New Type of an Adsorption Layer of Organic Molecules with a Cage Structure Condensed at the Electrode/Solution Interface: The Adsorption of Cubane Derivatives on a Mercury Electrode

A synthesis and a study by method of measuring the differential capacitance on a stationary mercury drop of the adsorption of a number of cubane derivatives in a surface-inactive electrolyte are performed. It is established that the compounds studied exhibit a high surface activity. For bromine derivatives of cubane (4-bromomethoxycarbonylcubane, 4-bromohydroxymethylcubane) the formation of two-dimensional adsorption layers is discovered. Values of adsorption parameters for these compounds are evaluated with use made of the Frumkin isotherm.     

Silver Cation Reduction on a Mercury Electrode: Effect of Two-Dimensional Condensed Layer of 1-AdOH during Individual Adsorption and Coadsorption with Tetraalkyl Cations

Effect of a condensed layer (CL) of 1-adamantanol (1-AdOH) during individual adsorption and coadsorption with tetraalkyl cations on the kinetics of the electroreduction (ER) of cation Ag⁺ at a mercury electrode is studied with the aim of revealing the link between the rate of electrode processes and the structure of two-dimensional CL. It is shown that ER of Ag⁺ occurs by means of penetration of the depolarizer particles through the adsorption layer. Polarization curves are calculated under the assumption that the potential barrier for ER of Ag⁺ in the presence of CL of 1-AdOH is defined by the work for overcoming two-dimensional pressure in the layer. Satisfactory agreement between experimental and calculated dependences in the region of ascending branches of polarization curves is demonstrated. It is established that the degree of the inhibiting action of mixed adsorption layers (as compared with individual CL of 1-AdOH) on ER of Ag⁺ depends on the 1-AdOH activity in solution and the nature of the organic cation. It is assumed that the latter effect is caused by the surface activity of cations studied.     

氢气在贮氢合金电极上析出反应机理的研究

贮氢合金电极上氢气的析出反应分为水分子的放电和吸附氢原子复合脱附两个步骤，即反应按Ｖｏｌｍｅｒ－Ｔａｆｅｌ机理进行，反应的超电势η可以区分为η１和η２两个组成部分，反映了Ｖｏｌｍｅｒ和Ｔａｆｅｌ反应的极化特征。析氢反应的速度由二者混合控制，在高超电势区，主要则由Ｖｏｌｍｅｒ反应所控制。     

Temperature Effect on Hydrogen Evolution Reaction at Au Electrode

The temperature dependence of hydrogen evolution reaction (HER) at a quasi-single crys-talline gold electrode in both 0.1 mol/L HClO₄ and 0.1 mol/L KOH solutions was investigated by cyclic voltammetry. HER current displays a clear increase with reaction overpotential (η) and temperature from 278～333 K. In 0.1 mol/L HClO₄ the Tafel slopes are found to increases slightly with temperature from 118 mV/dec to 146 mV/dec, while in 0.1 mol/L KOH it is ca. 153±15 mV/dec without clear temperature-dependent trend. The apparent activation energy (Ea) for HER at equilibrium potential is ca. 48 and 34 kJ/mol in 0.1 mol/L HClO₄ and 0.1 mol/L KOH, respectively. In acid solution, Ea decreases with increase in η, from Ea=37 kJ/mol (η=0.2 V) to 30 kJ/mol (η=0.35 V). In contrast, in 0.1 mol/L KOH, Ea does not show obvious change with η. The pre-exponential factor (A) in 0.1 mol/L HClO₄ is ca. 1 order higher than that in 0.1 mol/L KOH. Toward more negative potential, in 0.1 mol/L HClO₄ A changes little with potential, while in 0.1 mol/L KOH it displays a monotonic increase with η. The change trends of the potential-dependent kinetic parameters for HER at Au electrode in 0.1 mol/L HClO₄ and that in 0.1 mol/L KOH are discussed.     

牛红细胞铜锌超氧化物歧化酶（BESOD）在汞电极表面吸附行为的研究

牛红细胞铜锌超氧化物歧化酶（ＢＥＳＯＤ）在汞电极表面吸附行为的研究钱雯，孟庆国，罗勤慧，沈孟长（南京大学配位化学研究所，配位化学国家重点实验室南京，２１００９３）关键词铜锌超氧化物歧化酶，吸附，循环伏安，双阶跃计时电量超氧化物歧化酶是超氧离子（·Ｏ）...     

