零电流示波电位滴定的研究 Ⅰ.非配偶型铂电极上的螯合滴定:EDTA滴定金属离子

(一)前言螯合电位滴定是电位滴定的一个主要组成部分,文献极为丰富。这些滴定主要是在金属电极和离子选择电极上进行的。金属电极分为两类:配偶型和非配偶型。配偶型电极如Pt/Fe~(3+);Fe~(2+)、Hg/Hg~(2+);HgY~(2-);MY~(n-4)M~(n+),其“电极/溶液”界面上总有一对决定电位的电对。非配偶型电极的界面上则不存在明显的电对,如铂电极上EDTA滴定Ca~(2+),溶液中不外加高价的铂离子;滴定Fe~(3+),也不外加Fe~(2+)。关于非配偶型电极上的螯合滴定,虽有     

两铂电极零电流示波双电位滴定法

本文提出了用阴极射线示波器荧光屏上荧光点的显著位移来指示零电流双电位滴定终点的新方法, 并对其特点进行了研究. 新的终点指示方法能响应两电极间ΔE的瞬时变化, 因而比常用的方法灵敏, 扩大了两铂电极零电流双电位滴定的应用范围.     

示波双电位滴定法的研究——硫化硒中硒的测定

示波双电位滴定法在氧化还原滴定中的应用已有报导.运用一大一小两个铂电极为指示电极,在没有任何外加电流的情况下,滴定终点时体系中氧化还原电位响应的差别导致荧光屏上光点的突然移动。以此指示终点比示波极谱滴定中切口的变化更为敏锐,比一般的电位滴定法更简便、直观。     

双铂电极交流示波电位滴定法

将两个同样大小的铂电极插入被滴定溶液中,让一个很小的交流电流通过两个电极并用示波器直接观察两极间的电位差(图1),荧光屏上出现一条荧光线,用荧光线的突然收缩或伸长指示滴定终点,这种简易的电滴定方法称为双铂电极交流示波电位滴定法。     

两Ag-TPB电极上的零电流示波双电位滴定法

将银片(或碳棒、铂片等)依次浸入Na-TPB及AgNO_3溶液中,得到用于示波电位滴定的Ag-TPB电极。在这种电极上进行双电位滴定。并用示波器直接指示⊿E的变化,确定滴定终点。方法简便灵敏,且可用于药物分析。     

比较电位法控制终点自动电位滴定仪的制作与应用

比较电位法控制终点是自动电位滴定仪中应用较多的确定滴定终点的方法。首先预定某一电位为终点电位,滴定至电极体系电位达到预定值时,滴定自动停止。为提高分析操作自动化水平,降低分析成本,我们用国产元器件制作了一台普及型比较电位法控制终点的自动电位滴定仪。该仪器结构简单,性能稳定,组装调试容易,成本低,易于数字化,且输入阻抗高,可与各种电极配合进行电位滴定。它能控制滴定速度,并自动检测滴定终点。     

碳糊电极电位滴定法滴定氯(Ⅰ)

氯元素是人体液中重要组成部分,Cl~-浓度对人体健康有很大影响.因此,国际上饮用水质标准为含Cl~-200mg/L.目前碳糊电极广泛应用于有机物的测定,但测无机离子的工作尚少,还没有人用碳糊电极作为滴定氯离子的指示工具.目前传统电分析方法是Ag电极为指示电极,但银电极价格较贵.本文首次采用碳糊电极(不含活性物质)电位滴定Cl~-,终点电位变化明显、直观.     

双修饰电极零电流示波双电位滴定的研究——混合酸的连续滴定

本文采用双聚苯胺修饰电极进行示波双电位滴定,用示波器直接指示△E的变化,以示波器荧光屏上荧光点最大位移指示终点。方法简便、快速、直观,用于乙二醛母液中混合酸的连续滴定,结果满意。     

