硫化黑2BR 200%在石墨镀银电极上的电催化还原

采用涂附法制备了石墨镀银电极。用配有EDS的扫描电子显微镜(FE-SEM)对石墨镀银电极表面结构进行了表征,以石墨镀银电极和石墨电极为工作电极,采用线性扫描法研究了硫化黑在NaOH溶液中的电化学还原行为,探讨了溶液pH值对硫化黑2BR 200%电还原反应的影响。实验结果表明：用涂附法制备得到的石墨镀银电极表面分布了大量金属银颗粒,该石墨镀银电极对硫化黑2BR 200%的还原反应显示了很高的电催化活性,其电催化活性高于石墨电极;电解液的pH值越大,硫化黑的电还原反应就越容易。在恒电流电解中,以镀银石墨电极为阴极,电流密度为6.25 mA•cm^-2,反应温度为(27±2)℃时,硫化黑的电解实验的电流效率可达92.2%。     

二氧化碳在银电极上发生电还原反应时的电极失活原因

在KHCO3水溶液中,利用线性扫描、塔菲尔曲线、恒电位电解、电化学阻抗谱方法,研究了CO2在银电极上发生电还原反应的动力学特征,发现当电解反应进行一段时间后,阴极表面生成了一层棕黑色物质附着在电极表面,导致生成CO的平衡电位负移,交换电流密度变小,电荷转移电阻增大,电流效率和电流密度迅速降低。用X射线光电子能谱(XPS)分析了有害物质的主要成分,证明阴极表面附着物主要为石墨碳和微量Zn,这些物质附着在阴极表面,导致电极失活,阻碍CO2电还原反应继续进行。     

活性氧化镍电极电催化合成二甘醇酸

通过电化学氧化还原技术将镍电极进行活化制备活性氧化镍电极,结合AFM、循环伏安和恒电流电解等技术研究了二甘醇在NaOH溶液中电催化氧化合成二甘醇酸。结果表明,经活化后的镍电极对二甘醇具有较高的电催化活性,镍电极经15 min活化处理后的电催化活性最佳。获得的最佳电解工艺条件为：电流密度17 mA·cm^-2,电解反应温度60℃,二甘醇浓度0.3 mol·L^-1,NaOH浓度2 mol·L^-1,此时二甘醇酸的收率为66.7％,电流效率为66.1％,二甘醇的转化率达89％。     

电化学法合成对苯二胺

在乙醇的酸性溶液中以Ｃｕ为阴极，电解还原对硝基苯胺合成对苯二胺。文中考查了温度、电流密度、对硝基苯胺的深度等因素驿对苯二胺的产率及电流效率的影响。在本文介绍的最佳条件下，对苯二胺的最大产率为９４．６％。     

水杨酸阴极还原为水杨醛的研究

本文用循环伏安法和极谱法对水杨酸阴极还原为水杨醛进行了研究。结果表明：水杨酸阴极还原为水杨醛是不可逆的；阴极材料必须是汞或汞齐化的高氢电压电极材料；阴极电解液必须加入Ｈ＿３ＢＯ＿３和ＮａＨＳＯ＿３；电解液温度应控制在１７℃；在Ｃｕ－Ｈｇ齐电极上水杨酸的还原电位为－１．６Ｖ，在Ｐｂ－Ｈｇ齐电极上其还原电位为－１．５Ｖ。我们用Ｃｕ－Ｈｇ齐为阴极的离子交换膜电解槽对水杨酸进行恒电位电解，紫外吸收光度分析法分析电解液中水杨醛含量为０．１２Ｍ／ｌ，转化率为７５％，电流效率达６０％     

间接电氧化媒质Ce4+/Ce3+的循环与再利用

设计了一种适用于间接电氧化合成反应,中试规模的填充式隔膜电解槽.该电解槽以铜板为阴极,PbO2/Ti石墨颗粒填充电极为阳极,电解液[0.16mol/L Ce2(SO4)3,1.5 mol/L H2SO4]采用外循环的方式控制其温度为30～50℃,在50A/m2的电流密度下电解,获得大于80%的电流效率.讨论了电极材料、电流密度、电解液温度、Ce3+浓度和循环次数等对电流效率的影响.其中Ce3+浓度是限制电流密度和影响电流效率的主要因素;电解液在间接电氧化对甲氧基甲苯反应中连续循环使用20次,仍然保持高于85%的电流效率;PbO2/Ti石墨颗粒填充电极使用寿命超过6个月.     

