overcome the limitation of generally supported Pd catalysts and further motivates the use of oxidation-resistant metal nanoparticles in various fields.     

Supramolecular Polymer Ion Conductor with Weakened Li Ion Solvation Enables Room Temperature All-Solid-State Lithium Metal Batteries

Improved durability, enhanced interfacial stability, and room temperature applicability are desirable properties for all-solid-state lithium metal batteries (ASSLMBs), yet these desired properties are rarely achieved simultaneously. Here, in this work, it is noticed that the huge resistance at Li metal/electrolyte interface dominantly impeded the normal cycling of ASSLMBs especially at around room temperature (<30 °C). Accordingly, a supramolecular polymer ion conductor (SPC) with “weak solvation” of Li⁺ was prepared. Benefiting from the halogen-bonding interaction between the electron-deficient iodine atom (on 1,4-diiodotetrafluorobenzene) and electron-rich oxygen atoms (on ethylene oxide), the O-Li⁺ coordination was significantly weakened. Therefore, the SPC achieves rapid Li⁺ transport with high Li⁺ transference number, and importantly, derives a unique Li₂O-rich SEI with low interfacial resistance on lithium metal surface, therefore enabling stable cycling of ASSLMBs even down to 10 °C. This work is a new exploration of halogen-bonding chemistry in solid polymer electrolyte and highlights the importance of “weak solvation” of Li⁺ in the solid-state electrolyte for room temperature ASSLMBs.     

Room-Temperature Spin Transport in Metal Nanocluster-Based Spin Valves

As a new type of inorganic-organic hybrid semiconductor, quantum-confined atomically precise metal nanoclusters (MNCs) have been widely applied in the fields of chemical sensing, optical imaging, biomedicine and catalysis. Herein, we successfully design and fabricate the first example of MNC-based spin valves (SVs) that exhibit remarkable magnetoresistance (MR) value up to 1.6 % even at room temperature (300 K). The concomitant photoresponse of MNC-based SVs unambiguously confirms that the spin-polarized electron transmission takes place across the MNC interlayer. Furthermore, the spin-dependent transport property of MNC-based SVs is largely varied by changing the atomic structure of MNCs. Both experimental proofs and quantum chemistry calculations reveal that the atomic structure-discriminative spin transport behavior is attributed to the distinct spin-orbit coupling (SOC) effect of MNCs.     

基于界面热阻等效模型的超导磁体热输运分析

为解决直接冷却超导磁体中接触界面热阻造成的传热不连续问题,以实验数据为依据采用等效模型模拟接触界面热阻;基于有限元理论分析界面热阻对超导磁体热输运的影响;仿真结果表明等效模型的采用有助于解决低温下超导磁体接触界面间传热的不连续性问题,为研究高温超导磁体的热输运机理提供了一种新思路.     

Mg原子的嵌入对富勒烯C36的电子结构与传导特性的影响

采用基于密度泛涵理论的第一性原理和非平衡格林函数方法研究了Mg原子的嵌入对于C36 分子的电子结构及传导特性的影响．结果显示Mg原子的嵌入明显改变了C36分子的负微分电阻效应,且大大增强了C36 分子的电子传输性能．     

低压指数程序气相色谱薄涂柱的特性及应用

研究了一种新的低压指数程序气相色谱薄涂柱,确定了最佳的柱压、塔板高度、分离度及传质阻力系数等。结果表明,该柱具有操作柱压和柱温低、出峰速度快、分离效果好等特点,在分离多元醇样品时获得满意效果。     

光谱法研究闪电回击放电通道的电阻及电流的热效应

闪电放电通道的电阻及电流产生的热效应对雷电灾害研究以及防护设计都具有重要意义,放电通道的热力学特性与其等离子体辐射光谱密切相关。利用无狭缝摄谱仪获得的两次云对地多回击闪电放电的等离子体辐射光谱,依据谱线波长、强度等信息,结合同步地面电场变化资料,应用空气等离子体传输理论,计算了闪电回击放电通道的电导率、峰值电流、核心通道半径,进而得到了闪电回击等离子体通道单位长度的电阻、峰值电流时的热功率及在回击初始前5 μs内通道储存的热能。并与常规金属导体进行比较,分析了闪电回击放电在峰值电流时等离子体通道的热功率与电阻、电流平方之间的相关性关系。结果表明：利用光谱研究得到的闪电放电通道的电阻为0.04～8.41 Ω·m-1、峰值电流时的热功率为0.88×108～2.20×108 W·m-1、回击初始前5 μs内通道储存的热能为1.47×102～3.66×102 J·m-1,以上结果与文献报道的利用其他方法得到的结果相比,在合理的范围内;与常规金属导体相比,闪电回击放电等离子体通道在峰值电流时的热功率与电阻成正比,但与电流的平方呈指数减小的关系;由于闪电等离子体通道的电阻与温度的3/2次方成反比,通常回击放电通道中峰值电流越大,通道温度越高,而电阻会迅速降低,因此热功率也会急剧减小。此结论进一步验证了采用欧姆加热方法加热等离子体的致命缺点。     

Numerical analysis of respiratory flow patterns within human upper airway

A computational fluid dynamics （CFD） approach is used to study the respiratory airflow dynamics within a human upper airway. The airway model which consists of the airway from nasal cavity, pharynx, larynx and trachea to triple bifurcation is built based on the CT images of a healthy volunteer and the Weibel model. The flow character- istics of the whole upper airway are quantitatively described at any time level of respiratory cycle. Simulation results of respiratory flow show good agreement with the clinical mea- sures, experimental and computational results in the litera- ture. The air mainly passes through the floor of the nasal cavity in the common, middle and inferior nasal meatus. The higher airway resistance and wall shear stresses are distrib- uted on the posterior nasal valve. Although the airways of pharynx, larynx and bronchi experience low shear stresses, it is notable that relatively high shear stresses are distrib- uted on the wall of epiglottis and bronchial bifurcations. Besides, two-dimensional fluid-structure interaction models of normal and abnormal airways are built to discuss the flow-induced deformation in various anatomy models. The result shows that the wall deformation in normal airway is relatively small.     

Collapse of quantized Hall resistance and breakdown of dissipationless state in the integer quantum Hall effect: filling factor dependence

Magnetic field dependence of critical current for collapse of quantized Hall resistance I_cr(collapse) and critical current for breakdown of dissipationless state I_cr(breakdown) have been measured near the filling factor ν=4 of Landau levels in a GaAs/AlGaAs heterostructure Hall bar. The difference I_cr(breakdown)−I_cr(collapse) decreases against the increase and the decrease in ν from 4 and the critical behavior disappears outside of the region 3.85<ν<4.15.     

膜电阻对自组装膜修饰电极电化学行为的影响

应用循环伏安和交流阻抗技术研究了 16烷基硫醇自组装膜修饰的金电极在Fe(CN) 63 - /Fe(CN) 64 - 溶液中的电化学行为 .无“针孔”缺陷的自组装膜对溶液与基底间的界面电子转移具有强烈的阻碍作用 ,当过电位较大时 ,In(I/ η)对 η1/2 之间具有良好的线性关系 .通过对Au/SAM /Hg模拟体系的电流———电压曲线进行测定 ,得到了自组装膜膜电阻的特征 .指出由于膜电阻的存在 ,自组装膜修饰电极在Fe(CN) 63 - /Fe(CN) 64 - 溶液中的行为实质上反映了膜自身的电阻特征