Selective hydrogenation of dimethyl maleate to tetrahydrofuran over Cu/SiO2 catalyst: Effect of Cu+ on the catalytic performance

Cu/SiO_2 catalysts prepared by different methods have been investigated focusing on the influence of Cu~+on the catalytic performance.The composition,structure and copper valence state were characterized by means of BET,XRD,XPS,FTIR,N_2O-titration.It was found that the Cu/SiO_2 prepared by ammoniaevaporation(AE) method had much higher TOF value than that prepared by wetness-impregnation(WI)with the same THF selectivity.The higher TOF value was attributed to the coexistence of Cu~+ and Cu~0species in the activated AE-Cu/SiO_2.while only Cu° species existing in the activated Wl-Cu/SiO_2.Researches suggest that Cu~+ can adsorb and polarize the C=0 bond of DMM.It is concluded that Cu°could be the main active site and the synergistic effect between Cu~0 and Cu~+ could contribute to hydrogenation of DMM to THF.     

铂铋金属间化合物催化剂的氧还原与抗甲醇氧化性能

采用氩弧熔炼后热处理方法制备了PtBi金属间化合物材料.采用循环伏安法和旋转圆盘电极进行电化学性能测试.通过在0.5 mol•L^－1 H₂SO₄＋0.25 mol•L^－1 CH₃OH溶液中对氧还原的起始电位和电流密度大小比较发现,与光滑铂电极相比,PtBi金属间化合物具有良好的氧还原催化性能和抗甲醇中毒性能.从结构方面分析了PtBi具有抗甲醇中毒性能的原因,认为是PtBi中Pt-Pt的间距大，不利于甲醇的吸附解离. X射线光电子能谱(XPS)结果表明,PtBi材料中Pt的d电子空穴增加,可能是导致PtBi电极表面氧还原电流增大的原因.     

Highly Uniform Alkali Doped Cobalt Oxide Derived from Anionic Metal-Organic Framework: Improving Activity and Water Tolerance for CO Oxidation

A sequence of alkali metal cation-exchanged Co metal-organic frameworks(Co-MOFs), therein after denoted as M@Co-MOF, M=Na⁺, K⁺, Rb⁺, and Cs⁺, was prepared and used as the precursors to obtain the corresponding alkali doped cobalt oxide(defined as M/Co₃O₄, M=Na⁺, K⁺, Rb⁺, and Cs⁺) through calcination under air atmosphere. The cobalt oxide modified by uniform alkali metals exhibited a significant promotion of catalytic activity for CO oxidation. The activity of M/Co₃O₄ decreased in the order of Cs⁺ > Na⁺ > K⁺ > Rb⁺. Experimental and theoretical results revealed that the anionic skeleton of Co-MOF could facilely adsorb alkali metal cations and play a crucial role in the formation of highly uniform alkali doped cobalt oxide. The further characterizations, such as temperature-programmed reduction of H₂(H₂-TPR), oxygen temperature-programmed desorption(O₂-TPD), X-ray photoelectron spectroscopy(XPS), and in situ diffuse reflectance infrared Fourier transform(DRIFT) spectra demonstrated that the enhanced catalytic activity is originated from the interfacial electron transfer as well as weakened the Co-O bond strength, which promoted oxygen desorption from Co₃O₄ and formation of cobalt species with the lower valence state. The Cs/Co₃O₄ catalyst was maintained for 60 h without deactivation and still showed a high activity in the presence of water.     

胶体离子超级电容器的比容量评价

胶体离子超级电容器作为一种新型的超级电容器,其同时具有能量密度和功率密度高的独特优势。 目前已经发展了包括多种过渡金属阳离子和稀土阳离子,例如Mn²⁺、Fe²⁺、Co²⁺、Ni²⁺、Cu²⁺、Sn²⁺、Sn⁴⁺、La³⁺、Ce³⁺、Er³⁺和Yb³⁺的胶体离子超级电容器体系。 在电化学反应中,识别出电活性物质的存在形式对研究电极反应机理和提高比容量具有重要价值。 本文主要通过对电活性物质比容量的探讨,理解这种新型胶体离子超级电容器的电化学储能机理。 评述了胶体离子超级电容器的比容量核算方式,提出了以阳离子为标准核算比容量的原因,并与传统超级电容器的核算方式进行了比较,表明胶体离子超级电容器在提高能量密度方面具有潜在优势,有望突破现有电化学储能设备的技术瓶颈,实现下一代高能量储能器件的开发。     

