Preparations and Electrocatalytic Ethanol Properties of Palladium Intercalated Hydrotalcite

高性能的电催化剂对直接燃料电池的商业化应用有着至关重要的作用,目前的阳极材料还存在活性低、易中毒、成本高等问题。本研究以层状双氢氧化物(layered double hydroxides, LDHs)为载体通过浸渍法制备了新型纳米钯(Pd)催化剂,并通过X射线衍射仪、扫描电子显微镜、电感耦合等离子体质谱仪、能谱仪、透射电子显微镜、循环伏安法测试、计时电流测试和电化学阻抗等方法对催化剂的结构和电催化性能进行了研究。结果表明,新制备的Pd/Mg-Al-LDHs仍然保持着LDHs的层状结构,循环伏安测试表明在碱性条件下,Pd/Mg-Al-LDHs比Pd/C有更好的电催化乙醇活性和抗中间产物中毒性能,且乙醇浓度、扫描速率和温度等因素对峰电流有着直接影响。计时电流测试表明在电催化乙醇的过程中Pd/Mg-Al-LDHs比Pd/C拥有更高的电催化活性和稳定性。电化学阻抗测试表明,Pd插层可显著改善Mg-Al-LDHs的导电性,并降低电催化过程中电荷转移阻力。High-performance electrocatalysts play a vital role in the commercial application of direct fuel cells. Current anode materials still have such problems as low activity, easy poisoning and high cost. In this study, a new type of nano- palladium (Pd) catalyst was prepared by dipping method using layered double hydroxides (LDHs) as the carrier. X-ray diffractometer, scanning electron microscope (SEM), inductively coupled plasma mass spectrometer (ICP-MS), energy spectrometer, transmission electron microscope (TEM), cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscope were used to analyze the structure and electrocatalytic performance of the catalyst. The results showed that the newly prepared Pd/Mg-Al-LDHs still maintained the layered structure of LDHs, and the metal Pd was evenly dispersed between the layers of hydrotalcite. Cyclic voltammetric curves showed that under alkaline conditions, the peak current density of Pd/Mg-Al-LDHs with 7% Pd in electrocatalytic ethanol was 36 mA·cm-2. The peak current density of commercial Pd/C in electrocatalytic ethanol was 30 mA·cm-2, and Pd/Mg-Al-LDHs exhibited better resistance to intermediate product poisoning. The factors including ethanol concentration, scanning rate and temperature were found to be effective, in particular, peak current had a direct effect. The chronoamperometric test revealed that Pd/Mg-Al-LDHs displayed higher electrocatalytic activity and stability toward ethanol than Pd/C, and the current density of Pd/Mg-Al-LDHs at 2000 s was 12 times to that of the commercial Pd/C. The electrochemical impedance data showed that Pd intercalation could significantly improve the conductivity of Mg-Al-LDHs and reduce the resistance to charge transfer during the electrocatalytic process.国家自然科学基金项目(51208299)通讯作者:李亮E-mail:[email protected]:LiangLiE-mail:[email protected]上海理工大学环境与建筑学院,上海 200093School of Environment and Architecture,University of Shanghai for Science and Technology, Shanghai 200093, Chin

Transition from tunneling leakage current to molecular tunneling in single-molecule junctions

数十年来，半导体工业一直遵循基于“摩尔定律”所设定的发展蓝图，逐步提升集成电路芯片上晶体管的集成度和运行速度，减小器件尺寸。为探索这一尺寸极限，课题组基于机械可控裂结技术自主开发了具有飞安级电学测量和亚纳米级位移控制灵敏度的科学仪器，在国际上首次获取了一系列具有不同重复单元的寡聚苯乙炔类分子电导随电极间距的演变关系，并发现随着电极间距的缩小，器件电输运由通过分子器件电流占主导逐步转变到由隧穿漏电流占主导。对于本研究中具有最小尺寸的寡聚苯乙炔分子器件，其由于隧穿漏电流所制约的尺寸极限可小至0.66 nm，预示了有机分子器件在未来电子器件小型化方面具有重要的应用潜力。 这一研究工作是在化学化工学院洪文晶教授、萨本栋微纳研究院杨扬助理教授以及英国Durham University的MartinR. Bryce教授共同指导下完成的。能源材料化学协同创新中心iChEM Fellow刘俊扬博士为论文第一作者，博士研究生郑珏婷、李瑞豪和硕士研究生黄晓艳、唐永翔、皮九婵、本科生王飞等参与了研究工作。田中群教授、毛秉伟教授和师佳副教授为论文工作提供了重要指导。【Abstract】The tunneling leakage current will be a major quantum obstacle during miniaturization in the semiconductor industry down to the scale of several nanometers. At this scale, to promote charge transport and overcome the tunneling leakage current between the source and drain terminals, molecular electronic junctions offer opportunities by inserting molecules between these two electrodes. Employing a series of oligo(aryleneethynylene) (OAE) molecules, here we investigate the transition from tunneling leakage current to molecular tunneling in the single-molecule devices using mechanically controllable break junction (MCBJ) technique, and the transition distances of the OAE molecular junctions were determined and even down to 0.66 nm for OAE2 molecular junction, which demonstrates that the intrinsic charge transport properties of a single-molecule device can be outstripped from the tunneling leakage current. Consequently, molecular electronic devices show the potential to push the ultimate limit of miniaturization to the scale of several angstroms.This work was supported by the National Key R&D Program of China (2017YFA0204902). This work was also generously supported by the Young Thousand Talent Project of China, the EC FP7 ITN “MOLESCO” project number 606728, the National Natural Science Foundation of China (nos. 21703188, 21673195, 21503179), and the China Postdoctoral Science Foundation (2017M622060). 该工作获得科技部国家重点研发计划课题（2017YFA0204902），国家自然科学基金委（21673195、21703188、21503179）以及中国博士后科学基金（2017M622060）等项目的资助，也得到了固体表面物理化学国家重点实验室、能源材料化学协同创新中心的支持

