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专访中国石墨烯领军人物:刘忠范院士及他的团队
《物理化学学报》编辑部
2019, 35(8): 787-791  doi: 10.3866/PKU.WHXB201904035
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亮点
离子液体独特的催化性能:无金属条件下氢键催化醇氧化酯化生成酯
刘志敏
2019, 35(8): 792-793  doi: 10.3866/PKU.WHXB201810031
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金属与碳化物载体间强相互作用(SMSI)研究
马丁
2019, 35(8): 794-795  doi: 10.3866/PKU.WHXB201810033
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Au144的单晶结构获得解析
郑兰荪
2019, 35(8): 796-797  doi: 10.3866/PKU.WHXB201810066
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人源蛋白酶体底物降解动力学的高分辨三维冷冻电子成像
刘鸣华
2019, 35(8): 798-799  doi: 10.3866/PKU.WHXB201812002
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单分子研究揭示无定形红磷的确切分子结构
吴凯
2019, 35(8): 800-801  doi: 10.3866/PKU.WHXB201901024
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HCO自由基光解反应中的动态干涉
杨金龙
2019, 35(8): 802-803  doi: 10.3866/PKU.WHXB201901030
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当期推荐
探索氟代碳酸乙烯酯添加剂对钠离子电池正极的影响
刘忠范
2019, 35(8): 804-805  doi: 10.3866/PKU.WHXB201903013
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基于裂结技术的单分子化学反应研究进展综述
迟力峰
2019, 35(8): 806-807  doi: 10.3866/PKU.WHXB201903025
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通讯
原位液体室透射电镜观察金纳米棒/石墨烯复合物的形成和运动过程
方佳丽, 陈新, 李唱, 吴玉莲
2019, 35(8): 808-815  doi: 10.3866/PKU.WHXB201901035
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本文利用原位液体室透射电子显微镜实时观察了液态下金纳米棒/石墨烯复合物的动态自组装行为。结果表明,由于电荷吸引力,金纳米棒倾向于通过尖端接近方式靠近石墨烯的边缘。组装结构形成以后,金纳米棒与石墨烯边缘可以发生相对旋转,其中金纳米棒边缘贴合石墨烯边缘的结构更稳定,并且没有显示金纳米棒与石墨烯边缘之间的相对角度随时间的变化。观察到了自组装结构的漂移运动,与较小尺寸的自组装结构相比,较大尺寸的结构显得更难以通过液体流动推动运动,并且其运动更容易因为来自液体室窗口基底的阻力而慢下来。利用液体室透射电镜进一步观察石墨烯折叠结构,观察结果表明折叠结构可随时间在液体中打开和闭合,导致固定在石墨烯层上的金纳米棒表现出与石墨烯之间的明显相对位置变化。总体上,自组装结构非常稳定,并且在液体中没有表现出任何的分离行为。进一步,将金纳米棒/石墨烯复合物用作催化剂,在4-硝基苯酚催化还原实验中显示出比单纯金纳米棒更好的催化性能。投料质量比为1 : 5的金纳米棒/石墨烯复合物表现出最佳性能,表观速率常数值为0.5570 min−1,是单纯金纳米棒的8倍。这一显著改善与优化稳定的金纳米棒/石墨烯复合物结构密切相关。原位液体室透射电镜为分析液体中复杂的自组装行为,及未来的高性能复合催化剂材料的开发,提供了一种强有力的表征方法。
综述
表面活性剂溶胀胶束:性能及应用
龚铃堰, 廖广志, 陈权生, 栾和鑫, 冯玉军
2019, 35(8): 816-828  doi: 10.3866/PKU.WHXB201810060
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溶胀胶束是表面活性剂胶束增溶其它物质后使胶束膨胀的一种胶束状态,因其能显著提高难溶性物质的溶解度而备受关注。针对近年来对溶胀胶束的研究进展,综述了溶胀胶束的最大增溶量、增溶过程以及增溶后形貌尺寸的变化等问题,总结了影响胶束增溶作用的因素,厘清了溶胀胶束与微乳液的异同,介绍了溶胀胶束的应用,展望了其应用前景与发展方向。
基于裂结技术的单分子尺度化学反应研究进展
余培锴, 冯安妮, 赵世强, 魏珺颖, 杨扬, 师佳, 洪文晶
2019, 35(8): 829-839  doi: 10.3866/PKU.WHXB201811027
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分子电子学是研究单分子器件的构筑、性质以及功能调控的一门新兴学科。其中,金属/分子/金属结的构筑和表征是现阶段分子电子学的主要研究内容。裂结技术是当前分子电子学研究的主要实验方法,主要包括机械可控裂结技术和扫描隧道显微镜裂结技术。本文对裂结技术进行了介绍,并对近年来利用这些技术,在单分子尺度化学反应的检测和动力学研究,以及将这些技术与溶液环境、静电场、电化学门控等方法相结合,调控单分子器件的电输运性质等方面所取得的进展进行了概述。
ARTICLE
Concentration Dependent Effects of Ca2+ and Mg2+ on the Phosphatidylethanolamine-Phosphatidylglycerol Bilayer
Tao ZHANG, Yunguang QIU, Qichao LUO, Xi CHENG, Lifen ZHAO, Xin YAN, Bo PENG, Hualiang JIANG, Huaiyu YANG
2019, 35(8): 840-849  doi: 10.3866/PKU.WHXB201811016
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Ca2+ and Mg2+ ions are the main divalent cations in living cells and play vital roles in the structure and function of biological membranes. To date, the differences in the effects of these two ions on the Escherichia coli (E. coli) inner membrane at various concentrations remain unknown. Here, the effects of Ca2+ and Mg2+ ions on a mixed lipid bilayer composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol (POPG) in a 3 : 1 ratio (mol/mol), which mimics the E. coli inner membrane, were quantitatively differentiated at different concentrations by dynamic light scattering (DLS), zeta potential measurements and all-atom molecular dynamics (AA-MD) simulations. The DLS results demonstrated that the POPE/POPG liposomes were homogeneous and monodisperse in solutions with Ca2+ or Mg2+ ion concentrations of 0 and 1 mmol∙L-1. As the Ca2+ or Mg2+ ion concentration was increased to 5-100 mmol∙L-1, lipid aggregation or the fusion of unilamellar liposomes occurred in the ion solutions. The zeta potential measurements showed that both the Ca2+ and Mg2+ ions had overcharging effects on the negatively charged POPE/POPG liposomes. The AA-MD simulation results indicated that the Ca2+ ions irreversibly adsorbed on the membranes when the simulation time was longer than 100 ns, while the Mg2+ ions were observed to dynamically adsorb on and desorb from the membranes at various concentrations. These results are consistent with the DLS and zeta potential experiments. The average numbers of Ca2+ and Mg2+ ions in the first coordination shell of the oxygen atoms of the phosphate, carbonyl and hydroxyl groups of POPE and POPG (i.e., the first coordination numbers) in the pure membrane and membranes containing 5 and 100 mmol∙L-1 ions were calculated from the radial distribution functions. The results indicated that the primary binding site of these two ions on POPE and POPG at the concentrations studied was the negatively charged phosphate group. Thus, these results might explain the overcharging effects of both the Ca2+ and Mg2+ ions on the POPE/POPG liposomes. Moreover, as the Ca2+ concentration increased, the area per lipid of the lipid bilayers decreased, and the membrane thickness increased, while the Mg2+ ions had negligible effects on these membrane parameters. In addition, these ions had different effects on the orientation of the lipid head groups. These simulation results may be used to provide the possible explanations for the differences between Ca2+ and Mg2+ ions in DLS and zeta potential measurements at the atomic level. The experimental results and MD simulations provide insight into various biological processes regulated by divalent cations, such as membrane fusion.