模拟胃肠道消化液中小球藻类金属硫蛋白对镉离子的结合作用研究

利用锌诱导小球藻,通过提取分离和纯化,获得锌结合类金属硫蛋白(MT-like蛋白)。通过透析过程,研究模拟胃、肠道消化液中MT-like蛋白对Cd²⁺的结合作用。结果表明,在模拟胃液中MT-like蛋白处于脱金属状态,与Cd²⁺的结合能力弱。而在肠消化液中,MT-like蛋白能与Cd²⁺结合,20 mg·L^-1 MT-like蛋白与100μg·L^-1 Cd²⁺的结合率可达46.0%。研究发现,在模拟胃、肠液中胃蛋白酶和胰蛋白酶都会降低MT-like蛋白对Cd^2+的结合能力。研究结果对进一步开发MT-like蛋白作为Cd²⁺的生物解毒剂具有重要意义。     

Mo-Fe-S三元包合物氧化还原特性的研究

本文结合电化学测量和量子化学计算对Mo-Fe-S三元包合物的氧化还原特性进行了研究。用铂电极测得的该包合物在0.1MKClO₄-DMF溶液中的循环伏安图显现出两对氧化-还原峰,由此得到的电化学参数与EHMO计算结果都表明,电位较正的一对峰相应于Fe(Ⅲ)/Fe(Ⅱ)的氧化还原,反应不可逆。电位较负的一对峰相应于Mo(Ⅴ)/Mo(Ⅳ)的氧化还原反应半可逆。     

Electrochemical sensor for Cd2+ and Pb2+ detection based on nano-porous pseudo carbon paste electrode

An electrochemical sensor based on self-made nano-porous pseudo carbon paste electrode (nano-PPCPE) has been successfully developed, and used to detect Cd²⁺ and Pb²⁺. The results showed that the electrodes can quantitatively detect trace Cd²⁺ and Pb²⁺, and with satisfied limit of detection, which has great significance in electrochemical analysis and detection.     

明胶保护的铂在联吡啶钌体系中光助催化分解水产氢的研究

以联吡啶钌络合物Ru(bipy)₃²⁺为光敏剂,甲基紫精MV²⁺为电子交换的中继物,EDTA为电子给体,氯铂酸钾为催化剂,探讨了该体系在可见光照射下,光还原水产氢的结果。提出了用明胶作为铂催化剂的稳定剂,可以提高放氢的速度和保护催化剂不受破坏。讨论了该体系光助催化分解水产氢的可能的机理。     

电解液对水系可充电池MnO2正极电化学性能的影响

研究了水系电解液中Li⁺、Zn²⁺和Mn²⁺阳离子对具有不同晶型结构和形貌的MnO₂正极电化学性能的影响,探讨其储能机理。结果表明,在不含Mn(II)离子的水溶液中,MnO₂电极所表现的电化学性能趋同,容量低,衰减快。含有Zn²⁺离子的水溶液中,MnO₂电极因二价锌离子的嵌入-脱出,容量明显提升,但衰减严重。当溶液中同时含有Zn²⁺、Mn²⁺离子时,基于Mn²⁺和Zn²⁺离子之间的协同作用和Mn²⁺离子氧化/还原反应过程的作用,有效抑制MnO₂颗粒的聚集和结构塌陷,削弱碱式硫酸锌杂质不利的影响,保持了锌离子在MnO₂电极中嵌入-脱出的高容量特性(200 mAh·g^-1,电流密度：100 mA·g^-1),及良好的循环稳定性。     

