应用扫描电化学显微镜研究电子在室温离子液体与1,2-二氯乙烷混合溶液/水相界面上的转移反应

应用扫描电化学显微镜研究了室温离子液体(Omim·Tf2N)与1,2-二氯乙烷(DCE)混合溶液/水界面上的电子转移反应. 在保持共同离子(Tf2N-)的浓度比恒定及异相电子转移反应由界面电势差所决定的条件下, 研究了离子液体和DCE混合溶液中二茂铁(Fc)与水相中亚铁氰化钾[K4Fe(CN)6]之间异相电子转移反应. 探讨了混合溶液中离子液体的体积分数(xRTIL)的变化对混合溶液/水界面上电子转移反应的影响. 结果表明, 随着xRTIL的减小(从1减小到0.1), Fc在混合溶液中的扩散系数单调递增(从2.730×10-7 cm2·s-1增加到9.131×10-6 cm2·s-1); 而异相电子转移反应速率常数(k)则先逐渐减小(从8.0 mol-1·cm·s-1减小到0.32 mol-1·cm·s-1), 之后又略有增大(从0.32 mol-1·cm·s-1增大到0.48 mol-1·cm·s-1). 对这种现象可能的原因进行了较详细探讨.     

偶氮苯光致异构化对紫精-曙洪络合的调控

报导了α，ω－偶氮苯，紫精双发色团化合物的合成与性质研究，结果表明偶氮苯的光致顺反异构化以可调控与之相连的紫精与曙红络合行为，其作用程度的强弱与连接两者的亚甲基链的长度有关，借助ＨＮＭＲ通过对构象进行分析解释了上述的研究结果。     

Cathodic synthesis of esters of 1,1,2,2-cycloalkanetetracarboxylic acids derived from 1,1,2,2-ethane- or ethylenecarboxylate esters

The cathodic electrolysis of esters of 1,1,2,2-ethane- or ethylenetetracarboxylic acids in the presence of dihaloalkanes leads to esters of 1,1,2,2-cycloalkanetetracarboxylic acids.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 217–220, January, 1992.     

Copper‐Bismuth Bimetallic Microspheres for Selective Electrocatalytic Reduction of CO2 to Formate

Electrocatalytic carbon dioxide reduction holds great promise for reducing the atmospheric CO₂ level and alleviating the energy crisis. High‐performance electrocatalysts are often required in order to lower the high overpotential and expedite the sluggish reaction kinetics of CO₂ electroreduction. Copper is a promising candidate metal. However, it usually suffers from the issues of poor stability and low product selectivity. In this work, bimetallic Cu‐Bi is obtained by reducing the microspherical copper bismuthate (CuBi₂O₄) for selectively catalyzing the CO₂ reduction to formate (HCOO^–). The bimetallic Cu‐Bi electrocatalyst exhibits high activity and selectivity with the Faradic efficiency over 90% in a wide potential window. A maximum Faradaic efficiency of ~95% is obtained at –0.93 V versus reversible hydrogen electrode. Furthermore, the catalyst shows high stability over 6 h with Faradaic efficiency of ~95%. This study provides an important clue in designing new functional materials for CO₂ electroreduction with high activity and selectivity.     

锂离子电池锡氧化物基负极材料的湿化学合成与电化学性质

采用新兴的湿化学方法合成了锡氧化物基粉末材料。用X-射线衍射、扫描电镜和电化学方法对材料的微观结构、形貌和电化学性能进行了详细的研究。结果表明，经400 ℃热处理4 h的锡氧化物基材料的颗粒大小均匀，平均粒径约为200 nm。这种材料的可逆充电容量超过570 mAh·g^-1，30次循环后平均每次循环的容量衰减只有0.15%。良好的电化学性能表明锡氧化物基材料有望作为新一代锂离子电池的负极材料。     

磺胺甲恶唑在二硫化钼纳米片修饰电极上的电化学行为

采用了研磨后超声和离心分离方法制备了二硫化钼纳米片,通过原子力显微镜(AFM)和扫描电子显微镜(SEM)对不同离心速度分离的二硫化钼纳米片进行了表征。使用循环伏安法(CV)和差分脉冲伏安法(DPV)在磺胺甲恶唑溶液中对二硫化钼纳米片修饰的玻碳电极进行了电化学行为研究。结果显示,磺胺甲恶唑在二硫化钼修饰电极的循环伏安图上有一对氧化还原峰。其峰电流值与扫描速度的平方根成正比,是扩散控制过程。DPV扫描结果显示,磺胺甲恶唑的峰电流与其浓度之间存在着明显的线性关系。研磨超声方法制备出的二硫化钼纳米片层材料在电极上能够加速电子的转移和传输,从而有效提高峰电流值,为进一步研制准确测定磺胺甲恶唑电化学传感器提供了一种可选择的材料和电化学分析方法。     