银电极上氯溴碘的零电流示波双电位滴定

用阴极射线示波器荧光屏上荧光点的突然位移指示银电极双电位滴定终点,具有灵敏度高、简便、经济、快速等特点,比经典双电位滴定法优越,还可用于氯溴碘的连续滴定。     

一种最简单的电滴定方法——两铂电极示波电位滴定法

利用阴极射线示波器荧光屏上示波图的突变来指示双电位滴定终点的电化学滴定法称为示波双电位滴定法。最简单的示波双电位滴定法称为零电流示波双电位滴定法。这种滴定法可在两个铂电极上进行,也可在两个银电极或两个其它金属电极上进行。在两个铂电极上进行的零电流示波双电位滴定法简称为两铂电极示波电位滴定法。两铂电极示波电位滴定法的装置见图1。将一大一小两     

扫描电化学显微镜直接电沉积法构建葡萄糖氧化酶微米点

利用自制的凹形电极在铂基底电极上直接构建了葡萄糖氧化酶微米点. 首先, 将电聚合和电化学刻蚀法相结合制备了凹形铂微米电极. 然后将此种电极作为参比及辅助电极, 基底铂电极作为工作电极, 利用葡萄糖氧化酶在合适的条件下(浓度、一定量Triton X-100存在、电极电位等)由于电极表面pH的降低可以在铂电极上电沉积这一特性, 将酶固定在铂基底电极上, 微修饰得到了具有活性的葡萄糖氧化酶微米点. 最终用扫描电子显微镜和扫描电化学显微镜对所得微米点进行了表征. 所得微米点直径约20 μm, 且具有催化活性. 该方法简便, 干扰因素较少.     

球型Pt微粒电极的构建及其对甲醇电氧化的研究

以镍铬合金为基体,在其表面电化学沉积制备了Pt微粒电极,用扫描电子显微镜（SEM）对电极的表面形貌进行了表征,电化学方法考察了电极的电化学性能和甲醇在该电极上的电催化行为．结果表明镍铬合金表面沉积的球型Pt微粒电极对甲醇的电氧化具有良好的催化活性,相同实验条件下,该电极的催化活性比纯Pt电极高30倍．该电极对甲醇的电氧化显示出较高的催化性能．     

新型光化学电池高活性铂电极的研究

应用循环伏安法，在导电玻璃表面沉积微量铂，制备新型光电化学电池的高比表面高洁性对电极所获得的电极比表面最高达371m2·g-1;同时发现，该电极对的质量交换电流密度随铂沉积量的增加而减小，而相对于宏观面积的交换电流密度几乎没有变化，因此，在实验可控制的限度内，用微色的铂就可以获得高活性的对电极     

Electrochemical synthesis of self-doped polyaniline and its use to the electrooxidation of ascorbic acid

Self-doped polyaniline (PAN) film on platinum electrode surface has been synthesized via electrochemical copolymerization of aniline with orthanilic acid (OAA). Fourier transform infrared, UV–Vis, and elemental analysis indicate the formation of the copolymer and that the copolymer has the structure of a head-to-tail coupling of aniline and OAA units. It was found that the internal doping of PAN with OAA can extend the electroactivity of PAN in neutral and even in alkaline media. The obtained self-doped PAN (PAN-OAA)-coated platinum electrode is shown to be a good surface for the electrooxidation of ascorbic acid (AA) in phosphate buffer solution of pH 7. The anode peak potential of AA shifts from 0.63 V at bare platinum electrode to 0.34 V at the PAN-OAA-modified platinum electrode with greatly enhanced current response. A linear calibration graph is obtained over the AA concentration range of 5–60 mM using cyclic voltammetry. Rotating disk electrode voltammetry and chronoamperometry have been employed to investigate the electrooxidation of AA. The PAN-OAA-modified platinum electrode shows good stability and reproducibility.     

Electrocatalysis by ad-atoms: Part IV. Enhancement of the oxidation of formic acid on Pt-Au(subs) and Au-Pt(subs) electrodes by bismuth ad-atoms

The roles of surface and bulk for electrocatalysis have been investigated. Bi ad-atoms enhance a platinum electrode to a great extent for HCOOH oxidation. In order to examine whether bulk platinum atoms are necessary for the electrocatalysis, monolayer or submonolayer amounts of platinum atoms were made to deposit on a gold electrode which is quite inactive for the oxidation. The deposition of a complete monolayer of platinum atoms on a gold electrode makes the electrode as active as a platinum electrode itself. Bi ad-atoms enhance this electrode to the same extent as they do a platinum electrode for the oxidation. Thus surface atoms, Pt and Bi atoms, having no bulk atoms on a quite inactive electrode work effectively for the electrocatalysis, the platinum atoms for the adsorption of the main reactant and the Bi atoms for blocking of the sites against the formation of poison. It is the adsorptive property of the surface that controls the electrocatalytic activity.     