改性层状双氢氧化物对铜离子(Ⅱ)和双酚A的协同吸附

采用离子交换法制备了十二烷基苯磺酸根(DBS^-)和柠檬酸根(Cit^3-)复合改性层状双氢氧化物(LDHs),简写为DBS-Cit-LDHs。 利用粉末X射线衍射分析、红外光谱分析、比表面积测定以及元素分析等技术手段对样品进行了表征。 结果表明,DBS^-和Cit^3-已柱撑进入LDHs层间。 研究了DBS-Cit-LDHs对水中重金属离子Cu²⁺和有机污染物双酚A(BPA)的协同吸附性能。 吸附实验结果表明,DBS-Cit-LDHs能同时高效去除Cu²⁺和BPA;对Cu²⁺的强吸附能力缘于DBS-Cit-LDHs层间Cit^3-与Cu²⁺形成了稳定配合物;对BPA的强吸附能力缘于分配作用,且吸附能力与样品比表面积无关。 DBS-Cit-LDHs对Cu²⁺的吸附动力学和热力学分别符合准二级动力学方程和Freundlich等温式;对BPA的吸附分别符合准一级动力学方程和Linear等温式。 二者吸附过程的ΔG^o和ΔH^o均为负值,表明吸附为自发放热过程。     

电活性铁氰化镍膜电极对稀土钇的电控离子分离

通过电沉积方法分别在镀铂石英晶片和铂基底上制备了电活性铁氰化镍膜,并考察了膜电极在含钇离子溶液中的电控离子交换性能. 在0.1 mol·L^-1的硝酸钇溶液中,使用循环伏安法及石英晶体微天平技术测试考察了铁氰化镍膜对钇离子的置入释放性能及对应的质量变化,同时比较了铁氰化镍膜电极在Y(NO₃)₃和Sr(NO₃)₂溶液中的电化学性能. 在0.1 mol·L^-1 [Y(NO₃)₃ + Sr(NO₃)₂]混合溶液中,通过循环伏安法分析了薄膜对Y³⁺/Sr²⁺离子的选择性. 用扫描电子显微镜观察了铁氰化镍膜的表面形貌,并通过X射线光电子能谱仪测定了膜在氧化和还原状态下的元素组成. 结果表明,铁氰化镍膜在含Y³⁺溶液中具有良好的离子交换行为,其中氧化过程薄膜质量减少,对应着钇离子的释放;还原过程薄膜质量增加,对应钇离子的置入;在0.0 V或0.9 V调控膜电极的氧化还原状态实现对钇离子的有效分离.     

On-line electrochemical detection of carbohydrates coupled with the periodate oxidation

A new concept of an amplified electrochemical detection of carbohydrates is proposed, where carbohydrates are oxidized by periodate ion (IO₄⁻) in acidic solutions to yield iodate ion (IO₃⁻) which would be electrochemically reduced into iodide ion (I⁻) under suitable conditions. This scenario allows highly sensitive detection of carbohydrates, for example, as 30 electrons per aldohexose molecule. Our cyclic voltammetric study revealed that IO₃⁻ is reduced at much lower overpotentials than IO₄⁻ at gold, platinum and carbon-based electrodes despite the fact that the standard redox potential of the IO₃⁻/I⁻ couple is more negative than that of the IO₄⁻/I⁻ couple. In the electrochemical reduction of IO₃⁻, I⁻ is considered to function as a mediator. Stable flow-through detection of IO₃⁻ in the presence of IO₄⁻ was realized at glassy carbon electrodes. This method was coupled with the IO₄⁻ oxidation of carbohydrates and the experimental conditions were partially optimized on a flow injection system. The IO₄⁻ oxidation-coupled electrochemical detection of carbohydrates was applied to ligand-exchange high-performance liquid chromatography in a post-column mode. Sub-nanomole order of carbohydrates were successfully detected on this system.     

