Mechanism and kinetics of the reduction of In(III) ions at a polycrystalline gold electrode from highly concentrated ZnCl2 solutions

Summary The mechanism of the cathodic reduction of In(III) at gold has been studied by rotating disc and ring-disc voltammetry in highly concentrated aqueous ZnCl₂ solutions. At concentration of the base electrolyte higher than 7 mol dm^–3, the voltammetric curves recorded at the disc electrode split into two well-separated waves which correspond to the successive charge transfer reactions: In(III) + 2e^– In(I) and In(I) + e^– In. By the use of coulometric and potentiometric techniques, the formal potentials of the In(III)/In(I), In(III)/In and In(I)/In redox couples as well as the equilibrium constants of the reproportionation reaction In(III) + 2 In 3 In(I) has been determined and discussed. The kinetic parameters of the In(III)/In(I) electrode reaction have been also evaluated and discussed.

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Mechanismus und Kinetik der Reduktion von In(III)-Ionen an der Goldelektrode in hochkonzentrierten wäßrigen ZnCl₂-Lösungen

Zusammenfassung Es wird der Mechanismus der Reduktion von In(III)-Ionen in hochkonzentrierten ZnCl₂ Lösungen mittels der Scheiben- und Ring-Scheiben-Elektrode aus Gold untersucht. Wenn die Konzentration des Grundelektrolyten 7 mol dm^–3 übersteigt, verteilen sich die erhaltenen Stromspannungskurven auf zwei gut gestaltete Stufen, die den konsekutiven Durchtrittsreaktionen In(III) + 2e^– In(I) und In(I) + e^– In entsprechen. Aufgrund der coulometrischen und potentiometrischen Messungen werden die Formal-Standardpotentiale der In(III)/In(I)-, In(III)/In-und In(I)/In-Redoxpaare, die Gleichgewichtskonstanten der Reproportionierungsreaktion In(III) + 2 In 3 In ermittelt. Die kinetischen Parameter der Durchtrittsreaktion In(III)/In(I) werden bestimmt und diskutiert.

     

高容量超级电容器电极材料的设计与制备

超级电容器寿命长,安全性高,并可以实现快速充放电,是化学电源研究的热点之一。然而,超级电容器的能量密度较低限制了其更多的应用。因此,超级电容器领域的研究关注点在如何提高超级电容器的能量密度。其中,提高比容量是提高能量密度的一种有效途径。本文通过对电极材料和电解液的优化来研究制备得到高容量超级电容器的方法。电极材料的比表面积、孔道结构和导电性对其电化学性能有着直接的影响。一方面,通过优化电极材料的孔道结构和比表面积可以增加活性位点并提高电解液离子传导率,从而得到高比电容。另一方面,电极材料导电性的提高有利于提升其电子传导率从而得到较高的比容量。本文分别对碳材料和金属氧化物/氢氧化物的优化达到了增加双电层电容和赝电容的目的。不仅如此,还可以通过在电解液中增加氧化还原电对从而得到高比电容。这一方法为高容量超级电容器的制备提供了新的思路。     

Surface modification by graphene oxide:An efficient strategy to improve the performance of activated carbon based supercapacitors

An efficient and cost-effective strategy to modificate the surface of active carbon (AC), form a 3D-conductive network, and therefore improve the electrochemical performance of AC based supercapacitor was developed.     

Modification of Carbon Paste Electrode Based on Molecularly Imprinted Polymer for Electrochemical Determination of Diazinon in Biological and Environmental Samples

The wide use of pesticides can lead to environmental and human adverse effects. Diazinon, as an organophosphorous pesticide, is used in agriculture because of its low cost and high efficiency on insects. Due to the increasing application of pesticides, accurate analytical methods are necessary. The aim of this work was modification of carbon paste electrode composition and applying it as a sensor for determination of diazinon in biological and environmental samples. Multi‐walls carbon nanotubes and a molecularly imprinted polymer were used as modifiers in the sensor composition. A molecularly imprinted polymer and a non‐imprinted polymer were synthesized for applying in the electrode. After optimization of electrode composition, it was used to determine the analyte concentration. Instrumental parameters affecting the square wave voltammetric response were adjusted to obtain the highest current intensity. The modified electrode with MIP showed very high recognition ability compared to the electrode containing NIP. The obtained linear range was 5×10⁻¹⁰ to 1×10⁻⁶ mol L⁻¹. The detection limit of the sensor was 1.3×10⁻¹⁰ mol L⁻¹ and the relative standard deviation for analysis of target molecule by the proposed sensor was 2.87 %. This sensor was used to determine the diazinon in real samples (human urine, tap, and river water samples) without special sample preparation before analysis. The optimization of electrode composition containing mentioned modifiers improved its response considerably.     

