铂微粒修饰聚苯胺膜电极对甲酸电催化氧化的研究

采用循环伏安法研究Pt盘电极 (Pt)、铂微粒修饰Pt盘电极 [Pt(Pt) ]和Pt微粒修饰聚苯胺膜电极 [PAN(Pt) ]对甲酸电催化氧化行为的影响 ,比较了它们对甲酸电催化氧化的活性 ,发现PAN(Pt)电极对甲酸电催化氧化的表观电流密度为 3 79× 10 2 mA·cm-2 ,分别比Pt、Pt(Pt)和Pt-PDMA/Pt电极约高 2 35、2 5和 6 3倍。峰电位比Pt PDMA/Pt电极约低 0 16V。     

纳米TiO_2膜电极上乙醛酸的电催化合成研究

运用电化学循环伏安法 (CV)对纳米TiO2 膜电极 (Ti/nano TiO2 )在硫酸和草酸溶液中的电化学行为进行了研究。在c(H2 SO4 ) =1mol/L溶液中的循环伏安图上Epac1=- 0 .5 6V(vs.SCE)和Epac2 =- 0 96V(vs.SCE)处 ,出现两对可逆氧化还原峰 ,而在相同扫描速度下草酸溶液中的循环伏安曲线上 ,这两对电极反应氧化峰基本消失 ,还原峰电流增大 ,表明Ti/nano TiO2 膜电极对电还原草酸成为乙醛酸的反应具有较高的电催化活性和选择性。常温常压下 ,控制电位Epc=- 1 0V左右电解合成乙醛酸 ,乙醛酸的产率和电流效率分别达到 96 5 %和 90 %。     

Pt/H_xMoO_3电极上甲醇的催化氧化

铂电极在c(K2 PtCl6) =2 .5× 10 -3 mol/L、c(Na2 MoO4 ) =0 .0 5mol/L、c(H2 SO4 ) =0 .5mol/L的溶液中 ,电位为 +1 1～ - 0 2V(vs.SCE) ,以 2 0mV/s的速度循环扫描 10min ,可制得一种Pt/HxMoO3 电极。用循环伏安和电位阶跃方法研究了在所制备电极上甲醇的氧化。实验结果表明 ,所制备电极对甲醇的氧化有催化作用 :(1)氧化电位比在Pt/Pt电极上降低 0 12 5V ;(2 )氧化电流为Pt/Pt电极的 6倍。讨论了Pt/HxMoO3 电极对甲醇氧化的催化机理。     

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 % )。     

纳米TiO2-Pt修饰电极的制备、性能及应用

采用电化学合成法和电沉积法制备高活性钛基纳米TiO₂-Pt(Ti/nano-TiO₂-Pt)修饰电极,通过循环伏安法研究并比较了钛基纳米TiO₂膜电极、纯Pt电极、Ti/nano-TiO₂-Pt电极在H₂SO₄溶液中的电化学行为以及Ti/nano-TiO₂-Pt电极对Mn²⁺氧化为Mn³⁺的电催化性能.结果表明纳米TiO₂-Pt修饰电极对Mn²⁺的电氧化有高催化活性.Mn²⁺氧化峰电位为1.28 V（vs SCE）,比纯Pt电极负移0.12 V;析氧电位为1.40 V,比纯Pt电极高0.08 V.Ti/nano-TiO₂-Pt修饰电极催化性能优于纯Pt电极和纳米TiO₂膜电极,非均相电解氧化效率可达90%以上.电解得到的Mn³⁺可一步氧化甘油为甘油醛,收率为96%.     

甲醇在聚苯胺载铂电极上的电催化氧化

用循环伏安法在玻碳电极上电聚合导电高分子聚苯胺用于附载Pt，提高了Pt的分散度。发现甲醇在Pt／PAN／GC电极和Pt／GC电极上均能自发解离出强吸附中间体CO，证实聚苯胺膜的存在有利于提高电极对甲醇的电催化氧化活性，CO在Pt／PAN／GC电极上的氧化峰电流明显高于Pt／GC电极。通过比较甲醇的电催化氧化活性可知，Pt/PAN／GC电极催化氧化甲醇的峰电流为58．68mA/cm^2和50．00mA／cm^2，是Pt／GC电极氧化峰电流的1．6倍和1．7倍。     