La~(3+)掺杂NiCo层状双金属氢氧化物纳米片的合成及其电化学性能

稀土离子La~(3+)掺杂的NiCo层状双金属氢氧化物纳米片具有高的超级电容器性能,比容量达到1115 F/g(1A/g)、倍率性能为517 F/g(30 A/g)。研究表明,La~(3+)离子掺杂不改变NiCo层状双金属氢氧化物晶体结构,但会显著影响其电子和离子传导特性,从而改变其电化学性能。根据离子电负性标度,La~(3+)(1.327)和Co~(2+)(1.377)离子的电负性值最接近,掺杂La~(3+)会优先取代Co~(2+)离子位置。由于La~(3+)离子的尺寸作用(106 pm),使得最优掺杂比例较小仅为0.26%,电化学结果表明较少的La~(3+)掺杂比例依然会显著调节NiCo层状双金属氢氧化物的电子/离子输运性质。     

Photophysical, electrochemical and electrochromic properties of copper-bis(4,4′-dimethyl-6,6′-diphenyl-2,2′-bipyridine) complexes

The synthesis, solution and solid state structural characterization, photophysical and electrochemical properties of two redox forms of an electrochromic copper-bis(4,4′-dimethyl-6,6′-diphenyl-2,2′-bipyridine) complex, [Cu(3)₂]ⁿ (n=+1, +2), are presented. Both complexes were characterized in the solid state by X-ray diffraction methods on single-crystals showing that both forms exist in a pseudo-tetrahedral coordination, and a comparison with other structures was made. Like most copper(I) complexes, the red [Cu(3)₂]⁺ complex shows a rather weak emission (Φ_em=2.7×10⁻⁴, dichloromethane). The lifetime of the emitting MLCT state is 34±1 ns, as observed with time resolved emission, and transient absorption (in deoxygenated dichloromethane). Typical emission and transient absorption spectra are presented. The transient absorption spectra indicate that the MLCT state absorbs stronger than the ground state, which is relatively uncommon for metal bipyridine complexes, i.e. no ground state bleaching is observed. The green [(3)₂Cu]²⁺ complex does not show any observable emission or transient absorption, which is a common feature for Cu(II) complexes of this type. The electronic absorption spectra of the chemically and electrochemically produced copper(I/II) complexes are identical. The repeated electrochemical conversion of the Cu(I) center into Cu(II) and vice versa does not cause any decomposition. This is consistent with a fully reversible Cu(I)/Cu(II) redox couple in the corresponding cyclic voltammogram, (E_1/2 (Cu(I)/Cu(II))=+0.68 V vs. SCE=+0.23 V vs. Fc/Fc⁺). These observations indicate that no large structural reorganization occurs upon electrochemical timescales (sub second), and that the different ways of generating the complexes does not effect their final structure, apart from the small differences observed in the X-ray structures of both forms. These characteristics make these complexes rather well suited for their incorporation into an electrochromic display configuration.     

含磷酰杂菲侧基的苯乙烯衍生物聚集诱导发光特性及其在过渡金属离子检测中的应用

以2-(6-氧化-6-氢-二苯基(c,e)<1,2>氧杂磷酰基)-1,4-二羟基苯(ODOPB) 为中心结构单元, 通过两步酯化反应, 在两侧分别引入4-戊氧基苯甲酰基和4-乙烯基苯甲酰基, 得到苯乙烯衍生物(MED).由于磷酰杂菲基团的大π共轭结构和极性共同作用, 使得形成聚集体后分子内转动受到限制, 降低了非辐射去活效率, 使 MED在达到一定聚集程度时, 荧光强度成倍增加, 呈现出聚集诱导发光增强(AIEE) 特性. 同时, Pt²⁺, Ru³⁺, Fe³⁺的加入对MED有显著的猝灭效果; 而Fe²⁺只是在形成聚集体过程中才有猝灭效果.     

Nafion/硫堇/铂纳米线复合电极的葡萄糖电催化活性

利用吸附在玻碳基底Nafion膜的负电性磺酸基与正电荷硫堇（Thi）相互作用,将电子媒介体固定电极表面,通过铂纳米线（PtNW）与硫堇间的键合作用及铂纳米线强吸附效应把葡萄糖氧化酶（GOD）固定于玻碳基底上,制得高灵敏电流型葡萄糖生物传感电极. 通过循环伏安法考察了电极的电化学特性,研究了该铂纳米线生物传感电极的葡萄糖电催化性能. 结果表明,该传感电极对葡萄糖有良好的电催化活性,线性响应范围1.0 × 10^-5 ~ 6.0 × 10^-3 mol·L^-1,检测限3.0 × 10^-6 mol·L^-1. 该传感电极制备简单、灵敏度高、重现性好.     