Tunable Reactivity of MNi12 (M = Fe, Co, Cu, Zn) Nanoparticles Supported on Graphitic Carbon Nitride in Methanation
Mengru HAN, Yanan ZHOU, Xuan ZHOU, Wei CHU
2019, 35(8): 850-857  doi: 10.3866/PKU.WHXB201811040
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As a unique two-dimensional material, graphitic carbon nitride (g-C3N4) has received significant attention for its particular electronic structure and chemical performance. Its instinctive defect can provide a stable anchoring site for metals, potentially improving the surface reactivity. Ni-based catalysts are economical but their activity for CO2 methanation is lower than that of noble metal catalysts. Ni nanoparticles (NPs) supported on a substrate can further enhance the stability and activity of catalysts. Based on the principles of strong metal-support interaction (SMSI) and the synergistic effect on an alloy, MNi12/g-C3N4 composites as novel catalysts are expected to improve stability and catalytic performance of Ni-based catalysts. The configurations are established with core-shell structures of MNi12 (M = Fe, Co, Cu, Zn) nanoparticles (NPs) supported on g-C3N4 in this work. In the CO2 methanation reaction, the reactivity of CO on slab (ECO) is a critical factor, which is relative to the catalytic activity. Thus, the catalytic reactivity of these complexes via CO adsorption were explored using density functional theory (DFT). The values of cohesive energy (Ecoh) for MNi12 NPs range from -39.90 eV to -34.82 eV, suggesting that the formation of these NPs is favored as per thermodynamics, and Ecoh and partial density of state (PDOS) reveal that the central M atom with the less filled d-shell interacts more strongly with surface Ni atoms. Therefore, ZnNi12 is the most unstable structure among all the studied alloy, and the synergistic effect is also the weakest among them. When MNi12 NPs are supported on the g-C3N4 substrate, the binding energies (Eb) vary from -9.40 eV to -8.39 eV, indicating that g-C3N4 is indeed a good material for stabilizing these NPs. The PDOS analysis of pure g-C3N4 suggests the sp2 dangling bonds of N atoms in g-C3N4 can stabilize these transition metal NPs. Furthermore, the results of CO adsorbed on MNi12 NPs and MNi12/g-C3N4 composites show that ECO and dCO reduced with the introduction of g-C3N4. According to the results of the analysis of the Hirshfeld charges and electrostatic potential (ESP), the reason is that CO obtains less electrons from MNi12 NPs after deposition on the g-C3N4 substrate, which lowers the reactivity of CO on catalysts. Additionally, the deformation charge density is analyzed to investigate the interaction between the NPs and g-C3N4. With the introduction of g-C3N4, charge redistribution indicates the strong metal-support interaction, which further reduces the CO adsorption energy. In summary, MNi12 supported on g-C3N4 exhibit not only high stability but also tunable reactivity in CO2 methanation. These changes are beneficial for CO2 methanation reaction.
论文
定常冲击波作用下六硝基六氮杂异伍兹烷(CL-20)/奥克托今(HMX)含能共晶初始分解机理研究
刘海, 李毅, 马兆侠, 周智炫, 李俊玲, 何远航
2019, 35(8): 858-867  doi: 10.3866/PKU.WHXB201812011
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采用ReaxFF分子动力学方法同时结合多尺度冲击技术(MSST)模拟了4-10 km·s-1定常冲击波加载下含能共晶CL-20/HMX沿不同晶格矢量的初始物理化学响应。获得了系统温度、压力、密度以及粒子速度的时间演化路径,以及初始分解路径,最终稳定反应产物和冲击雨贡纽等。研究结果表明:冲击波入射至含能共晶后,物理上依次经历诱导期、快压缩、慢压缩以及膨胀过程。快压缩和慢压缩过程分别对应反应物的快分解和慢分解。采用指数函数对反应物的衰减曲线进行拟合,并比较了共晶中反应物的衰减速率。整体上,随着冲击波速度的增加,反应物响应的时间逐渐提前,并且,冲击波沿各晶格矢量入射后,共晶中CL-20分子分解的响应时间均早于HMX。CL-20快分解阶段的衰减速率最高,HMX快分解的衰减速率居其次。相对于快分解阶段,慢分解阶段各反应物的衰减速率差异较小。含能共晶的初始反应路径是CL-20聚合形成二聚体,而冲击诱导共晶分解的初始反应路径是CL-20中N-NO2键断裂形成NO2。随后产生N2O,NO,HONO,OH,H等中间小分子。最终稳定产物是N2,H2O,CO2,CO和H2。晶格矢量bc方向冲击感度相同,低于晶格矢量a方向的感度。冲击诱导共晶中CL-20和HMX分解的最小冲击波速度(us)分别为6 km·s-1和7 km·s-1。采用冲击雨贡纽关系计算得到沿晶格矢量abc冲击诱导CL-20/HMX共晶起爆的压力分别为16.52 GPa,17.41 GPa和17.41 GPa。爆轰压力范围介于36.75 GPa-47.43 GPa。
氟代碳酸乙烯酯添加剂对钠离子电池正极的影响
程振杰, 毛亚云, 董庆雨, 金锋, 沈炎宾, 陈立桅
2019, 35(8): 868-875  doi: 10.3866/PKU.WHXB201811033
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使用电解液成膜添加剂是一种简单高效的提高电池循环稳定性的方法。氟代碳酸乙烯酯(FEC)的最低未被占据分子轨道(LUMO)能量较低,易被还原,通常被认为是很好的负极成膜添加剂,但因其最高占据分子轨道(HOMO)能量也较低,抗氧化性较好,故其被认为不在正极上发生作用。本工作结合电化学,形貌分析,化学成分表征,原位结构分析等方法研究了FEC添加剂在钠离子电池中的作用。我们发现适量的FEC添加剂不仅可以显著抑制电解液溶剂碳酸丙烯酯(PC)的分解,而且会在正极上形成一层富NaF的保护层,提高循环过程中正极晶格结构稳定性,从而提高电池的循环稳定性。密度泛函理论(DFT)计算表明,FEC之所以能在正极上形成保护层,可能与其容易在正极界面与钠盐阴离子ClO4-结合反应有关。