PAN/GO包覆改性C/MnO_2合成锂离子电池负极材料及性能研究

本文以碳基二氧化锰(C/MnO_2)为前驱体,用聚丙烯腈(PAN)/氧化石墨烯(GO)包覆改性前驱体合成锂离子电池负极材料。通过XRD、XPS、SEM对材料进行结构形貌表征。结果显示,复合材料为氮、碳基锰氧化物,随包覆物PAN和GO含量减少,复合材料由颗粒嵌入平整膜转变为褶皱纱状覆盖颗粒物;在PAN/GO与C/MnO_2包覆比例为3:3时,碳化改性制备的复合材料电极有最优充放电性能,在200 A g~(-1)电流密度条件下,经过100次循环后放电比容量为447 m Ahg~(-1)。     

电化学法制备纳米TiO_2聚邻甲苯胺复合膜

用 3mol·L- 1 酸作为介质 ,扫描速度为 10 0mV·s- 1 ,扫描电位为 - 0 1～ 0 8V ,用循环伏安法在纳米二氧化钛 (Nano TiO2 )膜电极上实现了邻甲苯胺 (o MA)的电化学聚合 ,并对制得Nano TiO2 聚邻甲苯胺 (P -o MA)复合膜的电化学性质进行了研究。结果表明 :在峰电位 (Ep)为 0 .5 6V处有一个明显的氧化峰 ,在Ep 为 0 .5 8、0 .30和 - 0 .0 4V处分别有一个还原峰 ,经长时间扫描 ,氧化峰电流可达到 5 0A·dm- 2 以上 ,具有工业应用价值。同时实验也表明 ,复合膜的生成、Ip 和Ep 的大小受溶液浓度、扫描速度 (v)以及扫描电位的影响     

PAN,Cu~(2+)-PAN配合物的电化学性质研究

采用循环伏安法分别研究了PAN和Cu~(2+)-PAN配合物在玻碳电极上的电化学性质。在pH=6.2的NaOH-KH_2PO_4介质中,扫速为50m V/s时,PAN有一对氧化还原峰,其E_(pa)=0.011 V,E_(pc)=-0.026 V。Cu~(2+)能和PAN形成配位比为1∶1的配合物,并在-0.328 V处出现一不可逆的特征还原峰,且峰电流由中心离子Cu~(2+)还原产生。同时求算了PAN和Cu~(2+)-PAN配合物在玻碳电极上的电化学参数,并讨论了反应机理。     

硬脂酸二茂铁酯L—B膜修饰SnO2电极的阻抗研究

测定了二茂铁衍生物——硬脂酸二茂铁酯L-B膜修饰SnO_2电极在Fe(CN)_6~(3-/4-)溶液中的阻抗性能,用单纯形法求出了等效电路中的元件参数值,计算了电极反应速度常数K_s。从分析SnO_2电极修饰不同层的硬脂酸二茂铁酯L-B膜的界面阻抗和电极反应的动力学性能,表明与在固相中研究的硬脂酸二茂铁酯L-B膜的阻抗性能明显不同,在Fe(CN)_6~(3-/4-)溶液中表现了电活性分子修饰电极的界面阻抗行为,进一步证实了修饰在SnO_2电极上的硬脂酸二茂铁酯L-B膜在Fe(CN)_6~(3-/4-)的氧化还原电极反应过程中,起电荷传递的中介作用。     

The electrocatalytic oxidation of ascorbic acid on polyaniline film synthesized in the presence of β-naphthalenesulfonic acid

Polyaniline-β-naphthalenesulfonic acid composite film on platinum electrode surface has been synthesized via the electrochemical polymerization of aniline in the presence of β-naphthalenesulfonic acid (NSA). FT-IR, UV-vis and electrochemical characterization indicate the formation of the doped polyaniline. Further investigations found that the polyaniline (PAN) doped with NSA extended the electroactivity of PAN in neutral and even in alkaline media. The PAN-NSA composite film coated platinum electrodes are shown to be good electrocatalytic surfaces for the oxidation of ascorbic acid (AA) in phosphate buffer solution (PBS) of pH 7.0. The anode peak potential of AA shifts from 0.62 V at bare platinum electrode to 0.34 V at the PAN-NSA composite 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. The kinetics of the catalytic reaction is investigated using rotating disk electrode (RDE) voltammetry, cyclic voltammetry and chronoamperometry. The results are explained using the theory of electrocatalytic reactions at chemically modified electrodes. The PAN-NSA composite film on the electrode surface shows good reproducibility and stability.     

