硝基苯的电还原特性研究

采用准稳态极化、循环伏安、线性扫描和恒电位阶跃等测试方法,对Ｈ２ＳＯ４溶液中硝基苯的电还原特性进行研究,评价了硝基苯在Ｃｕ、Ｃｕ－Ｈｇ和Ｃｕ－Ｎｉ电极的电还原反应活性,研究了硝基苯电还原为ＰＡＰ的中间步骤,并对反应机理进行了探讨。结果表明,硝基苯在酸性介质中的电还原反应存在中间步骤,并伴有反应物吸附现象,硝基苯电还原反应受硝基苯及其还原产物在溶液中的液相传质步骤控制．     

酸性溶液中硝基苯在WC电极上的电化学还原

以聚四氟乙烯为粘接剂制成碳化钨(WC)电极.采用循环伏安法、线性扫描法和恒电位阶跃法研究了硝基苯在酸性溶液中WC电极上的电化学行为.实验表明:WC电极对硝基苯的还原具有较好的活性,电极过程受扩散和电化学步骤混合控制;表观活化能为23.7kJ·mol 1,其中,电化学步骤的活化能10.91kJ·mol 1.     

硝基苯与离子液体的相互作用对硝基苯电还原传递系数的影响

应用紫外光谱研究了离子液体和硝基苯的相互作用, 硝基苯的紫外光谱受离子液体的影响, 硝基的吸收峰红移, 末端吸收消失. 用循环伏安法研究硝基苯电还原过程中第2个电子转移的传递系数(α)随外界条件变化所呈现复杂的变化规律. 硝基苯和水的介电性质、硝基苯和水与离子液体的相互作用对α产生复杂影响. 硝基苯浓度增加使α减小, 离子液体的咪唑侧链增长也使α减小. 相同硝基苯浓度时, 水的浓度较低时, α随水的浓度增加变小; 水的浓度较高时, α随水的浓度增加稍微变大. 温度升高α值增大.     

硝基苯在离子液体EMimBF4中的选择性电还原

采用循环伏安法和恒电位电解法研究了离子液体EMimBF4中硝基苯在微铂电极上的选择性电还原特性. 研究结果表明, 硝基苯在铂电极上的电还原反应为双分子八电子三步骤电化学过程: 第一步反应为准可逆单电子转移步骤, 产生阴离子自由基; 第二步为二电子转移步骤, 并伴有随后的双分子不可逆自由基偶合反应和快速质子化及脱水反应, 主要产物为氧化偶氮苯; 第三步是二电子转移产生偶氮苯的过程. 通过控制电位, 可以选择性地合成氧化偶氮苯和偶氮苯; 在EMimBF4中, 硝基苯和水的浓度变化对电化学行为产生较大影响.     

Electrochemical Reduction Characterizations of Aromatic Nitro-Compounds

In this paper, the electrochemical reduction characterizations of the aromatic nitro-compounds including nitrobenzene, α-nitronaphtahlene and l,5-dinitroanthraquinone in the sulfuric acid solution were investigated and the reaction mechanism was proposed as well. The electrochemical measurements such as cyclic voltammetry, quasi-steady-state polarization, fast linear potential sweep and chronoamperometry were carried out by using EG&G 273A electrochemical measurement system. The results showed that three compounds could be reduced electrochemically to the corresponding aminophenol confounds under the suitable reaction conditions on Cu-Hg cathode. The reduction peak potential was all in the range of -0.4 to -0.6 V (vs. SCE) for the above confounds. The corresponding specific surface activity energy tested was 21.5, 16.4 and 21.2 kJ/mol respectively, means the better electrochemical reduction activity on Cu-Hg electrode. Further investigation on the reaction mechanism disclosed that α-nitronaphtahiene and 1,5-dinitroanthraquinone have the similar reaction mechanism to that of nitrobenzene to para-aminophenol, i.e.,Bamberger rearrangement courses. With the increasing of the number of benzene number, the temperature and the concentration of needed for the electrochemical reduction increased correspondingly, i.e.,90℃ for nitrobenzene, 110℃ for α-nitronaphtahlene and 140℃ for l,5-dinitroanthraquinone respectively. The reaction rates are proportional to the concentration of the reactants the corresponding conditions.     