Photoinduced processes within compact dyads based on triphenylpyridinium-functionalized bipyridyl complexes of ruthenium(II)

As an alternative to conventional charge-separation functional molecular models based on long-range ET within redox cascades, a "compact approach" has been examined. To this end, spacer elements usually inserted between main redox-active units within polyad systems have been removed, allowing extended rigidity but at the expense of enhanced intercomponent electronic communication. The molecular assemblies investigated here are of the P-(theta (1))-A type, where the theta (1) twist angle is related to the degree of conjugation between the photosensitizer (P, of {Ru(bpy)(3)}(2+) type) and the electron-acceptor (A). 4-N- and 4-N-,4'-N-(2,4,6-triphenylpyridinio)-2,2'-bipyridine ligands (A(1)-bpy and A(2)-bpy, respectively) have been synthesized to give complexes with Ru(II), 1-bpy and 2-bpy, respectively. Combined solid-state analysis (X-ray crystallography), solution studies ((1)H NMR, cyclic voltammetry) and computational structural optimization allowed verifying that theta (1) angle approaches 90 degrees within 1-bpy and 2-bpy in solution. Also, anticipated existence of strong intercomponent electronic coupling has been confirmed by investigating electronic absorption properties and electrochemical behavior of the compounds. The capability of 1-bpy and 2-bpy to undergo PET process was evaluated by carrying out their photophysical study (steady state emission and time-resolved spectroscopy at both 293 and 77 K). The conformational dependence of photoinduced processes within P-(theta (1))-A systems has been established by comparing the photophysical properties of 1-bpy (and 2-bpy) with those of an affiliated species reported in the literature, 1-phen. A complementary theoretical analysis (DFT) of the change of spin density distribution within model [1-bpy(theta (1))](-) mono-reduced species as a function of theta (1) has been undertaken and the possibility of conformationally switching emission properties of P was derived.     

类球形正交LiMnO2的制备、微结构和电化学性能

以共沉淀法得到的类球形MnCO₃为前驱物，制备了类球形正交LiMnO₂(So-LiMnO₂)，采用XRD、SEM和N₂吸附技术对样品进行表征；与非球形正交LiMnO₂(No-LiMnO₂)进行了对比研究。结果表明：o-LiMnO₂的堆垛层错度、结晶状况、颗粒形貌和大小与前驱物的微结构密切相关；在80次电化学循环测试过程中，So-LiMnO₂经15次循环可达最大的放电容量152 mAh·g^-1，其容量衰减平均每次循环0.58 mAh·g^-1；而No-LiMnO₂要经过38次循环才能达到最大放电容量128 mAh·g^-1，容量衰减平均每次循环高达1.24 mAh·g^-1。TEM和EDS分析证明：由一次粒子团聚的类球形So-LiMnO₂能有效地抑制电解液对材料的腐蚀、减少Mn的溶解，从而提高了电化学循环能力。     

A Procedure for Transforming Impedance Spectra for the Determination of Mechanism of Electrochemical Reactions

Transformation of impedance spectra into relaxation time spectra (RTS) is used for determining contributions of individual processes of the oxygen electroreduction reaction (OER) to the polarization resistance of the electrochemical cell. The transformation technique involves the solution of the convolution equation found with the aid of a modified Van Cittert iteration algorithm checked on model impedance spectra. The technique, when used to analyze impedance spectra of electrochemical cells air|Pt|YSZ|YSZ + Pt|air, shows that the conversion of a globular structure of the YSZ + Pt cermet layer to a columnar one is accompanied by a change of peak amplitudes in RTS. The revealed RTS dynamics when heated to 750°C is compared with peculiarities of individual processes in OER.     

Monolayer Rectifiers

Molecular-scale electronics has now been enriched by the discovery that molecules, studied singly by scanning tunneling spectroscopy, or a large array of those molecules, studied in parallel as a Langmuir-Blodgett monolayer between metal electrodes, exhibit rectification, i.e., an asymmetric current as a function of applied voltage.This asymmetry can come, first, from work function differences between two dissimilar metals or the metal-molecule interfaces (Schottky barriers), second from an asymmetric placement of the chromophore between the two metal electrodes, and third, from an asymmetry of the molecular orbitals of the molecule.This third, electronic origin of rectification, first proposed by Aviram and Ratner in 1974, and confirmed in the work reported here, gives us hope that, not too many years from now, molecules can form the basis of ultra-small yet ultra-fast electronic devices and integrated circuits.