Electric-field-induced selective catalysis of single-molecule reaction

随着单分子电学检测技术的迅速发展，分子电子学的研究不再局限于分子电子学器件的构筑及其电学性质的测量，而且扩展到单分子尺度化学反应过程的探索。然而目前相关的研究仍然局限于理论计算方面，在单分子尺度上实时监测和调控化学反应的活性和选择性是化学领域的长期目标和挑战。针对这一挑战，洪文晶教授课题组与程俊教授课题组合作，自主研发了精密科学仪器，将单个有机分子定向连接在两个末端尺寸为原子级的电极之间，解决了化学反应中分子取向控制的问题.理论计算结果证实了定向电场可以有效地稳定化学反应的过渡态，从而降低反应能垒。该研究工作在化学化工学院洪文晶教授、程俊教授、能源材料化学协同创新中心（iChEM）刘俊扬副研究员的共同指导下完成，由硕士研究生黄晓艳、iChEM博士研究生唐淳、博士研究生李洁琼以及兰州大学的陈力川博士作为共同第一作者，化学化工学院师佳副教授、陈招斌高级工程师、夏海平教授和田中群教授，萨本栋微纳研究院杨扬副教授、环境与生态学院白敏冬教授以及兰州大学张浩力教授参与了研究工作的讨论并给予指导，博士后乐家波、博士研究生郑珏婷、张佩（已毕业）、李瑞豪、李晓慧也参与了研究工作。Oriented external electric fields (OEEFs) offer a unique chance to tune catalytic selectivity by orienting the alignment of the electric field along the axis of the activated bond for a specific chemical reaction; however, they remain a key experimental challenge. Here, we experimentally and theoretically investigated the OEEF-induced selective catalysis in a two-step cascade reaction of the Diels-Alder addition followed by an aromatization process. Characterized by the mechanically controllable break junction (MCBJ) technique in the nanogap and confirmed by nuclear magnetic resonance (NMR) in bottles, OEEFs are found to selectively catalyze the aromatization reaction by one order of magnitude owing to the alignment of the electric field on the reaction axis. Meanwhile, the Diels-Alder reaction remained unchanged since its reaction axis is orthogonal to the electric fields. This orientation-selective catalytic effect of OEEFs reveals that chemical reactions can be selectively manipulated through the elegant alignment between the electric fields and the reaction axis.This work was supported by the National Key R&D Program of China (2017YFA0204902), the National Natural Science Foundation of China (21722305, 21703188, 21673195, 21621091, 51733004, 51525303, and 91745103), the China Postdoctoral Science Foundation (2017M622060), and the Young Thousand Talents Project of China. 该工作得到国家自然科学基金委（21722305、21703188、21673195、51733004、51525303、91745103），国家重点研发计划课题（2017YFA0204902），中国博士后面上基金（2017M622060）的资助，以及固体表面物理化学国家重点实验室、醇醚酯化工清洁生产国家工程实验室、能源材料化学协同创新中心的支持