硝基苯在铜电极上的电还原特性研究

应用循环伏安法和线性扫描伏安法研究水溶液中硝基苯在铜电极上的电还原特性及其电还原为苯胺的中间步骤和反应机理.结果表明:铜电极上硝基苯的还原电位在-0.58V和-1.32V左右(vs.SCE),溶液的酸性和碱性均有益于该还原反应的发生;还原过程伴有反应物吸附现象,当硝基苯浓度较大时,还原过程受传质过程控制;随着厌氧程度的提高,还原速率加快.     

Cu/C-Nafion复合电极上硝基苯的电化学还原

制备性电解的结果表明，硝基苯在Cu／C－Nafion膜复合电极上的还原产物只有苯胺，可能与电极／Nafion界面的弱酸性环境和其还原中间产物本羟胺在界面的扩散较仅有关．生成苯胺的电流效率随电流密度的增大而减小，随反应液中硝基苯浓度的增大出现一个最大值．这可能是硝基苯的电化学还原过程受某种粒子的扩散控制、峰电流取决于硝基苯在Nafion膜中的溶解度所致．     

暂态电化学表面增强拉曼光谱研究对硝基苯硫酚分子的电化学还原过程

对硝基苯硫酚是表面增强拉曼光谱研究中最常用的探针分子之一,对硝基苯硫酚在电极表面电化学还原反应的研究有助于对芳香族硝基化合物还原机理的认识. 本文应用暂态电化学-表面增强拉曼光谱技术,研究了对硝基苯硫酚在循环伏安和计时电流法过程中的表面增强拉曼光谱. 结果表明,实验实现了完全与电化学检测时间分辨率同步的表面增强拉曼光谱检测,以最快5毫秒的时间分辨率研究了对硝基苯硫酚分子在金电极表面的还原过程. 结果分析推测其此反应过程极快,在5毫秒的时间分辨率下仍难以捕获其中间物种. 本研究为人们更深层次研究和认识硝基苯类化合物电化学还原过程提供了参考和方向.     

纳米氧化锡在锌-硝基苯电池反应中的电催化

以氯化锡为原料,四丙基溴化铵为表面活性剂水热法制备纳米二氧化锡（SnO₂）催化剂,并以钛网为基材,制备催化电极. 应用SEM,XRD等手段对催化剂进行表征. 考察了反应物浓度、反应温度和反应时间对催化剂形貌的影响. 研究了纳米SnO₂催化剂对锌还原硝基苯原电池反应的电催化性能. 结果表明,当 NaOH浓度为0. 5 mol•L^-1、水热反应温度160 ℃、水热反应时间15 h时,得到的SnO₂催化剂是由纳米片构成的刺球状颗粒,粒径最小,约17 nm. 与平板铂电极相比,制备的催化电极对硝基苯电还原具有更高的催化活性,硝基苯转化率为74%,最大放电功率为21.9 mW•cm^-2,远大于平板铂电极. 硝基苯的主要还原产物为苯胺、对乙氧基苯胺和对氯苯胺.     

Electrochemical sensor for nitrobenzene based on carbon paste electrode modified with a poly(3,4-ethylenedioxythiophene) and carbon nanotube nanocomposite

A sensitive and selective electrochemical sensor for the determination of nitrobenzene (NB) was developed based on a carbon paste electrode (CPE) modified with a nanocomposite prepared from the conducting polymer poly(3,4-ethylenedioxythiophene) and carbon nanotubes. The modified CPE exhibits good conductivity, a large surface area, and excellent catalytic activity towards the electrochemical reduction of NB. Under optimal conditions, the modified CPE is capable of detecting NB in the 0.25 to 43 μM concentration range and with a detection limit at 83 nM. Moreover, the sensor is highly stable and reusable, and free of interferences by other commonly present nitro compounds. It was used to determine NB in wastewater samples.