用于药物载体的多重响应型聚合物分子的设计与合成
王义洲, 刘晔宏, 徐首红, 刘洪来
2019, 35(8): 876-884  doi: 10.3866/PKU.WHXB201901019
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利用原子转移自由基聚合(ATRP)法和连续ATRP法合成了温度敏感型聚合物和pH/温度双重敏感型聚合物。用紫外光谱考察聚合物在水溶液中的温敏行为,发现聚合物的低临界溶解温度(LCST)可以通过单体的比例进行调控,而且聚合物的温度响应行为非常敏感且具有可逆性。pH/温度双重敏感型聚合物还具有非常灵敏的pH响应行为,且不受单体比例的影响。最后,对聚合物胶束的体外释药动力学进行了研究,结果表明聚合物胶束的环境敏感性决定了药物的释放行为。
C60与MoO3混合材料做空穴注入层的单层有机电致发光器件
薛楷, 闫敏楠, 潘飞, 田梦颖, 潘旭东, 张宏梅
2019, 35(8): 896-902  doi: 10.3866/PKU.WHXB201810064
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我们制备研究了基于结构为氧化铟锡(ITO)/C60 (1.2 nm):MoO3 (0.4 nm)/1, 3, 5-三(1-苯基-1H-苯并咪唑-2-基)苯(TPBi):三(2-苯基吡啶)铱[Ir(ppy)3] (33%,90 nm)/LiF (0.7 nm)/Al (120 nm)的高效绿色磷光单层有机发光二极管(OLED)。分别将C60,MoO3与C60:MoO3混合物作为空穴注入层(HIL)作为对比。TPBi在发光层中起着主体以及电子传输材料的双重作用。在使用电子传输型主体的单层OLED中,空穴注入层性质对于调节电子/空穴注入以获得电荷载流子传输平衡起重要作用。因此,适当调节空穴注入层是实现高效单层OLED的关键因素。由于MoO3较大的电子亲和能(6.37 eV)会诱导电子从C60的最高占据分子轨道(HOMO)能级转移至MoO3,从而形成C60阳离子,并使得Mo元素的价态从+6降至+5,C60:MoO3混合就可以较好的调节空穴注入性质。最终实现最大电流效率为35.88 cd∙A−1的单层有机发光器件。
Article
Preparation of Defective TiO2-x Hollow Microspheres for Photocatalytic Degradation of Methylene Blue
Jiawei ZHANG, Sheng WANG, Fusheng LIU, Xiaojie FU, Guoquan MA, Meishun HOU, Zhuo TANG
2019, 35(8): 885-895  doi: 10.3866/PKU.WHXB201812022
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In recent years, photocatalytic degradation of organic pollutants has attracted considerable attention because of its potential application for solving environmental problems. Among various semiconductor photocatalysts, TiO2 is considered a promising candidate due to its excellent structural stability. Many researchers have focused on improving the visible-light catalytic efficiency of TiO2, because the large band gap of TiO2 limits its utilization of visible light energy. Recently, it has been proved that intrinsic defects like oxygen vacancies in TiO2 can trigger the visible light activity. TiO2 hollow microspheres with large surface areas have shown high photocatalytic efficiencies in the degradation of organic pollutants. To date, the photocatalytic performance of TiO2-x hollow microspheres has not been investigated. The kinetics of photocatalytic degradation of organic dyes is usually depicted by the pseudo-first-order kinetic equation. However, a few studies have demonstrated the impact of light absorption by the dye itself on photocatalytic performance in terms of the rate equation. In this study, defective TiO2-x hollow microspheres were prepared by the hydrogen reduction process to effectively promote photocatalytic activity under visible light irradiation. The structure and properties were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis, X-ray photoelectron spectroscopy (XPS), electron spin-resonance (ESR), Raman spectrometry, ultraviolet-visible diffuse-reflectance spectroscopy (UV-Vis DRS), and electrochemical tests. The photocatalytic performance was evaluated based on the photocatalytic degradation of methylene blue (MB) solution under visible light irradiation. The mechanism underlying the enhancement of photocatalytic activity was also discussed. The results show that the visible-light photocatalytic activity of TiO2-x, and TiO2-x hollow microsphere benefit from the presence of oxygen vacancies on the surface. The photocatalytic activity of TiO2-x hollow microspheres is better than that of TiO2-x, attributed to the formation of hollow structures with higher specific surface areas. The mechanism of MB degradation occurring on the TiO2-x hollow microsphere surface was also investigated. The results show that the MB molecules are photodegraded by the photogenerated hole (h+), reactive superoxide radical (•O2-), and hydroxyl radicals (•OH), and that the •OH radicals, produced only by photogenerated holes, play an essential role in the degradation of MB. Based on the discussion of the effect of initial concentration of MB on the degradation process, a new kinetic model was proposed for the photocatalytic degradation of dye, considering the effect of visible light absorbed by MB molecules, because the data estimated by pseudo-first-order kinetic equation do not fit well with the experimental data. The Runge-Kutta method was used to obtain the numerical solution of the kinetic model. The results show that the kinetic model proposed for photocatalytic dye degradation gives a more realistic description of the photocatalytic degradation of MB because the calculated results fit better with the experimental data. The rate constant (kapp) of the pseudo-first-order kinetic equation decreases with increasing initial concentration of MB, indicating that kapp is affected by the light absorption properties of MB, because an increase in the initial concentration of MB will lead to increased absorption of visible light by MB molecules rather than by TiO2-x hollow microsphere. Unlike the rate constant kapp, the rate constant ka in the proposed model describes the process of photocatalytic dye degradation more effectively because it does not depend on the initial dye concentration.