从电化学和微生物学角度分析微生物燃料电池处理硫污染物的机理

微生物燃料电池(Microbial fuel cells,MFCs)是一种有前景的去除废水中硫污染物的技术。本文在生物膜电极反应机理的基础上,讨论电极反应和微生物在MFCs处理硫污染物过程中的作用,论证了其处理机制和影响因素,总结了反应器构型、分离器类型、电极材料和催化剂,以及硫的回收和电极再生。此外,通过核算对比MFCs和典型的厌氧生物技术处理含硫废水的成本和收益对MFCs去除废水中硫污染物的可行性进行了评估。     

Ammonium Determination in Water Samples by Using Opa-Nac Reagent: A Comparative Study with Nessler and Ammonium Selective Electrode Methods

A selective and sensitive method based on the ammonium derivatisation with o -phthaldialdehyde (OPA) and N -acetyl-cysteine (NAC) has been developed for ammonium determination in real water samples. The proposed procedure has been compared with ammonium reference methods such as Nessler reagent method and ammonium selective electrode. All procedures have been chemometrically tested and compared in terms of the main analytical properties. These procedures have been used to determine ammonium in unknown water samples. The OPA-NAC reagent method does not present any systematic error (proportional or constant), while Nessler reagent presents both of them for some samples assayed. The ammonium selective electrode is free of corrigible systematic errors, however presents amine interference. The OPA-NAC ammonium method is able to achieve a detection limit (LOD) of 0.07 mg/L in the sample, with a linear dynamic range up to 1.4 mg/L of ammonium.     

Practical Study into Enhancing IgG Immobilisation on Screen-Printed Electrodes for Environmental Applications

This work is focused on the influence of pH and applied potential for the immobilisation of rabbit IgG on a carbon screen-printed electrode. The orientation of IgG molecule at the surface is fundamental for activity and reproducibility of the immunosensor. As the electrode potential is increased a particular order may be brought to the immobilised antibodies, i.e. the antibodies adapt a more favourable arrangement on the surface to facilitate better binding. The response increased when changing the pH from basic to acidic medium and the reverse trend was observed for the limit of detection (LOD). When a potential was applied to the electrode, the response generally decreased and the LOD increased in the order acidic > basic > neutral pH. The LODs obtained from antibodies immobilised at acidic pH and + 100 mV were better than the LODs obtained at other conditions.     

基于含锌有机配位聚合物的微孔碳的合成及其电化学性能

报道了一种基于含锌(II)有机配位聚合物制备微孔碳的新方法. 通过锌离子和酒石酸之间的配位作用获得含锌有机配位化合物, 并通过氢键作用将其引入到间苯二酚/甲醛低聚物溶胶的开放网络结构中. 使含锌有机配位化合物和酚醛低聚物溶胶体系发生共聚反应得到酚醛和含锌有机配位共聚物, 在950℃下热处理分解以及锌蒸气蒸发后制得微孔碳. 微孔碳材料典型样品具有相对较大以及比较规则的微孔, 其比表面积可以达到1260 m²·g^-1, 孔体积为0.63 cm³·g^-1. 所得微孔碳作为超级电容器电极材料的等效串联电阻为0.46 Ω, 其循环伏安曲线展示出较好的矩形性. 恒流充放电分析结果表明, 当电流密度为1 A·g^-1时, 微孔碳电极的比电容为196 F·g^-1; 在10 A·g^-1的大电流密度下, 比电容仍然达到137 F·g^-1. 该电极具有优良的循环稳定性, 1000次循环后比电容保持率达到98%. 这一研究结果表明, 所得微孔碳在超级电容器电极材料方面具有重要的应用前景.     

聚吡咯/海藻酸钠纳米球的制备及其应用于高性能超级电容器

用海藻酸钠作为结构导向剂,通过原位氧化聚合吡咯法制备了聚吡咯/海藻酸钠(PPy/SA)纳米球.聚吡咯/海藻酸钠纳米球的形貌和结构通过扫描电镜(SEM)、X射线衍射(XRD)和傅里叶变换红外(FTIR)光谱进行表征.材料的电化学性能通过循环伏安法和恒电流充放电方法进行测试.电化学测试表明,聚吡咯/海藻酸钠纳米球在1 mol L-1KCl电解液中,电流密度为1 A g-1时其比电容高达347 F g-1.与纯聚吡咯相比较,聚吡咯/海藻酸钠纳米球具有更优异的循环稳定性能.     

(PtAuPt)HN/GC的制备及对甲酸氧化的电催化性能

以Se溶胶为模板,合成了多层核壳结构的Se@Pt@Au@Pt实心纳米粒子;采用化学与电化学相结合的除硒方法制得了(PtAuPt)HN/GC,并表征了(PtAuPt-Se)HN的表面形貌、结构与组成;以甲酸为探针分子,比较了(PtAuPt)HN/GC和Pt/C/GC对甲酸氧化的电催化行为,发现(PtAuPt)HN/GC催化甲酸氧化只有1个氧化峰,峰电位和峰电流分别约为0.35V和1.22mA/cm2,而Pt/C/GC则有2个氧化峰,在0.35V时所对应的电流密度仅约为0.30mA/cm2,前者在该电位时的电流密度是后者的4倍;在0.30mA/cm2的电流密度下,(PtAuPt)HN/GC对应的电极电位为0.01V,比Pt/C/GC负移了340mV;在600s时的计时电流分别为0.06和0.02mA/cm2.(PtAuPt)HN对甲酸氧化的电催化活性不但比Pt/C高,而且具有一定的抗CO中毒性能.