检测硝基苯的类石墨氮化碳修饰电化学传感器研究

以三聚氰胺为原料,利用热缩聚法制备了类石墨氮化碳(g-C_3N_4),并采用X射线衍射(XRD)、扫描电镜(SEM)、红外光谱等方法对其进行表征。然后将g-C_3N_4超声分散于Nafion溶液中,将所得悬浊液修饰到玻碳电极上,制备用于检测硝基苯的电化学传感器(g-C_3N_4/Nafion/GCE)。采用循环伏安法、方波伏安法研究了硝基苯在该电极上的电化学行为。在优化实验条件下,硝基苯在该电极上的方波伏安还原峰电流与其浓度在4.0×10~(-6)~6.0×10-4mol/L范围内呈良好的线性关系,相关系数(r)为0.999 8,检出限为4.0×10~(-7)mol/L。按照国家标准方法对实际水样进行检测,未检测出硝基苯。配制两个浓度水平硝基苯的模拟水样进行加标回收实验,其回收率分别为102.1%和99.9%。用气相色谱法做对照实验,结果表明本方法与气相色谱法的测定结果无显著性差异。     

质子惰性介质中硝基苯在铂微盘电极上的电化学行为

采用循环伏安法, 以铂微盘电极为工作电极, 铂片为辅助电极, 饱和甘汞电极为参比电极, 研究了硝基苯在含有四丁基高氯酸铵(TBAP)电解质的N,N-二甲基甲酰胺(DMF)有机溶液中的电化学行为, 并探讨了扫描速度和底物浓度等因素对硝基苯电化学特性的影响. 结果表明,该反应属扩散控制的准可逆反应.     

铜-镍合金电极表面组成及状态的变化对硝基苯电还原的影响

铜-镍合金电极表面组成及状态的变化对硝基苯电还原的影响;Monel合金电极;表面状态;硝基苯;对氨基苯酚;电还原     

Novel electrochemical heterogeneous catalytic reactor for organic pollutant abatement

Taking nitrobenzene as a model, electrochemical heterogeneous catalytic degradation of organic pollutant is investigated using a novel electrochemical heterogeneous catalytic reactor coupled by three-dimensional electrode with heterogeneous catalytic reactor. The nitrobenzene removal efficiencies considerably depend on the applied potential, initial pH, and the concentration of the supporting electrolyte. The results show that, with catalyst the nitrobenzene removal efficiencies are higher than that of control (without catalyst). The efficiency of ferrous catalyst is the best for nitrobenzene removal especially. It is clear that the reaction of electro-oxidation is promoted by the catalyst. A possible mechanism of nitrobenzene degradation is deduced based on products. Published in Russian in Elektrokhimiya, 2007, Vol. 43, No. 3, pp. 313–318. The text was submitted by the authors in English.     

Photocatalytic Reduction of Nitrobenzene by Titanium Dioxide Powder

The feasibility of photocatalytic reduction of nitrobenzene using titanium dioxide powder as photocatalyst, under the protection of nitrogen and presence of hole scavenger conditions, was studied. Effects of the illumination time, amount of catalyst and sorts of solvent on the photocatalytic reduction of nitrobenzene were investigated, respectively. The results showed that, for the photocatalytic reduction of nitrobenzene, aniline was the main product. When the illumination time was 6 h, 8.15×10^?4 mol/L of nitrobenzene could be photocatalytically reduced completely, with the yield of aniline being 88.5%. The optimum amount of TiO₂ used was 4.0 g/L, the optimum initial pH value of reaction solution was 4.0 and the best solvent was methanol. The kinetics and mechanisms of the photocatalytic reduction of nitrobenzene were also discussed.     

Investigation of the oxidation of hydroquinone at the liquid/liquid interface

<正>The oxidation of hydroquinone(QH_2) was investigated for the first time at liquid/liquid(L/L) interface by scanning electrochemical microscopy(SECM).In this study,electron transfer(ET) from QH_2 in aqueous to ferrocene(Fc) in nitrobenzene (NB) was probed.The apparent heterogeneous rate constants for ET reactions were obtained by fitting the experimental approach curves to the theoretical values.The results showed that the rate constants for oxidation reaction of QH_2 were sensitive to the changes of the driving force,which increased as the driving force increased.In addition,factors that would affect ET of QH_2 were studied.Experimental results indicated ion situation around QH_2 molecule could change the magnitude of the rate constants because the capability of oxidation of QH_2 would be affected by them.     