汞电极上氢析出反应速度理论计算

本文根据量子电化学的热活化模型和肖特基效应,得到了电流密度-过电势关系式,计算了汞电极上氢析出反应速度。计算值与文献测量值基本一致。     

Adsorption from a Layer of Finite Thickness on a Planar Electrode

Within the Nernst diffusion model, the effect the convection has on the adsorption at a planar electrode is studied for the case of a diffusion-controlled stage of adsorption and the behavior of the Frumkin–Melik–Gaikazyan finite adsorption impedance is analyzed. Allowing for the convection leads to new functional frequency dependences of constituents of this impedance at low frequencies, where the active constituent depends on the diffusion layer thickness more heavily than the capacitive one. During adsorption of neutral molecules from a layer of finite thickness, an additional relaxation time emerges in an electrochemical system, which results from a finite rate of motion of species in the near-electrode layer. Ignoring the convection may lead to erroneous interpretation of the adsorption mechanism.     

Simulating Unstable States during the Coumarin Adsorption on a Mercury Electrode

Dependences of differential capacitance C on potential E of a stationary electrode (hanging mercury drop) in aqueous 0.1 M NaF solutions containing 4.6 × 10^–4 to 3 × 10^–3 M C₉H₆O₂ are obtained using an automatic impedancemeter. At coumarin concentrations below 0.001 M and potential slowly scanned near –1.1 V (SCE) the capacitance is unstable, which results in differently-shaped C vs. E curves in this potential range. The obtained results are attributed to nonequilibrium phase transitions in the adsorption layer, during which the orientation of coumarin molecules at the electrode surface alters. These phenomena are explained semiquantitatively on the basis of a developed theory.     

Anion Electroreduction on a Dropping Mercury Electrode in the Presence of Condensed Layers of Organic Substances

Methods of polarization and chronoamperometric measurements are used to investigate the electroreduction of the BrO¯₄ anions on DME. For the first time it is established that this process, which requires that a donor of protons should take part in it, proceeds at a finite rate on CAL of 1-adamantanol and thymine. The obtained data testify that the BrO¯₄ electroreduction, which obeys a slow-discharge mechanism in the absence of a CL, in the presence of such a layer is characterized by absolutely different regularities, which are intrinsic to electrochemical processes involving a preceding slow chemical stage. The assumption is made that such a stage may be the restructuring of the hydration sphere of BrO¯₄ at the CL/solution interface, which leads to the formation of complexes with the participation of water molecules bound with adsorbed molecules of surface-active organic substances through hydrogen bonds.     

Ni-Sn电极析氢性能研究

在Fe基底材料上电镀Ni_Sn合金制备低析氢过电位的阴极活性材料 .该材料适用于氯碱工业隔膜型电解槽 ,可达到降低槽压、节能降耗的目的 .在电解槽阴极溶液NaOH 12 0 g/L ,NaCl190 g/L ;温度 90℃ ,阴极极化电流密度i=15 0mA/cm2 的条件下 ,测得其析氢过电位为 88mV .X射线衍射分析表明 ,该种材料与传统装饰用Ni_Sn合金的结构状态有所不同 .采用循环伏安法对Fe电极和Ni_Sn合金电极进行分析 ,可初步判断Ni_Sn合金对氢的吸附较弱 ,有利于析氢反应的进行     

从银电极上氢析出的温度效应得到的反应动力学启示

利用循环伏安法研究了多晶银电极在0.1 mol/L HClO4溶液中氢析出反应的温度效应. 发现当从析氢起始电位负向扫描至零电荷电位（-0.4 V）时,氢析出反应的表观活化能（Ea,app）和指前因子（A）均随着电势的负移而增大（对应的Ea,app从24 kJ/mol增大至32 kJ/mol）.继续负向扫描至零电荷电位以后,Ea,app随电势的负移而减小但A不随电势变化. 推测Ea,app和A在零电荷电位前的反常变化来自于反应物和过渡态之间内能和熵值变化．在零电荷电位以正电位,电极附近的水分子以氧端吸附在电极表面上,且水分子之间有氢键作用。电势变化产生的能量主要用于使水分子脱附并使氢键网络改变．在E〉PZC的电位区,电位负移导致的正的熵效应（指前因子增加）补偿了活化能的升高导致的负效应,从而显示反应的净电流随电位负移而增加．结果表明溶剂的动力学和相关的熵因子项可能会对析氢这类涉及质子和电子转移的电极反应的动力学产生很大的影响．     