电合成法制备纳米材料及纳米材料电极上的电催化合成

通过电化学合成前驱体直接水解法制备纳米TiO2 粉体和纳米TiO2 膜电极。用循环伏安法、循环方波伏安法和电解合成法研究了纳米TiO2 膜电极对有机合成反应的电催化活性。发现纳米TiO2 膜电极在 0 2～ - 1 2V扫描电位区间有两对氧化还原峰 (峰电位Epc1=- 0 5 6V ,峰电位Epc2 =- 0 95V ,扫描速度 10 0mV·s-1) ,具有异相氧化还原催化行为。电解结果表明 ,纳米TiO2 膜中的Ti(Ⅳ ) /Ti(Ⅲ )氧化还原电对作为媒质 ,异相间接电还原硝基苯为对氨基苯酚 (收率91 6 % ,电流效率 95 2 % )和草酸为乙醛酸 (收率 96 5 % ,电流效率 90 % )。     

对硝基苯酚在铜电极上的电化学还原过程研究

采用循环伏安法研究了不同pH溶液中对硝基苯酚在铜电极上的电化学还原行为,选定了不同的电位利用计时电流法电解对硝基苯酚。研究了对硝基苯酚电解还原过程中pH、电位和电解时间对去除效率的影响,并对反应机理进行了探讨。结果表明,对硝基苯酚在铜电极上能发生还原反应,并且随着pH的升高,还原电位负移。     

N-(2-甲基)苯基羟胺的合成新工艺

[目的]N-(2-甲基)苯基羟胺是一种重要农药中间体,用选择性还原方法进行合成。[方法]以邻硝基甲苯为主要原料,经Raney Ni-水合肼还原制备N-(2-甲基)苯基羟胺。[结果]在优化的反应条件下,N-(2-甲基)苯基羟胺的反应收率为78.5%。加入适量SiO~2颗粒后,反应收率可达90.2%。补加适量催化剂后,Raney Ni可套用1次。由于N-(2-甲基苯基)羟胺在空气中不稳定,尝试了进一步与氯甲酸甲酯反应制备N-羟基-N-2-甲苯氨基甲酸甲酯,2步总收率85.7%(含量为98.2%),其结构经氢谱核磁分析确证。[结论]N-(2-甲基)苯基羟胺合成工艺具有生产成本低、收率高和易于工业化生产等优点。     

改性海藻酸钠／壳聚糖双极膜成对电解制备乙醛酸

以镍网电极-改性海藻酸钠/壳聚糖双极膜(Ni-mSA/mCS BM)作为阴阳两室间的隔膜,利用双极膜的中间界面层水解离特性成对电解制备乙醛酸.水解离特性分析结果表明,双极膜中水解离后生成的H 透过mSA阳离子膜进入阴极室中,可及时补充草酸电还原生成乙醛酸过程中的H 消耗;OH(透过mCS阴离子膜进入阳极室中,与乙二醛电氧化生成乙醛酸过程中产生的H 结合生成H2O,可促进正向反应的速度.以饱和草酸和盐酸的混合液作阴极液,以10%乙二醛和10%KBr的混合液作阳极液,镍网为阴极,二氧化铅为阳极,在电流密度为20 mA·cm-2常温下电解,阴极电流效率达82.9%,阳极电流效率达75.7%,电解电压低于2.7 V.     

电化学还原硝基甲烷合成N-甲基羟胺盐酸盐的工业化试验

An industrial electrolytic cell was designed for the electrochemical synthesis of N-methylhydroxylamine hydrochloride （N-MHA）. Copper was used as the cathode, graphite as the anode, and a cation membrane as the separator. The results show that N-MHA with a high purity of 99% can be electrosynthesized directly from nitromethane in HC1 solution. Under a constant current of 1000-2500A.m^-2 in the temperature of 30-50℃, the average yield, current efficiency, and reaction selectivity were 65%, 70%, and 99%, respectively. Graphite electrode and membrane material can be used continuously in the preparative electrolysis for 5000h. Moreover, the effects of the electrode and membrane materials, current intensity, electrolyte temperature, and other associated parameters on the electrosynthesis results were investigated. The direct current power consumption was 8151.3kW-h-（1000kg N-MHA）^ -1. This method is a simple separation process with limited contamination and hence, is a new green synthesis method for the industrial production of N-MHA.     

Electrosynthesis of N-methylhydroxylamine

N-methylhydroxylamine is an important intermediate for the synthesis of phenylmethoxyureas. Its synthesis by electroreduction of nitromethane is an easy process which can be carried out in aqueous acidic medium in a divided filter press cell with Monel, nickel, stainless steel and lead cathodes and DSA^® anodes separated by a cation exchange membrtane. Faradaic and chemical yields are higher than 95%. The product may be isolated as the HCl salt. Due to the mild operating conditions, high yields and low environmental impact, the process is a very good alternative to the current industrial methods of synthesizing this product, mainly for low-quantity production plants.     