Employment of a useful liquid membrane electrode system to characterise the micelles of bile salts and other detergents in pure and mixed states

Ion-pairs or coacervates (formed by the reaction between cationic and anionic surfactants) dissolved in nitrobenzene can behave as surfactant-ion registering devices to respond to both surfactant cation and anion. The complexes of cetyltrimethyl ammonium bromide with sodium dodecyl sulfate, sodium salts of deoxycholic and chenodeoxycholic acids, and Aerosol Orange T have been used in nitrobenzene to generate such useful liquid membranes. The complex of dimethyldioctadecyl ammonium bromide and sodium cholate has been used to study the cholate ion behaviour since its complex with cetyltrimethyl ammonium bromide is water soluble. The electrochemical behaviours of the liquid membranes have been found to be fairly good and reproducible. The membrane potential measurements have been used to determine the critical micelle concentrations of the surfactants in pure as well as in mixed states to evaluate surfactant—surfactant interaction in the micelles of the latter.     

锂电池Li／KIBr2—非水体系的研究

本非水电池体系由Ｌｉ负极、多孔石墨电极和电解质溶液组成；电解质溶液由无机溶剂ＰＯＣｌ＿３（或有机溶剂硝基苯）和溶解在该溶剂中的活性物质（ＫＩＢｒ＿２）及支持电解质构成。该电池体系的开路电压为８．５０伏左右，放电性能良好，可望在实际中得到应用。此外，对电池体系的反应机理也作了初步的探讨。     

血红蛋白在碳纳米管修饰碳糊电极上的直接电化学行为

利用吸附法将血红蛋白(Hb)固定在碳纳米管修饰碳糊电极表面,制成稳定的固载Hb碳纳米管修饰电极,研究了Hb在碳纳米管修饰电极上的直接电化学行为.固载Hb的碳纳米管修饰电极在pH=7.0的PBS（磷酸盐缓冲溶液）中有一对相当可逆的循环伏安氧化还原峰,为Hb血红素辅基Fe(Ⅲ)/Fe(Ⅱ)电对的特征峰.式电位为－0.160 V(vs SCE),随扫描速度变化很小.电子转移数为1.021,近似为一个辅基发生电子转移.Hb在碳纳米管修饰电极表面的电子转移常数为0.0816 s－1,远大于亚甲蓝作媒介体时Hb的电子转移反应速率常数.应用于过氧化氢、三氯乙酸和硝基苯等的电催化还原,固定在碳纳米管修饰碳糊电极的血红蛋白表现出稳定且较高的催化活性.     

Ionic Liquid‐Hemoglobin‐Carbon Paste Composite Bioelectrode and Its Electrocatalytic Activity

A new carbon ionic liquid paste bioelectrode was fabricated by mixing hemoglobin (Hb) with graphite powder, ionic liquid 1‐ethyl‐3‐methylimidazolium tetrafluoroborate (EMIMBF₄) and liquid paraffin homogeneously. Nafion film was cast on the electrode surface to improve the stability of bioelectrode. Direct electrochemistry of Hb in the bioelectrode was carefully investigated. Cyclic voltammetric results indicated that a pair of well‐defined and quasi‐reversible electrochemical responses appeared in pH 7.0 phosphate buffer solution (PBS), indicating that direct electron transfer of Hb was realized in the modified electrode. The formal potential (E^0′) was calculated as ?0.316 V (vs. SCE), which was the typical characteristic of the electrochemical reaction of heme Fe(III)/Fe(II) redox couple. Based on the cyclic voltammetric results the electrochemical parameters of the electrode reaction were calculated. This bioelectrode showed high electrocatalytic activity towards the reduction of trichloroacetic acid (TCA) with good stability and reproducibility.