亮点
同分异构的胶体硫化镉半导体幻数团簇的可逆转化
刘忠范
2019, 35(5): 451-452  doi: 10.3866/PKU.WHXB201807016
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异原子占据Ag原子簇的中心核用于催化CO2生成碳碳键的反应
侯文华
2019, 35(5): 453-454  doi: 10.3866/PKU.WHXB201807017
[摘要]  (78) [HTML全文] (78) [PDF 659KB] (78)
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基于Au@PPy核壳结构纳米粒子自组装阵列的可程序化负微分电阻效应研究
韩布兴
2019, 35(5): 455-456  doi: 10.3866/PKU.WHXB201807063
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摘要:
当期推荐
弛豫时间分布法分解固体氧化物燃料电池电化学阻抗谱
庄林
2019, 35(5): 457-458  doi: 10.3866/PKU.WHXB201807065
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摘要:
电荷驱动水中氧化物纳米颗粒自组装的原位透射电子显微镜研究
吴凯
2019, 35(5): 459-460  doi: 10.3866/PKU.WHXB201807077
[摘要]  (87) [HTML全文] (87) [PDF 250KB] (87)
摘要:
综述
有机太阳能电池中基于苝二酰亚胺结构小分子受体进展
邓祎华, 彭爱东, 吴筱曦, 陈华杰, 黄辉
2019, 35(5): 461-471  doi: 10.3866/PKU.WHXB201806073
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摘要:
最近几年,有机太阳能电池中的非富勒烯小分子受体研究引起了人们的兴趣。其中,苝二酰亚胺(PDI)类分子因具有良好的电子传输能力,较强的电子亲和力,稳定的光、热、化学性能以及化学结构的可设计性带来的性能可调控性而得到广泛的关注。本文总结了近三年来在体异质结有机太阳能电池应用方面PDI小分子受体的研究进展,重点关注了PDI分子结构对其性能的影响,希望为以后PDI类受体分子的设计思路起到一定的启发作用。
碳基非贵金属氧还原电催化剂的活性位结构研究进展
杨晓冬, 陈驰, 周志有, 孙世刚
2019, 35(5): 472-485  doi: 10.3866/PKU.WHXB201806131
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摘要:
以热解型Fe/N/C为代表的碳基非贵金属材料被认为是当前最具潜力替代铂的非贵金属氧还原催化剂,其综合性能的进一步突破,对于推动质子交换膜燃料电池商业化应用具有重要意义。对热解型Fe/N/C催化剂活性位结构的深入认识是实现催化剂高活性位密度和高稳定性理性设计的关键。本文总结了热解型Fe/N/C活性位的研究进展,重点介绍了非晶态铁氮配位活性中心、氮掺杂和碳缺陷三类活性位构型。由于热解型Fe/N/C是非均相的,结构非常复杂,导致在活性位认识上还存在诸多争议,本文总结阐述了活性位结构的不同观点。最后,我们展望了Fe/N/C催化剂活性位研究的未来方向。
论文
正十二烷高温机理简化及验证
卢海涛, 刘富强, 王于蓝, 王成冬, 范雄杰, 刘存喜, 徐纲
2019, 35(5): 486-495  doi: 10.3866/PKU.WHXB201806081
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摘要:
由于详细化学反应机理在模拟燃烧室燃烧时,计算量极大,很难被广泛运用。为了满足工程设计要求,采用替代燃料的简化机理进行计算不失为一种行之有效的方法。本文基于误差传播的直接关系图法和敏感性分析法对正十二烷180组分1962步高温机理(温度大于1100 K)进行简化,获得40组分234步化学反应机理。在温度为1100–1650 K,压力为0.1–4 MPa条件下,采用简化机理及详细机理对不同当量比、压力下着火延迟时间进行模拟,模拟结果与实验数据吻合得较好。通过对不同压力及温度下火焰传播速度进行模拟,验证了简化机理能够正确地反映正十二烷的燃烧特性。利用C12H26/OH/H2O/CO2等重要组分随时间变化的数据,验证了简化机理能够准确描述燃烧过程反应物消耗、基团变化、生成物产生的过程,并表明该机理具有较高的模拟精度。利用该简化机理对本生灯进行数值分析,结果表明该机理能够准确地反映火焰区温度和组分浓度的变化。紧凑的正十二烷高温简化机理不仅能够正确体现其物理化学特性,而且能够用于三维数值模拟,具有较高的工程运用价值和应用前景。
固体氧化物燃料电池电化学阻抗谱差异化研究方法和分解
施王影, 贾川, 张永亮, 吕泽伟, 韩敏芳
2019, 35(5): 509-516  doi: 10.3866/PKU.WHXB201806071
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摘要:
电化学阻抗谱技术(EIS)在固体氧化物燃料电池(SOFC)中已获得广泛应用。在EIS分析过程中,研究者能够清楚地获得燃料电池内部因纯离子(电子)导电引起的欧姆电阻和因电化学过程、扩散作用引起的极化阻抗的大小,但是对于极化阻抗的构成缺乏进一步解析。本文选用传统的Ni-YSZ阳极支撑电池,通过改变测试温度、阳极运行气氛和阴极运行气氛,设计了一套完整的阻抗差异分析(ADIS)实验。并基于弛豫时间分布法(DRT)和阻抗差异分析法,系统地分析并解释了阻抗谱中各频率段对应阻抗的物理或(电)化学含义,将该类型电池阻抗谱以6个RQ并联电路予以拟合,为之后燃料电池性能稳定性的研究奠定基础。
原位透射电子显微镜观察电荷驱动的氧化物纳米颗粒水中自组装
赵喆, 卢岳, 张振华, 隋曼龄
2019, 35(5): 539-545  doi: 10.3866/PKU.WHXB201806012
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摘要:
以四氧化三钴Co3O4纳米棒为研究对象,我们利用液体环境透射电子显微镜,原位观察了四氧化三钴纳米棒在水中的自组装过程。研究发现在电子束辐照的水环境下,四氧化三钴纳米棒的晶面存在互补式自组装现象。随着纳米棒之间的距离越来越近,纳米棒之间的相对运动速率逐渐增加,纳米棒之间的相互作用力逐渐增加。通过进一步分析纳米棒的形貌发现,纳米棒的暴露晶面大多数为{100}、{110}以及{111}晶面,而Co3O4属于极性氧化物,这些晶面往往会带有一定的电荷。在液体环境下,正是由于这些易暴露面都带有不同大小的电荷,在晶面电荷的驱动下,电荷属性相反的四氧化三钴纳米棒会互相吸引,形貌结构上进行互补,实现快速驱动的纳米棒之间自组装。
ARTICLE
Perylenediimide: Phosphonium-Based Binary Blended Small-Molecule Cathode Interlayer for Efficient Fullerene-Free Polymer Solar Cells with Open Circuit Voltage to 1.0 V
Monika GUPTA, Dong YAN, Fugang SHEN, Jianzhong XU, Chuanlang ZHAN
2019, 35(5): 496-502  doi: 10.3866/PKU.WHXB201805101
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摘要:
The fabrication of high-efficiency organic solar cells requires a cathode interlayer (CIF) having multiple properties such as forming an ohmic contact with the active layer, high electron conductivity, low-density traps, and hole blocking. These roles can be more completely fulfilled by using a suitable binary blended CIF rather than a single molecule based CIF. In this article, we present the roles by using binary blended PDINO (amino N-oxide perylene diimide) and QPhPBr (tetraphenylphosphonium bromide) as the CIF to fabricate fullerene-free polymer solar cells (PSCs) with PBDB-T:IDTBR, a new donor: acceptor combination, as the active layer. The high-lying lowest unoccupied molecular orbital of the acceptor and the low-lying highest occupied molecular orbital (HOMO) of the polymer with small driving force (the donor-acceptor HOMO-HOMO energy offset, ∆HOMO) for the hole transfer, both result in a high open circuit voltage (Voc). Moreover, our strategy to insert a dual mixed solution of CIF over the blended active layer better facilitates the role, which significantly improves charge extraction and collection, leading to the high Voc, short-circuit current density (Jsc), and fill factor (FF) observed in comparison to a single CIF material. It was observed that the power conversion efficiency (PCE) increases to 8.27%, with a high Voc of 1.0 V, using a binary mixture of CBL. Such tremendous improvements in Voc using well known polymer donors have not been reported till date in binary solar cell systems. This idea demonstrates that the minimum energy loss because of the small ∆HOMO of the D-A combination and the use of a dual mixed layer of CBL together present the future prospects of non-fullerene photovoltaic devices for researchers.