Kinetics of Adsorption of Neutral Molecules from a Thin Layer on a Rough Electrode

A theoretical model for the generalized finite adsorption impedance of a rough electrode is offered. A complex function of the roughness of the electrode surface is introduced and its frequency dependence is studied. The frequency characteristics of constituents of the adsorption impedance are shown to depend on the electrode roughness and the diffusion layer thickness. The frequency dependences of the phase angle and impedance components are found to considerably differ from the Frumkin–Melik-Gaikazyan result for an ideal smooth electrode.     

Electroreduction of Anions and Silver Kryptate on a Mercury Electrode in Conditions of Adsorption of Kryptate Complexes

Electroreduction of persulfate, hexacyanoferrate, and perbromate anions on a mercury electrode is studied in conditions of individual adsorption of kryptate complexes of cations and in the case of their co-adsorption with surface-active substances that form two-dimensional condensed layers on the electrode/solution interface. The electroreduction dramatically accelerates during both individual adsorption of kryptate complexes and their co-adsorption with 1-adamantanol, due to an electrostatic effect. The behavior of electrochemically active kryptate complexes is investigated by studying the Ag⁺ kryptate. In the system studied the [Ag⁺ 222] complex undergoes diffusion-controlled reduction.     

Determining Sodium Kryptate Adsorption Parameters on a Mercury Electrode in 1 M Na2SO4

The adsorption of a complex of sodium cations with a macrocyclic ligand (Kryptofix^R 222, composition C₁₈H₃₆N₂O₆) as a function of its concentration in 1 M Na₂SO₄ is studied by measuring the differential capacitance on a stationary Hg drop. Adsorption parameters of sodium kryptate are found using a regression analysis method and various versions of a model of two parallel capacitors complemented with the Frumkin adsorption isotherm. The differential capacitance curves, calculated on the basis of these, are compared with experimental data. The difference in model versions that most adequately describe the adsorption data, established for systems in 0.1 and 1 M Na₂SO₄, is explained by the influence of the supporting electrolyte on the adsorption layer structure. Conclusions are made on the absence in the system under study of the salting-out from the bulk solution and on a change in the properties of an adsorption layer of sodium kryptate in the region of potentials of the anodic adsorption–desorption peak following expansion of the adsorption region.     

New Analysis of Data on the Differential Capacitance of a Mercury Electrode during the Adsorption of tert-Butanol

A regression analysis of data on the differential capacitance of a mercury electrode in aqueous solutions of tert-butanol, which were published previously, is performed. It is shown that, in contradistinction to an analogous analysis of electrocapillary curves (ECC), in order to describe the adsorption of this compound in the framework of a model of two parallel capacitors, it is necessary to take into account the linear dependence of the parameter of an intermolecular interaction on the electrode potential. It is established on the basis of modeling calculations that, in order to obtain the same result in the case of a regression analysis of ECC, the relative accuracy of measurements of the interfacial tension must be two orders of magnitude the relative accuracy of measurements of the differential capacitance.     

电解水新型Ni-S析氢电极的研制

电解水新型Ｎｉ－Ｓ析氢电极的研制①袁孝友＊（安徽大学化学化工学院合肥２３００３９）王金玉（哈尔滨工业大学应用化学系哈尔滨１５０００１）大规模工业化电解水制Ｈ２始于本世纪３０年代．进入７０年代,西方国家就将Ｈ２作为能源列入开发计划．欧共体于１９７６年制...     

Relaxation of the Adsorption with Charge Transfer: The Iodide Ion Adsorption on a Platinum Electrode

The relaxation of the iodide ion adsorption on platinum electrodes with smooth and developed surfaces is studied in the time range 10^–4to 10³s and frequency range 10^–3to 10⁵Hz. Mathematical models matching experimental data to within the experimental accuracy are designed. Most adsorption centers on platinum have relaxation times > 0.1 s. The fraction of adsorption centers with > 100 s increases on the electrode with the developed surface, and in the ranges t< 0.1 s and F> 2 Hz, characteristics of this electrode are almost completely defined by the surface porosity. It is discovered that the electrode surface becomes smoother, leading to a slow drift of characteristics with time.