循环伏安法电沉积镍-钴-磷/泡沫镍电极及其析氢催化活性研究

以泡沫镍(NF)为基体,采用循环伏安(CV)电沉积法制备Ni-Co-P/NF催化电极,电沉积液组成和工艺条件为:NiSO4·6H2O 0.07 mol/L,CoSO4·7H2O 0.03 mol/L,NaH2PO2·H2O 0.6 mol/L,扫描电位区间−0.6~−1.2 V(相对于饱和甘汞电极),扫描速率0.01 V/s,扫描14次。采用扫描电镜(SEM)和能谱仪(EDS)分析了电极的表面形貌和元素组成。通过阴极极化曲线和塔菲尔斜率对比了NF、Ni-P/NF和Ni-Co-P/NF电极在1 mol/L NaOH和0.5 mol/L H2SO4溶液中的析氢催化活性,并通过循环伏安和电流密度−时间曲线测试了电极的稳定性。结果表明,Ni-Co-P/NF电极在碱性和酸性条件下都表现出优于Ni-P/NF的析氢活性和稳定性。     

Redox poly[Ni(saldMp)] modified activated carbon electrode in electrochemical supercapacitors

The complex (2,2-dimethyl-1,3-propanediaminebis(salicylideneaminato))-nickel(II), [Ni(saldMp)], was oxidatively electropolymerized on activated carbon (AC) electrode in acetonitrile solution. The poly[Ni(saldMp)] presented an incomplete coated film on the surface of carbon particles of AC electrode by field emission scanning electron microscopy. The electrochemical behaviors of poly[Ni(saldMp)] modified activated carbon (PAC) electrode were evaluated in different potential ranges by cyclic voltammetry. Counterions and solvent swelling mainly occurred up to 0.6 V for PAC electrode by the comparison of D^1/2C values calculated from chronoamperometry experiments. Both the Ohmic resistance and Faraday resistance of PAC electrode gradually approached to those of AC electrode when its potential was ranging from 1.2 V to 0.0 V. Galvanostatic charge/discharge experiments indicated that both the specific capacitance and energy density were effectively improved by the reversible redox reaction of poly[Ni(saldMp)] film under the high current density up to 10 mA cm⁻² for AC electrode. The specific capacitance of PAC electrode decreased during the first 50 cycles but thereafter it remained constant for the next 200 cycles. This study showed the redox polymer may be an attractive material in supercapacitors.     

Study of the hypophosphite effect on the electrochemical reduction of nitrobenzene on Ni

The effect of the hypophosphite ion on the electrochemical reduction of nitrobenzene on Ni was evaluated from a cyclic voltammetric study and from constant potential electrolysis in an aqueous-ethanol alkaline medium. The results were compared with the data obtained in an hypophosphite-free solution. It was found that in an hypophosphite containing solution an unusual selective reduction of nitrobenzene to nitrosobenzene occurs. It is the first time that nitrosobenzene is detected as the reaction product of the nitrobenzene electrochemical reduction in an aqueous-ethanol solution. It is proposed that the Ni modified surface which is formed upon hypophosphite oxidation is responsible for the non reducibility of nitrosobenzene. The effect of the electrode potential on the nitrobenzene electrolysis on a Ni modified electrode was analysed. It was concluded that the highest nitrosobenzene yield (33%) and selectivity (82%) is achieved at −1.1 V. It was also found that the formation of nitrosobenzene leads to an electrode poisoning effect in the electrolysis process.     

载铂聚苯胺/聚砜复合膜修饰电极对甲醇的电催化氧化行为研究

采用循环伏安法制备聚苯胺(PAN)/聚砜(PSF)复合膜修饰电极,在其上电沉积铂粒子,制得载铂聚苯胺/聚砜复合膜修饰电极,用循环伏安法和交流阻抗法研究它对甲醇的电催化氧化行为。复合膜的化学组分用FTIR进行表征,复合膜内层载铂后的表面形态用SEM进行表征。结果表明,复合膜的内层(与工作电极接触的一面)是聚苯胺,外层(与溶液接触的一面)是聚砜,铂粒子在复合膜内层的多孔聚苯胺上均匀沉积,从而使载铂聚苯胺/聚砜复合膜修饰电极对甲醇有好的电催化氧化性能。     

Thermal effects on the measurement of photocurrent at anodic films on nickel electrodes

The influence of heat on the measurement of photocurrents at nickel electrodes in a 1 M NaOH solution was investigated by using photocurrent, photothermal and thermal current methods under the irradiation of laser beams with wavelengths of 488, 532 and 632 nm, respectively. It was found that the photocurrent appeared in the potential (vs. Hg/HgO electrode) region lower than −0.1 V was caused by the p-type semiconductor property of Ni(OH)₂ anodic film. In the Ni(OH)₂/NiOOH redox potential region the appearance of photocurrent was likely caused by the local temperature variation rather than the semiconductor properties of the anodic layer. Similar phenomena was observed for β-Ni(OH)₂ electrode. During the light irradiation an increase of temperature at the surface of the working electrode may disturb the measurement of photocurrent.     