Bandgap Modulation of Dithienonaphthalene-Based Small-Molecule Acceptors for Nonfullerene Organic Solar Cells
Meiqi ZHANG, Yunlong MA, Qingdong ZHENG
2019, 35(5): 503-508  doi: 10.3866/PKU.WHXB201805151
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摘要:
By using photovoltaic technology, ambient solar light can be directly converted to electricity. The photovoltaic technology has been regarded as one of the most important and promising strategies to resolve the worldwide energy and pollution problems. As one type of photovoltaic technology, polymer solar cells have attracted increasing interest due to their advantages of solution processing capability, low-cost, feasibility to be fabricated on flexible substrates etc. Not until a few years ago, the fullerene derivatives had been dominated the organic photovoltaic field as the most promising acceptor materials for polymer solar cells. However, fullerene-based polymer solar cells have a power conversion efficiency bottleneck due to the relatively fixed energy levels as well as the fixed bandgaps of fullerene derivatives. Therefore, researchers started to develop nonfullerene acceptors which can be used as alternatives to replace the traditional fullerene derivatives. Compared to the fullerene derivatives, nonfullerene acceptors offer several advantages such as stronger light absorption, tunable bandgaps and frontier molecular orbital energy levels. For nonfullerene acceptors, a ladder-type fused ring is usually used as the central core which is an essential building block to tailor the bandgaps and energy levels. Although many fused ring systems have been explored for efficient nonfullerene acceptors, ladder-type angular-shape dithienonaphthalene is seldom reported as the donor unit for nonfullerene acceptors. Furthermore, the impact of thiophene bridge on the optical and photovoltaic properties of the dithienonaphthalene-based nonfullerene acceptors has never been reported. In this context, we report on the design and synthesis of a dithienonaphthalene-based small-molecule acceptor which contains thiophene bridges in between the acceptor terminals and the fused-ring donor core. Compared to the dithienonaphthalene-based small-molecule without the thiophene bridges, the resulting acceptor (DTNIT) exhibits a reduced bandgap of 1.52 eV which makes it more suitable to be blended with the benchmark large bandgap copolymer, poly[(2, 6-(4, 8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1, 2-b: 4, 5-b']dithiophene))-alt-(5, 5-(1', 3'-di-2-thienyl-5', 7'-bis(2-ethylhexyl)benzo[1', 2'-c:4', 5'-c']dithiophene-4, 8-dione)] (PBDB-T). The reduced band-gap of the resulting nonfullerene acceptor can be attributed to its extended π-conjugation in comparison with the dithienonaphthalene-based acceptor without the thiophene bridges. Inverted polymer solar cells with a device configuration of indium tin oxide/ZnO/PBDB-T:DTNIT/MoO3/Ag were fabricated and characterized. Polymer solar cells based on PBDB-T:DTNIT showed an open circuit voltage of 0.91 V, an enhanced short circuit current of 14.42 mA∙cm−2, and a moderate PCE of 7.05% which is comparable to the PCE of 7.12% for the inverted device based on PBDB-T:PC71BM. Our results not only provide a method to synthesize efficient nonfullerene acceptors with reduced bandgaps, but also offer a bandgap modulation strategy for nonfullerene acceptors.
Effect of Ink Solvents on Low-Pt Loading Proton Exchange Membrane Fuel Cell Performance
Wenhui CHEN, Shengli CHEN
2019, 35(5): 517-522  doi: 10.3866/PKU.WHXB201806011
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摘要:
Owing to the scarcity of platinum, it is of high importance to develop electrodes with low platinum metal loading and to thereby improve the utilization of Pt for the commercialization of proton-exchange membrane fuel cells (PEMFCs). In comparison to conventional high-platinum electrodes, the thickness of the catalyst layer (CL) is thinner and the interatomic Pt spacing is larger for the low-Pt loading electrodes. The distribution of electrolyte ionomer and the electrode morphology, which are strongly influenced by the solvents used in the fabrication process, are therefore increasingly important factors for achieving high performance in the membrane electrode assembly (MEA). In this work, different solvents with various dielectric constants and evaporation rates were used to prepare the inks for low-Pt loading cathode (0.1 mg·cm-2) fabrication. First, the inks were fabricated by dispersing the catalyst and ionomer in different solvents which were then coated onto carbon paper to prepare the gas diffusion electrodes. The anode and cathode electrodes were then hot-pressed together with the Nafion membrane to produce the MEAs. The results showed a mixture of isopropanol-water (4:1) yielded the best-performing MEA during the single-cell tests compared to the other solvents tested. In order to elucidate the relationship between the performance of MEAs and the solvents, the