几种多孔电极材料镓电沉积性能的研究

在工业上,稀散金属镓通常是从碱性溶液中电解提取得到的。在镓电解过程中,由于析氢副反应和传质速率低的原因导致镓电沉积的电流效率很低。本工作采用三维多孔电极电沉积镓,利用三维多孔电极发达的表面积促进镓电沉积过程,研究了不同电极材料(泡沫金属和多孔碳)的析氢特性,结合不同电解温度和电流密度下各材料的镓电沉积行为,揭示三维多孔电极上镓电沉积的特性规律。结果表明,泡沫铜和石墨毡(GF)具有较低的析氢活性,但两种电极的镓电沉积性能差别很大。其中泡沫铜表现出最佳的镓电沉积性能,在温度为40℃、电流密度为0.1 A/cm²条件下镓电沉积的电流效率(QE)达到22.5%,远高于铜片电极(10.7%);而相同条件下,GF电极的QE值仅为9.6%,低于铜片,这与电极表面的疏水性有关。具有较高析氢活性的泡沫铁、泡沫镍和网状玻璃碳(RVC)电极的镓电沉积过程受电解温度和电流密度的影响较大。在高电流密度下,泡沫铁电极表现出仅次于泡沫铜的QE值,在低电流密度下难以发生镓的电沉积;泡沫镍和RVC电极仅在低于镓熔点(20℃)的条件下发生镓的电沉积,在高于镓熔点(40℃)的条件下,由于电沉积的液态镓...     

Surface-modified electrodes for NADH oxidation in oxidoreductase-catalysed synthesis

Three surface-modified electrodes were investigated: 3,4-dihydroxybenzaldehyde electropolymerized on glassy carbon, hexacyanoferrate modified nickel electrodes, Meldola Blue adsorbed on graphite, for application to NADH oxidation in oxidoreductase-catalysed synthesis. The high overpotential, which is generally required for NADH oxidation on clean electrodes, was perfectly overcome with the three electrodes and especially with the Meldola blue modified graphite electrode. This electrode allowed fast NADH oxidation at potentials as low as 0.00 V vs SCE. It also ensured good storage stability. It is stressed that the key problem in applying this electrode to synthesis is the decrease in its electrocatalytic properties under operating synthesis conditions. An operating procedure was established that allowed ageing of the electrode to be directly linked to the current measurement. Following this procedure, several methods were investigated for improving the half-life of the electrode: pulse electrolysis, replacing NADH by NAD⁺ in the initial solution, lowering the NAD⁺ concentration and using dextran-bound NAD⁺. In the best conditions, the half-life reached 152 min instead of 34 min with the initial conditions, proving that fouling by anodically produced NAD⁺ was first of all identified as a very important cause of electrode ageing. Modification of intrinsic surface properties of the electrode also led to the decrease of the interface efficiency.     

Electrochemical removal of nitrate ions in waste solutions after regeneration of ion exchange columns

Electrochemical reduction of nitrate ions in synthetic regenerating solutions after ion exchange column regeneration was studied. The influence of current density on the current efficiency was determined in the range 2.8–7.6 mA cm–2 in a diaphragmless flow-through electrolyser in a batch recirculation mode. A Cu cathode and a Ti/Pt anode was used, the temperature being maintained at 25 C. Highest integral current efficiency occurred at 2.8 mA cm–2. The presence of about 6 mg dm–3 Cu ions in treated solution was found to prevent a decrease in cathode activity and, consequently, in electrolysis efficiency. The catalytic influence of Cu ions was verified by potentiodynamic polarisation experiments on a copper rotating disc electrode and by chronopotentiometry performed during the course of electrolysis.     

对氨基苯酚的绿色电化学合成及其工业化

研究了在阴极转动分隔式电解槽中硝基苯电化学还原制备对氨基苯酚（PAP）时阴极转速、反应温度等工艺参数对电解性能的影响,并考察了不同阳极材料的稳定性.实验结果表明,增大阴极转速和升高反应温度有利于反应的进行;自制的Pb-Sb-Sn-Ag-Cu五元合金作为阳极材料具有比Ti/Ir阳极更长的工作寿命.当以铅合金为阳极材料、体系温度为90℃、阴极转速为900 r•min^-1、电解电流为3000 A时,硝基苯的平均转化率为99%,PAP平均收率为69.9%,电解直流电单耗为7.24 kW•h•(kg PAP)^-1,产品纯度大于98%,熔点为186.1～187.3 ℃.     