Green bio-synthesis of Ni/montmorillonite nanocomposite using extract of Allium jesdianum as the nano-catalyst for electrocatalytic oxidation of methanol

In this work, synthesis of Ni nanoparticles was carried out successfully by water extract of Allium jesdianum as a biochemical reducing agent in the presence of montmorillonite clay (MMT) as a natural solid support for the first time. Then the electrochemical activity of the synthesized nanocomposite was investigated in methanol electrocatalytic oxidation. MMT with high cation exchange capacity and nano layer structure was exposed to ion exchange conditions in nickel solution. Then Ni²⁺ ion exchanged form was used in this process as a source of ions and also capping agent. Water extract of Allium jesdianum used as a reducing agent due to abundant availability of phenolic and flavonoid contents. The synthesized Ni/MMT nanocomposite was characterized using UV-Vis spectroscopy (UV-Vis), Fourier Transform Infrared Spectroscopy (FT-IR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission electron microscopy (TEM) and Energy-dispersive X-ray spectroscopy (EDX). The surface of prepared modified electrode has been characterized using SEM to evaluate the morphology, showing uniform dispersion of Ni nanoparticles with mean diameter of 12 to 20 nm. The modified carbon paste electrode was then used in methanol electrocatalytic oxidation reaction. Methanol oxidation on the proposed modified electrode surface occurs at 0.6 V and 0.3 V in alkaline and acidic medium respectively. Also, the results showed the better performance of modified electrode toward methanol electrocatalytic oxidation in comparison with carbon paste electrode that is modified by ion exchanged MMT. Charge transfer coefficients and apparent charge transfer rate constant for the modified electrode in the absence of methanol in alkaline medium were respectively found as: α_a = 0.53, α_c = 0.37 and k_s = 1.6×10^-1 s^-1. Also, the average value of catalytic rate constant for the electrocatalytic oxidation of methanol by the prepared nano-catalyst was estimated to be about 0.9 L·mol^-1·s^-1 by chronoamperometry technique. The prepared electrode was also effective for electrocatalytic oxidation of ethanol and formaldehyde in alkaline medium.     

Electrodeposited MnO2/Au composite film with improved electrocatalytic activity for oxidation of glucose and hydrogen peroxide

The major drawback of currently used MnO₂ film sensor is the loss of electrical conductivity due to the formation of a poorly conductive MnO₂ layer. To overcome this problem, a coating in which the Au is alloyed with MnO₂ has been developed. The fabrication of the codeposited film electrode of Au and MnO₂ by using a cyclic voltammetric (CV) method was described, and systematic physical and electrochemical characterization was performed. This MnO₂/Au film electrode enhanced MnO₂ electrocatalytic activity. The oxidation process of glucose at the codeposited MnO₂/Au shows a well-defined peak at 0.27 V in alkaline aqueous solution. In contrast, the glucose oxidation at Au modified glassy carbon electrode (GCE) just shows a shoulder wave at 0.42 V. The experimental results indicate that the modification of MnO₂ on the surface of GCE significantly improved the electrocatalytic activity towards the oxidation of glucose. Further study shows that the MnO₂/Au could also effectively catalyze the oxidation of hydrogen peroxide in pH 7.0 phosphate buffer solution (PBS).     

Surface modification of Inconel-600 by growth of a hydrous oxide film

In this study, Inconel-600 (Ni–Cr–Fe alloy) was modified by repetitive potential cycling in 1M NaOH solution. This procedure induced the growth of a hydrous oxide film, following the same mechanism as previously reported for pure nickel in alkaline solution under similar experimental conditions. The electrode, modified by 30 repetitive potential cycles, exhibited about one order of magnitude lower current density in both the active and passive ranges of the anodic polarization curve. Selective dissolution of nickel and iron in acid solution was determined by rotating ring–disc electrode measurements. This process resulted in chromium enrichment as shown by use of X-ray electron spectroscopy. The proposed model for the enhanced stability of the modified electrode agrees with the percolation model of passivity of stainless steels and Fe–Cr alloys.