structure and the surface morphology of the CL and the distribution of Nafion ionomer in the CL was characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). A comparison of the SEM and TEM images of representative samples indicated that the best performing electrode had a much improved homogeneity in the surface morphology as well as the dispersion of catalyst and ionomer. This was because of the moderate evaporation rate and better dispersion, caused by the increased hydrogen bonding and high dielectric constant, respectively. The results from dynamic light scattering (DLS) showed that the size of the catalyst and ionomer aggregates are influenced by the solvents. It is suggested that larger aggregates might help the formation of holes in the CL for gas diffusion and water removal, with the optimum size found to be around 400–800 nm. In conclusion, the MEA fabricated from the isopropanol-water solvent exhibited a significantly increased power density (1.79 W·cm-2), and the utilization of Pt was increased to approximately 0.047 mg·W-1, which is among the best-performing fuel cells reported to date.
Molybdenum Carbide Prepared by a Salt Sealing Approach as an Electrocatalyst for Enhanced Hydrogen Evolution Reaction
Zhou LIN, Linfan SHEN, Ximing QU, Junming ZHANG, Yanxia JIANG, Shigang SUN
2019, 35(5): 523-530  doi: 10.3866/PKU.WHXB201806191
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摘要:
Molybdenum carbide is regarded as an excellent substitute for Pt-based catalysts in the hydrogen evolution reaction (HER), owing to its low cost, superior catalytic performance, and long-term stability. In this work, salt-sealed molybdenum carbide was prepared using sodium molybdate and 2, 6-diaminopyridine as the reactive raw materials, followed by continuous salt sealing and calcination of the precursor under an inert atmosphere. The morphology, composition and structure of salt-sealed molybdenum carbide were determined by scanning electron microscopy, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results indicate that salt-sealed molybdenum carbide has irregular morphology and includes nanoparticles and nanorods. A comparison of the TEM images of Mo2C with salt sealing (Mo2C/SS) and Mo2C without salt sealing (Mo2C) indicates that Mo2C/SS exhibits a smaller particle size. This suggests that salt sealing can efficiently avoid particle aggregation. The Brunauer-Emmett- Teller (BET) specific surface area of the catalysts was obtained from nitrogen adsorption/desorption isotherms. The increase in BET surface area from 2.55 to 8.14 m2·g−1 after salt sealing provides evidence for the formation of pores in the product. The results of XRD, EDS and XPS analyses show that Mo2C/SS has an orthorhombic crystal structure with molybdenum oxides on the surface, which may originate from surface oxidation. Considering the results of XPS and the turnover frequency (TOF) calculation, we can conclude that the formation of pores via salt sealing contributes to the exposure of more active sites, while simultaneously enlarging the contact area with oxygen. Therefore, higher molybdenum oxide content is generated on the surface, resulting in a lower proportion of active centers (molybdenum carbides) on the catalyst surface. Furthermore, the pseudocapacitance generated by the faradaic reaction of molybdenum oxides is superimposed on the double-layer capacitance of Mo2C catalysts, which increases the double layer capacitance. Since the effect of pseudo-capacitance on Mo2C/SS is more significant, the TOF number declines after salt sealing. Compared with Mo2C, Mo2C/SS exhibits three features that promote HER mass activity: (1) the generation of large quantities of pores via salt sealing leads to an increase in the BET surface area and exposure of more active sites, which is beneficial for improving HER performance; (2) the porous structure and enlarged surface area pave the way for effective mass and charge transfer; (3) the decrease of the Tafel slope from 145 to 88 mV·dec−1. In summary, salt-sealed Mo2C exhibited enhanced HER activity with an overpotential of 175 mV to achieve a current density of 10 mA·cm−2. The Tafel slope for HER on salt-sealed Mo2C is 88 mV·dec−1. This can be considered as the proof of the Volmer-Heyrovsky mechanism with electrochemical desorption as the rate-determining step.
Reactivities of VO1–4+ Toward n-CmH2m+2 (m = 3, 5, 7) as Functions of Oxygen Content and Carbon Chain Length
Yue ZHAO, Jiatong CUI, Jichuang HU, Jiabi MA
2019, 35(5): 531-538  doi: 10.3866/PKU.WHXB201805231
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摘要:
Vanadium oxides are one of the most important heterogeneous catalysts that are widely used to oxidize hydrocarbon molecules into value-added chemicals. In order to reveal the mechanisms and the nature of active sites, numerous experimental and theoretical studies have been reported on the reactivities of gas-phase vanadium oxide clusters toward small molecules. However, there has been very limited research on the chemical reactivity changes associated with the oxygen contents of vanadium oxides and the carbon chain lengths of alkanes. In this work, the reactions of vanadium oxide ions VO1−4+ with alkanes (n-CmH2m+2, m = 3, 5, 7) were systematically investigated by time-of-flight mass spectrometry and the reactions of VO1−3+ with pentane were further studied by density functional theory calculations. Experimental results show that in the reactions of VO+, VO3+, and VO4+ with n-C5H12, in addition to the major adsorption processes, the activation of the C―H and C―C bonds of n-C5H12 was observed. The activation of both the bonds was observed experimentally during the reaction of VO2+ with n-C5H12 with large branching ratios. Among the vanadium oxide cations studied, VO2+ shows the strongest oxidizability and the generation of lighter alkanes and alkenes dominates the reactions; VO+ is more reactive than VO3+. VO4+ pocesses only one η2-O2 unit. Due to the weak bond between VO2+ and η2-O2, the η2-O2 unit is released in VO4+/n-C5H12 system leading to the formation of VO2+; thus VO4+ cations reflect some reactivity of VO2+. Although the oxidation states in the vanadium oxide clusters increase from +Ⅲ in VO+ to +Ⅴ in VO2+ and +Ⅳ in VO3+, the reactivity does not gradually increase. Moreover, the reactivity of the mononuclear vanadium oxide cations also does not exhibit a gradually increasing trend with the increase in oxygen content. Based on the observed reactivity trend, the adsorption channels gradually become weak as the carbon chain lengths increase; meanwhile, the dehydrogenation and C―C bond activation channels gradually become obvious and some oxygen transfer products appear. Therefore, much lighter fragments of alkanes/alkenes will be obtained if linear alkanes with more carbon atoms were reacted with VO1−4+. The theoretical results are generally consistent with those obtained from the experiments. The various reaction channels and versatile reactivity of the mononuclear vanadium oxide cations investigated in this study not only offer new insights into gas-phase reactions but also shed light on the processes occurring on the surfaces of the corresponding condensed-phase catalysts.
Single-Molecule Study on the Folding of OmpT in Tween-20 Micelles
Peixuan BU, Chenhui HE, Xinsheng ZHAO
2019, 35(5): 546-554  doi: 10.3866/PKU.WHXB201806072
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摘要:
The cell envelope of gram-negative bacteria consists of the outer membrane (OM), inner membrane (IM), and periplasm. The β-barrel outer membrane proteins (OMPs) embedded in the OM perform diverse and significant functions such as signaling, transporting, and proteolysis. The OMPs of gram-negative bacteria share similar folding pathways with that of mitochondria and chloroplasts. Therefore, the study of the OMP folding mechanism not only provides insights into antimicrobial drug design but also helps elucidate mitochondrial and chloroplast biogenesis. Most knowledge about OMP folding was obtained from ensemble experiments where OMPs were usually at micromolar concentrations and prone to aggregate, which is different from the physiological environment in the cells. Unlike ensemble techniques, single-molecule detection (SMD) can measure OMPs from nano- to picomolar concentrations and prevent aggregation. In this work, we investigated the folding of OmpT, one of the OMPs, in Tween-20 and n-dodecyl β-d-maltopyranoside (DDM) micelles by SMD. We prepared monodisperse OmpT and observed both unfolded and folded OmpT in Tween-20 and DDM micelles under different urea concentrations by single-molecule fluorescence resonance energy transfer (FRET). The folded OmpT in Tween-20 is structurally similar to the native OmpT folded in DDM but exhibits weaker resistance to urea. In contrast, OmpA barely folds and OmpC hardly folds in Tween-20 micelles. We confirmed that folded OmpT forms complexes with detergent micelles and estimated the number of bound Tween-20 and DDM molecules per OmpT by fluorescence correlation spectroscopy. We compared the enzymatic activity of OmpT folded in two detergents with a fluorescent peptide as substrate, and found that the folded form of OmpT in Tween-20 possesses weaker enzymatic activity than that in DDM. We also investigated the folding properties of OmpT, OmpA, and OmpC in the presence of the β-barrel assembly machine (BAM) complex. OmpT folds efficiently in liposome even without the BAM complex; OmpA only folds with the help of the BAM complex; and OmpC does not fold with or without the BAM complex. Based on the comparison of the folding of OmpT, OmpA, and OmpC in detergent micelles and in the presence of the BAM complex, we propose that OmpT has stronger folding tendency than OmpA and OmpC, which supports the idea that the exact role of the BAM complex is dependent on the distinct folding properties of individual OMPs. Since Tween-20 is a widely used reagent to block nonspecific adsorption in SMD experiments, our results also remind people to exercise caution to prevent possible wrong interpretations caused by the interaction between proteins and Tween-20.