超高转速齿轮箱轴承-转子系统性能分析及优化设计研究

以可倾瓦轴承-转子系统为基础，仿真计算分析了轴承跨距、轴径及轴承相关参数对轴承-转子系统临界转速的影响，为高速齿轮箱轴承-转子的优化设计提供依据。研究表明，跨距的影响与转速关系密切；轴径超过54 mm后，影响可忽略；间隙比、支点偏移及预负荷系数对1阶、2阶临界转速的影响趋势基本相同，关系曲线分别为线性、对数和指数形式。根据分析结果，设计了60 000 r/min齿轮箱，轴承-转子系统通过空载试验，齿轮箱整体性能满足要求

高速转子用非接触式迷宫密封的密封性能影响因素研究

为了提高高速齿轮箱密封装置的密封性能，对常用于石油、化工等领域中的高速齿轮传动装置的非接触式迷宫密封进行了分析。通过建立（Computational fluid dynamics，CFD）数值计算模型，分析了该密封装置的密封齿数量、密封压差、油气混合物浓度、甩油环位置等因素对各密封腔回油口回油量及漏油口泄漏量的影响。研究对高速齿轮箱用非接触式迷宫密封的设计具有指导意义

Protonation Tuning of Quantum Interference in Azulene-Type Single-Molecule Junctions

单分子尺度电输运性质的研究为从分子水平计分子材料和器件提供了直接实验依据。在单分子尺度，因电子不同传输路径引起的量子干涉效应对单分子尺度电输运性质有显著影响，而如何有效调控量子干涉效应从而控制分子器件电输运性质仍然是分子电子学领域重大挑战之一。在该项研究工作中，通过对奥甘菊系列分子单分子尺度电输运性质研究发现，5,7位取代的奥甘菊电输运能力低于其他取代位点奥甘菊分子，存在明显的相消量子干涉效应。奥甘菊系列分子作为刺激响应结构单元在未来分子器件和材料中有重要的应用前景，同时基于质子化地量子干涉效应调控也为单分子器件电输运性质的未来设计提供了新思路。 这一跨学科研究工作是在我院洪文晶教授、中科院化学所张德清研究员及刘子桐副研究员、英国Lancaster大学Colin Lambert教授的共同指导下完成的。我院2014级硕士研究生杨国钢、英国Lancaster大学物理系博士后Sara Sangtarash博士作为共同第一作者，我院研究生李晓慧、谭志冰、李瑞豪、郑珏婷等共同完成，师佳副教授、刘俊扬特任副研究员和微纳院杨扬助理教授也参与了部分研究工作。【Abstract】The protonation of azulene derivatives with quantum interference effects is studied by the conductance measurements of single-molecule junctions. Three azulene derivatives with different connectivities are synthesized and reacted with trifluoroacetic acid to form the protonated states. It is found that the protonated azulene molecular junctions produce more than one order of magnitude higher conductance than the neutral states, while the molecules with destructive interference show more significant changes. These experimental observations are supported by our recently-developed parameter free theory of connectivity, which suggests that the largest conductance change occurs when destructive interference near the Fermi energy in the neutral state is alleviated by protonation.这一工作得到了国家重点研发计划（2017YFA0204902）、自然科学基金项目（21673195，21190032，21372226，21503179）、千人计划青年项目、固体表面物理化学国家重点实验室、能源材料化学协同创新中心（2011-iChEM）以及石墨烯工程与产业研究院的支持

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编辑和翻译: 姜海日、巫靓、中山大将、福谷彬、趙偵宇、郭玫珂、楊維

大连极紫外相干光源

先进光源的发展在前沿科学研究中发挥的作用越来越重要。近十年来,飞速发展的自由电子激光技术为科学家们提供了探索未知世界、发现新科学规律和实现技术变革的重要工具。建成的大连极紫外(EUV)相干光源的运行波段为50~150nm,单脉冲能量大于100μJ,且可提供10-12 s和10-13 s量级的超快激光脉冲,是我国第一台自由电子激光用户装置,并且是国际上唯一运行在极紫外波段的自由电子激光用户装置,在世界范围内为用户提供具有高峰值亮度和超短脉冲的极紫外激光。大连EUV相干光源是由国家自然科学基金委资助、由中国科学院大连化学物理研究所和上海应用物理研究所共同承担的重大科学仪器研制项目,目标是打造一个以先进极紫外光源为核心、主要用于能源基础科学研究的光子科学平台

JUNO Sensitivity on Proton Decay p→νˉK+p\to \bar\nu K^+ Searches

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this paper, the potential on searching for proton decay in $p\to \bar\nu K^+$ mode with JUNO is investigated.The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits to suppress the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar\nu K^+$ is 36.9% with a background level of 0.2 events after 10 years of data taking. The estimated sensitivity based on 200 kton-years exposure is $9.6 \times 10^{33}$ years, competitive with the current best limits on the proton lifetime in this channel