玻璃基片上纳米碳管电极的集成

利用微波等离子体化学气相沉积法在玻璃孔穴中定位生长纳米碳管电极, 分析了负偏压对纳米碳管电极生长的影响. 该电极对铜离子的电化学检测性能分析结果表明, 所制备的纳米碳管电极具有良好的电化学检测性能, 位于－0.0100 V附近的铜离子的还原峰峰形良好, 其电流在铜离子浓度为0.01~0.30 mmol•L^-1时, 与Cu²⁺浓度呈良好的线性关系, 相关系数为0.9975, 且具有较好的长期稳定性和重现性.     

PANI-SnP复合膜电极在镍镉废水中电控离子交换性能

采用滴涂法在铂基底制备了电活性聚苯胺-磷酸锡(PANI-SnP)复合膜电极,考察了该电极在Ni²⁺、Cd²⁺溶液的电控离子交换性能. 用傅立叶变换红外光谱和扫描电镜分析观察复合膜的组成及表面形貌;在0.1 mol·L^-1 Ni(NO₃)₂、Cd(NO₃)₂溶液,通过循环伏安法比较了PANI膜、SnP膜及PANI-SnP复合膜电极的电化学性能,并结合电化学石英晶体微天平技术重点考察了PANI-SnP复合膜的离子交换机制;同时,通过循环伏安法调控复合膜电极的氧化还原电位,结合X射线能谱和X射线光电子能谱分别测定了其氧化和还原状态的元素组成. 结果表明,PANI-SnP复合膜电极在Ni²⁺、Cd²⁺溶液均有良好的氧化还原电活性和可逆离子交换性能,其Cd²⁺离子选择性优于Ni²⁺离子,通过电控离子交换可使Cd²⁺离子从镍镉废水高效分离.     

基于电化学方法测定饮用水源水中的痕量铜离子

本文建立了一种饮用水源水中痕量溶解态铜离子（Cu²⁺）的定性和定量电化学检测方法. 该方法首先通过电化学循环伏安法于玻碳电极表面制备粒径约为70 nm的金纳米粒子（Au NPs）,然后采用方波阳极溶出伏安法进行待测水样中Cu²⁺的定性定量分析. 研究结果表明,对于标准溶液,方法的检出限为1.3μg·L^-1,线性范围在2 ~ 50μg·L^-1之间,常见重金属离子对其定性定量分析几无影响. 在此基础上,将该方法应用于福建省重要的饮用水源水--闽江中游水样中Cu²⁺的含量分析,所得测试结果与国家标准方法（石墨炉原子吸收光谱法）无显著性差异,标准偏差在20%以内. 本方法具有电极制备简单、测定成本低以及分析快速等优点,进一步优化电极制备方法以提高方法的重现性和定量准确度,将可望用于现场测定各种饮用水源水中的痕量溶解态Cu²⁺.     

Structure and stability of (CuNO) isomers

Quantum-mechanical calculations have been performed on various isomers of the (CuNO)⁺ system. A ²Π ground state is found for the linear CuNO⁺ and CuON⁺ isomers and a ²A′ state for the bent CuNO⁺ and CuON⁺ isomers. Energy calculations indicate that the linear CuNO⁺ structure is the most stable, the bent CuNO⁺ and CuON⁺ and the linear CuON⁺ structures are at 0.86 eV, 0.99 eV and 1.04 eV above this respectively. In the CuNO⁺ → CuON⁺ interconversion between the linear isomers, three transition states are involved, whereas the bent CuNO⁺ isomer is found to be an intermediate species. The isomerization barriers, dissociation energies, equilibrium geometries and vibration frequencies are given for all isomers in their ground and first excited states.