电化学氧化法制取烟酸的研究进展

介绍了直接电氧化法和间接电氧化法制取烟酸的原料及相应的电极反应,同时对直接电氧化法制取烟酸的电解槽、电极材料、离子交换膜及支持电解质等的研究进展进行了评述。直接电氧化法多采用Pt、PbO2和PbO2/Ti为阳极,Pb和Ni为阴极,离子交换膜为隔膜,电流效率可达70%。     

Electrochemical process for 2,4-D herbicide removal from aqueous solutions using stainless steel 316 and graphite Anodes: optimization using response surface methodology

In this experimental study, an electrochemical cell (100 cc) equipped with anode electrodes of SS316 and graphite and the cathode electrode of SS316 in parallel form at a distance of 1 cm from each other was used to degradation the 2,4-Diclorophenoxy acetic acid (2,4-D) herbicide. The results showed that the removal efficiency of 2,4-D herbicide in initial concentrations of 50 and 100 mg/L under optimum conditions (pH = 7, electrolysis time = 50 min and current density = 3 mA/cm²) using the graphite anode electrode was 73.5% and 47.76%, respectively; however, using the SS316 electrode, the removal efficiency was 44.23% and 17.65%, respectively. The highest removal of 2,4-D in electrochemical process was 95.87% for herbicide initial concentration of 50 mg/L by graphite anode electrode. Considering the efficiency of 2,4-D removal, the determined coefficients were found to be 0.91–0.93. The amount of energy consumed for SS316 and graphite electrodes was obtained to be 6.308 and 5.99 kWh/m³, respectively. Results revealed that the electrochemical process with graphite anode electrode has an acceptable efficiency in removing the 2,4-D herbicide and can be used as an appropriate pretreatment in treating the wastewater containing the resistant compounds such as phenoxy group herbicides (2,4-D).     

Electrochemical etching using surface carboxylated graphite electrodes in ultrapure water

Electrochemical etching enables processing with an atomic-level accuracy, without deteriorating the physical properties of the workpiece; however, contamination of its surface with electrolytes is unavoidable. If it is possible to carry out electrochemical etching without using electrolytes, such a process will be applicable to electronic device manufacturing and precision nanoscale processing of semiconductor materials. In addition, this process does not require the use of chemicals, cleaning after processing or disposal of waste fluid, which results in a low-cost and environmentally friendly process. To develop an electrochemical etching process that does not require the use of electrolytes, we proposed a method in which a functional-group-modified electrode is used as the cathode. A carboxylated graphite electrode was prepared by treating a graphite electrode with sulfuric acid. Electrolysis of ultrapure water was carried out using the obtained electrode as a cathode. The results indicate that the electrolysis current obtained using the modified electrode is approximately six-fold that obtained using an unmodified electrode. Furthermore, we can etch a Cu surface conically in ultrapure water. The current efficiency increases by 70% at maximum, and the minimum current required for electrochemical etching decreases compared with that in the case of using an unmodified electrode.     

Electrochemical deposition and characterization of NiFe coatings as electrocatalytic materials for alkaline water electrolysis

In this study, nickel (Cu/Ni), iron (Cu/Fe) and nickel-iron (Cu/NiFe) composite coatings with various chemical compositions were electrochemically deposited on a copper electrode and characterized using cyclic voltammetry (CV), atomic absorption spectroscopy (AAS), scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques in view of their possible applications as electrocatalytic materials for the hydrogen evolution reaction (HER) in an alkaline medium. The electrocatalytic activity of the coatings for the HER was studied in 1 M KOH solution using cathodic current-potential curves and electrochemical impedance spectroscopy (EIS) techniques. The presence of nickel along with iron increases the electrocatalytic activity of the electrode for the HER when compared to nickel and iron coatings individually. The HER activity of the composite coatings depends on the chemical composition of the alloys. The Cu/NiFe-3 electrode (with a molar concentration ratio of Ni²⁺:Fe²⁺ of 4:6 in the plating bath) was found to be the best suitable cathode material for the HER in an alkaline medium under the experimental conditions studied. Furthermore, the electrocatalytic activity of the Cu/NiFe-3 electrode for the HER was tested for extended periods of time in order to evaluate the change in the electrocatalytic activity of the electrode with operation time. The HER was activation controlled and has not been changed after electrolysis. A constant current density of 100 mA cm⁻² was applied to the electrolysis system, and the corrosion behavior of the Cu/NiFe-3 electrode was investigated after different operation times using EIS and linear polarization resistance (LPR) techniques. For comparison, the corrosion behavior of a Cu/NiFe-3 electrode to which current was not applied was also investigated. The corrosion tests showed that the corrosion resistance of the Cu/NiFe-3 cathode changed when a cathodic current was applied to the electrolysis system.