A study of electrodes used in controlled-potential electrolysis of metal ions

Various electrodes used in controlled-potential electrolysis of metal ions are discussed: (1) a double-junction saturated calomel reference electrode with sodium formate as bridge electrolyte; (2) an auxiliary electrode made by winding platinum wire on a Teflon cylinder; (3) a working electrode made of tantalum gauze. The advantages of the tantalum electrode over a platinum electrode are that the hydrogen overpotential is higher, and the tantalum electrode need not be precoated with copper before deposition of metals such as Bi, Zn and Sn, which tend to form alloys with platinum. The electrode needs pretreatment before use, but this takes only 4 min or less.     

甲酸在钼青铜修饰铂电极上的催化氧化

应用循环伏安法和双电位阶跃法研究了不同浓度硫酸中钼酸盐在多晶铂电极上的电化学行为 .在硫酸溶液中 ,当电位负向扫描时 ,钼酸盐即于铂电极上还原形成钼青铜 ,吸附在电极表面 ;电位正向扫描时钼青铜将再被氧化 ,氧化机理受硫酸浓度的影响 .铂电极因钼酸盐的还原和钼青铜的氧化而得到修饰 .在硫酸钠溶液中以此修饰的铂电极对甲酸氧化有明显的催化作用 ,其氧化峰电流接近未修饰铂电极上的 2倍 .钼青铜对铂的不完全修饰或过分修饰均会减弱甲酸氧化的催化作用     

乙醇在不同介质中电氧化的原位表面增强拉曼光谱研究

采用常规电化学伏安技术和电化学原位表面增强拉曼光谱(in-situ SERS)技术研究了不同介质中乙醇在粗糙铂电极上的电催化氧化行为. 发现不论在酸性、中性还是碱性介质中, 乙醇均能在粗糙铂电极上自发氧化解离生成强吸附中间体CO; 碱性介质中, CO在粗糙铂电极上基本氧化完全的电位(0.20 V)比中性和酸性介质中(0.50 V)负移了约0.30 V. 而乙醇在粗糙铂电极上CV正向扫描的氧化峰电位(-0.20 V)比酸性介质中(0.65 V)负移了约0.85 V. 比较不同介质中乙醇和CO在粗糙铂电极上的氧化峰电流和峰电位可以发现, 粗糙铂电极在碱性介质中对乙醇和CO的电催化氧化活性比中性和酸性介质中更强; 可以推测, 不论在酸性、中性还是碱性介质中, 乙醇在粗糙铂电极上的氧化过程均按双途径机理进行.     

Nanostructure Pt Electrode Obtained via Self-assembly of Nanoparticles on Conductive Oxide-coated Glass Substrate

Self-assembly of platinum nanoparticles were applied to fabrication of counter electrode for dye-sensitized solar cells on conductive oxide-coated glass substrate. The present Pt electrode exhibits high exchange current density of 220 mA/cm^2, which is comparable to those prepared by electrodeposition, magnetron sputtering or thermal decomposition of platinum chloride. After analysis by transmission electron microscopy (TEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS), it was found that the catalyst was structurally characterized as nanosized platinum metal clusters and was continuously arranged on electrode surface. The present nanostructure electrode had high electrocatalytic activity for the reduction of iodine in organic solution.     

Electrochemical oxidation of benzaldehyde and hydroxybenzaldehydes in acetonitrile on platinum and glassy carbon electrodes

The electrochemical oxidation of benzaldehyde and four hydroxybenzaldehydes was studied on platinum and glassy carbon electrodes in acetonitrile. A considerable difference was observed in electrooxidation performed on platinum and glassy carbon electrodes. All hydroxy derivatives fouled the glassy carbon electrode, but platinum was passivated only by the electrooxidation of 3-hydroxybenzaldehyde, highlighting the crucial role of the position of the substituent relative to the hydroxy group. On the glassy carbon electrode, the formation of the corresponding benzoyl radical could have taken place, which promoted the buildup of polymers on the electrode surface.