编委会

发布时间:


《物理化学学报》第4届编委会

(按拼音排序)

名誉主编

唐有祺

北京大学

顾问编委

包信和

中国科学院大连化学物理研究所

段雪

北京化工大学

付贤智

福州大学

侯建国

中国科学技术大学

黄维

南京工业大学

LIEBER Charles M.

Harvard University

田中群

厦门大学

万立骏

中国科学院化学研究所

吴云东

北京大学

谢晓亮

Harvard University, 北京大学

杨伟涛

 Duke University

姚建年

中国科学院化学研究所

赵新生

北京大学

主编

刘忠范

北京大学

副主编

韩布兴

中国科学院化学研究所

刘鸣华

国家纳米科学中心

申文杰

中国科学院大连化学物理研究所

吴凯

北京大学

杨金龙

中国科学技术大学

庄林

武汉大学

迟力峰

苏州大学

编委

曹勇

复旦大学

陈经广

University of Delaware

陈军

南开大学

崔屹

Stanford University

邓风

中国科学院武汉物理与数学研究所

邓友全

中国科学院兰州化学物理研究所

樊卫斌

中国科学院山西煤炭化学研究所

房喻

陕西师范大学

付红兵

中国科学院化学研究所

傅强

中国科学院大连化学物理研究所

高毅勤

北京大学

郭林

北京航空航天大学

郝京诚

山东大学

侯文华

南京大学

金荣超

Carnegie Mellon University

来鲁华

北京大学

李朝军

McGill University

李隽

清华大学

李象远

四川大学

梁万珍

厦门大学

刘海超

北京大学

刘洪来

华东理工大学

刘述斌

University of North Carolina

刘义

武汉大学

刘志敏

中国科学院化学研究所

罗小民

中国科学院上海药物研究所

马晶

南京大学

孟庆波

中国科学院物理研究所

邵翔

中国科学技术大学

孙俊奇

吉林大学

谭蔚泓

湖南大学

唐智勇

国家纳米科学中心

王键吉

河南师范大学

王鹏

中国科学院长春应用化学研究所

王心晨

福州大学

王永锋

北京大学

魏子栋

重庆大学

翁羽翔

中国科学院物理研究所

吴鹏

华东师范大学

夏永姚

复旦大学

许国勤

National University of Singapore

杨俊林

国家自然科学基金委员会

余家国

武汉理工大学

尉志武

清华大学

占肖卫

北京大学

张东辉

中国科学院大连化学物理研究所

张浩力

兰州大学

张锦

北京大学

章俊良

上海交通大学

周永贵

中国科学院大连化学物理研究所

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发布时间: 2018-05-02


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发布日期:2009-06-24 浏览: