恒电位氧化改性石墨毡及其氧还原电极的电化学性能

分别采用循环伏安改性法和恒电位氧化法对石墨毡进行改性处理,并采用循环伏安法对其电化学性能进行研究,实验结果表明,恒电位氧化改性较循环伏安改性的石墨毡有较好的氧还原活性。通过XRD、FTIR、接触角和CV针对恒电位氧化处理石墨毡进行了进一步的测试。测试结果显示,随恒电位氧化时间的增加,石墨毡表面亲水性含氧官能团增加,润湿性增强。恒电位氧化改性处理25 min的石墨毡氧还原峰电位及电流密度分别为~-0.43 V和~0.003 4 mA·cm^-2,显示出很好的电化学催化性能。基于以上结果,恒电位氧化法改性处理能够极大提高石墨毡的氧阴极活性。     

恒电位氧化改性石墨毡及其氧还原电极的电化学性能（英文）

分别采用循环伏安改性法和恒电位氧化法对石墨毡进行改性处理,并采用循环伏安法对其电化学性能进行研究,实验结果表明,恒电位氧化改性较循环伏安改性的石墨毡有较好的氧还原活性。通过XRD、FTIR、接触角和CV针对恒电位氧化处理石墨毡进行了进一步的测试。测试结果显示,随恒电位氧化时间的增加,石墨毡表面亲水性含氧官能团增加,润湿性增强。恒电位氧化改性处理25 min的石墨毡氧还原峰电位及电流密度分别为~-0.43 V和~0.003 4 m A·cm~(-2),显示出很好的电化学催化性能。基于以上结果,恒电位氧化法改性处理能够极大提高石墨毡的氧阴极活性。     

过渡金属氧化物修饰石墨毡阴极及电催化氧化性能测试

采用H2O2化学预处理石墨毡,并将过渡金属氧化物Ce O2负载到石墨毡上,制备出复合石墨毡阴极材料。研究结果表明H2O2处理可增加石墨毡的含氧官能团,改善表面亲水性,进而提高Ce O2的负载量,XRD分析表明石墨毡表面负载的Ce O2为萤石结构。电化学阻抗谱(EIS)和循环伏安曲线(CV)分析表明修饰后的石墨毡电荷传输阻力变小,氧化还原电流强度显著增强,活性表面积增大8倍,线性扫描(LSV)实验表明改性石墨毡在氧还原过程中具有较大的电流密度,是未改性前的8.5倍。采用改性石墨毡作为阴极,进行电芬顿催化降解甲基橙测试,20 min脱色率达到96.8%,与未改性石墨毡相比,去除率提高133.2%,显著提高了其电催化氧化性能。     

过渡金属氧化物修饰石墨毡阴极及电催化氧化性能测试

采用H₂O₂化学预处理石墨毡,并将过渡金属氧化物CeO₂负载到石墨毡上,制备出复合石墨毡阴极材料。研究结果表明H₂O₂处理可增加石墨毡的含氧官能团,改善表面亲水性,进而提高CeO₂的负载量,XRD分析表明石墨毡表面负载的CeO₂为萤石结构。电化学阻抗谱(EIS)和循环伏安曲线(CV)分析表明修饰后的石墨毡电荷传输阻力变小,氧化还原电流强度显著增强,活性表面积增大8倍,线性扫描(LSV)实验表明改性石墨毡在氧还原过程中具有较大的电流密度,是未改性前的8.5倍。采用改性石墨毡作为阴极,进行电芬顿催化降解甲基橙测试,20 min脱色率达到96.8%,与未改性石墨毡相比,去除率提高133.2%,显著提高了其电催化氧化性能。     

氧化镉改性石墨毡作为高性能的钒电池负极

为了提高原始石墨毡(GF)对V3+/V2+氧化还原反应的电催化活性和降低析氢反应对电池性能的影响,本文采用水热法将氧化镉(CdO)纳米颗粒负载于石墨毡表面,制备出改性石墨毡(CdO/GF)作为高性能的钒电池负极。通过扫描电镜(SEM)、X射线衍射分析(XRD)进行表面形貌和物相分析得出:CdO纳米颗粒均匀负载于石墨毡纤维表面;线性扫描伏安法(LSV)、循环伏安测试(CV)、交流阻抗谱测试(EIS)表明:相对于GF,CdO/GF有效抑制了析氢反应的活性,CdO/GF对于V3+/V2+氧化还原反应的电化学活性和可逆性有显著的提高,电荷转移阻抗也有明显的减小;单电池测试中,对比GF,CdO/GF的放电容量衰减速率有显著的下降,在90 mA·cm-2的电流密度下的电压效率和能量效率提高了约5%。在多次充放电循环过程中,CdO/GF的催化性能显示出良好的稳定性。     

全钒氧化还原液流电池用石墨毡电极的分步氧化活化

石墨毡电极是组成钒电池的关键材料,其较低的电化学活性是造成钒电池功率密度较低的关键因素之一. 本论文采用一种简便的石墨毡电极分步氧化活化法,先将石墨毡在高锰酸钾溶液中进行氧化,后置于活化溶液中激发其反应活性. 通过对处理后的石墨毡进行循环伏安、交流阻抗测试、XPS以及SEM表征,发现氧化时间和活化溶液组成是影响电极性能的因素,在本文中,先经过3天氧化时间,后在配比为3:1的活化溶液中处理的电极,较其他方法处理的电极,电荷传递电阻明显降低,其与溶液之间的接触电阻最低,为7.33 Ω·cm ²,氧化还原峰值比更接近于1,有效提高了反应的活性与可逆性,经X射线光电子能谱分析发现性能提高的原因与表面含氧官能团数目增加有关. 单电池性能测试结果进一步证实,利用该方法处理的石墨毡为电极的单电池,较未经处理的电池相比性能更优,有更高的放电容量和能量效率,在100 mA·cm ^-2电流密度下,能量效率较未处理电极高出7.47%. 与热处理法、酸处理法及电化学氧化法相比较,该方法不需要辅助设备,不消耗能源.     

Dy（III）离子在LiCl-KCl熔盐中的电化学行为及Dy-Ni金属间化合物的选择性制备

采用循环伏安、方波伏安和开路计时电位等电化学方法研究了Dy(III)离子在LiCl-KCl共晶盐中的电化学行为及Dy-Ni合金形成的电化学机理.循环伏安和方波伏安法研究表明, Dy(III)离子的电化学还原过程为三个电子转移的一步反应.与惰性W电极相比, Dy(III)离子在Ni电极上的循环伏安曲线多出了三对氧化还原峰,是由于Dy与Ni形成了合金化合物,导致Dy(III)离子在活性Ni电极发生了欠电位沉积.采用X射线衍射(XRD)和扫描电子显微镜(SEM)附带能量散射谱(EDS)对恒电位(-1.6,-1.8和-2.0 V)电解制备的Dy-Ni合金进行分析,分别获得了DyNi5, Dy2Ni7和DyNi2金属间化合物.实验结果表明,通过控制电位进行恒电位电解可以有选择性地制备不同的金属间化合物.     

LiCl-KCl熔盐体系中镨(Ⅲ)在镍电极上的电化学行为

采用循环伏安、方波伏安、计时电位和开路计时电位等电化学方法研究了Pr(Ⅲ)离子在共晶LiClKCl熔盐中Ni电极上的电化学行为及Pr-Ni合金化机理.结果表明,Pr(Ⅲ)离子的电化学还原过程为三电子转移的一步反应.与惰性Mo电极上的循环伏安曲线相比,Pr(Ⅲ)离子在活性Ni电极的循环伏安曲线上还出现了4对氧化还原峰,表明Pr(Ⅲ)离子在Ni电极上发生欠电位沉积,是由于生成不同的Pr-Ni金属间化合物.采用X射线衍射仪和扫描电子显微镜-能谱仪等对恒电位电解的产物进行了表征.结果表明,在不同电位下进行恒电位电解时,每个电位上只得到一种Pr-Ni金属间化合物,分别为Pr Ni2,Pr Ni3,Pr2Ni7和Pr Ni5.     

LiCl-KCl熔盐体系中镨(Ⅲ)在镍电极上的电化学行为

采用循环伏安、 方波伏安、 计时电位和开路计时电位等电化学方法研究了Pr(Ⅲ)离子在共晶LiCl-KCl熔盐中Ni电极上的电化学行为及Pr-Ni合金化机理. 结果表明, Pr(Ⅲ)离子的电化学还原过程为三电子转移的一步反应. 与惰性Mo电极上的循环伏安曲线相比, Pr(Ⅲ) 离子在活性Ni电极的循环伏安曲线上还出现了4对氧化还原峰, 表明Pr(Ⅲ)离子在Ni电极上发生欠电位沉积, 是由于生成不同的Pr-Ni金属间化合物. 采用X射线衍射仪和扫描电子显微镜-能谱仪等对恒电位电解的产物进行了表征. 结果表明, 在不同电位下进行恒电位电解时, 每个电位上只得到一种Pr-Ni金属间化合物, 分别为PrNi₂, PrNi₃, Pr₂Ni₇和PrNi₅.     

Dy(Ⅲ)离子在LiCl-KCl熔盐中的电化学行为及Dy-Ni金属间化合物的选择性制备

采用循环伏安、方波伏安和开路计时电位等电化学方法研究了Dy(Ⅲ)离子在LiCl-KCl 共晶盐中的电化学行为及Dy-Ni 合金形成的电化学机理. 循环伏安和方波伏安法研究表明, Dy(Ⅲ)离子的电化学还原过程为三个电子转移的一步反应. 与惰性W电极相比, Dy(Ⅲ) 离子在Ni 电极上的循环伏安曲线多出了三对氧化还原峰,是由于Dy与Ni 形成了合金化合物, 导致Dy(Ⅲ)离子在活性Ni 电极发生了欠电位沉积. 采用X射线衍射(XRD)和扫描电子显微镜(SEM)附带能量散射谱(EDS)对恒电位(-1.6, -1.8 和-2.0 V)电解制备的Dy-Ni 合金进行分析, 分别获得了DyNi₅, Dy₂Ni₇和DyNi₂金属间化合物. 实验结果表明, 通过控制电位进行恒电位电解可以有选择性地制备不同的金属间化合物.     

EQCM analysis of Bi oxidation mechanism on a Pt electrode

The electro-oxidation behaviours of bismuth (Bi) species adsorbed on a platinum (Pt) anode were investigated using an in situ electrochemical quartz crystal microbalance analysis in the measurement of cyclic voltammetry (CV) and electrochemical impedance spectroscopy under potentiostatic mode. In the CV of Bi modified Pt, there were four distinct features in the current–potential curves during an anodic scan: (i) the adsorption of water molecules in acidic media, (ii) the formation of Bi oxide, (iii) ionization of Bi oxide and (iv) partial desorption of Bi species. During a cathodic scan, the Bi modified Pt surface recovered to its original state via the reduction of Bi oxide and re-deposition of Bi ion. Surface mass data with electrical charge change and impedance measurements of Bi modified Pt supported the electrocatalytic oxidation of bismuth species as the responsible mechanism.     

Universal Algorithm for Simulating and Evaluating Cyclic Voltammetry at Macroporous Electrodes by Considering Random Arrays of Microelectrodes

An algorithm for the simulation and evaluation of cyclic voltammetry (CV) at macroporous electrodes such as felts, foams, and layered structures is presented. By considering 1D, 2D, and 3D arrays of electrode sheets, cylindrical microelectrodes, hollow-cylindrical microelectrodes, and hollow-spherical microelectrodes the internal diffusion domains of the macroporous structures are approximated. A universal algorithm providing the time-dependent surface concentrations of the electrochemically active species, required for simulating cyclic voltammetry responses of the individual planar, cylindrical, and spherical microelectrodes, is presented as well. An essential ingredient of the algorithm, which is based on Laplace integral transformation techniques, is the use of a modified Talbot contour for the inverse Laplace transformation. It is demonstrated that first-order homogeneous chemical kinetics preceding and/or following the electrochemical reaction and electrochemically active species with non-equal diffusion coefficients can be included in all diffusion models as well. The proposed theory is supported by experimental data acquired for a reference reaction, the oxidation of [Fe(CN)₆]⁴⁻ at platinum electrodes as well as for a technically relevant reaction, the oxidation of VO₂⁺ at carbon felt electrodes. Based on our calculation strategy, we provide a powerful open source tool for simulating and evaluating CV data implemented into a Python graphical user interface (GUI).     

Functionalized-graphene modified graphite electrode for the selective determination of dopamine in presence of uric acid and ascorbic acid

Graphene is chemically synthesized by solvothermal reduction of colloidal dispersions of graphite oxide. Graphite electrode is modified with functionalized-graphene for electrochemical applications. Electrochemical characterization of functionalized-graphene modified graphite electrode (FGGE) is carried out by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The behavior of FGGE towards ascorbic acid (AA), dopamine (DA) and uric acid (UA) has been investigated by CV, differential pulse voltammetry (DPV) and chronoamperommetry (CA). The FGGE showed excellent catalytic activity towards electrochemical oxidation of AA, DA and UA compared to that of the bare graphite electrode. The electrochemical oxidation signals of AA, DA and UA are well separated into three distinct peaks with peak potential separation of 193mv, 172mv and 264mV between AA-DA, DA-UA and AA-UA respectively in CV studies and the corresponding peak potential separations in DPV mode are 204mv, 141mv and 345mv. The FGGE is successfully used for the simultaneous detection of AA, DA and UA in their ternary mixture and DA in serum and pharmaceutical samples. The excellent electrocatalytic behavior of FGGE may lead to new applications in electrochemical analysis.     

Polystyrene sulphonate wrapped multiwalled carbon nanotubes modified graphite electrode for simultaneous determination of ascorbic acid, dopamine and uric acid

Graphite electrode is modified by casting multi-walled carbon nanotubes (MWCNTs) wrapped with polystyrene sulphonate (PSS) onto the surface of the bare graphite electrode. The modified electrode was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The behavior of the modified electrode towards the oxidation of ascorbic acid (AA), dopamine (DA) and uric acid (UA) has been determined by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry (CA). The modified electrode showed better electrocatalytic activity towards AA, DA and UA compared to bare graphite electrode. The electrochemical oxidation signals of AA, DA and UA are well separated into three distinct peaks with peak potential difference of 222, 128 and 350 mV between AA-DA, DA-UA and AA-UA respectively in CV studies and corresponding peak potential separation in DPV are 228, 120 and 348 mV. This modified electrode was successfully used for simultaneous determination of AA, DA and UA in ternary mixture.     

Electrochemical behavior of tartaric acid at CuGeO3 nanowire modified glassy carbon electrode

The electrochemical behavior of tartaric acid at the CuGeO₃ nanowire modified glassy carbon electrode has been investigated by cyclic voltammetry (CV). The results show that two pairs of semireversible electrochemical peaks are observed and can be assigned to the process of oxidation–reduction and adsorption–desorption of tartaric acid at the modified glassy carbon electrode, respectively. The intensity of the CV peaks increases linearly with the increase of the content of tartaric acid in the range of 0.01–5 mM and scan rate ranging from 25–200 mV s^?1. CuGeO₃ nanowire modified glassy carbon electrode exhibits good detection ability for tartaric acid in neutral solution with the detection limit of 8.9 and 7.7 μM for cvp1 and cvp2, respectively, at a signal-to-noise ratio of 3. The CuGeO₃ nanowire modified glassy carbon electrode has good reproducibility and stability.     

Electrocatalytic Investigations of Cu(II) and Fe(III) Complexes of Salophen Derivative Schiff Bases on the Pencil Graphite Electrode

This present study describes a pencil graphite electrode surface covered with Cu(II) and Fe(III) complexes based on Salophen derivative Schiff bases in acetonitrile solution containing LiClO₄ as a supporting electrolyte. Cyclic voltammetry method was used for the surface modification procedure with 25 cycle at a sweep rate of 50 mV s^?1. Some characterization methods were used to identify of the prepared modified surfaces including cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), Ultraviolet‐visible Spectroscopy (UV‐Vis), and Scanning Electron Microscopy/Energy Dispersive X‐ray Spectroscopy (SEM/SEM‐EDX). The catalytic activity of these modified surfaces on the electrochemical oxidation of catechol (CC) was investigated and they compared with each other. The results demonstrated that these modified electrodes showed perfect electrocatalytic activity on the catechol determination, however the modified electrode prepared with the Cu(II) complex has higher catalytic activity than this prepared with the Fe(III) complex thanks to its the lower detection limit.     

Hydrothermal ammoniated treatment of PAN-graphite felt for vanadium redox flow battery

A novel method of hydrothermal ammoniated treatment on the polyacrylonitrile (PAN)-based graphite felt for vanadium redox flow battery was developed. The graphite felt was treated in a Teflon-lined stainless steel autoclave for different time at 180 °C. The content of nitrogen in the PAN graphite felt changed from 3.803% to 5.367% by adjusting treatment time to 15 h in ammonia solution, while FT-IR results indicated that nitrogenous groups were introduced. The electrochemical properties of these graphite felts were characterized by cyclic voltammetry, electrochemical impedance spectroscopy, as well as cell charge and discharge tests. The energy efficiency of the treated graphite felt reached 85% at a current density of 20 mA/cm². The corresponding coulombic efficiency and voltage efficiency were 95.3% and 75.1%, respectively. The improvement of the electrochemical properties for the treated graphite felt might be attributed to the increase of polar nitrogenous groups of carbon fiber surface, which facilitated charge transfer between electrode and vanadium ions.     

Electrochemical Oxidation of ds‐DNA on Polypyrrole Nanofiber Modified Pencil Graphite Electrode

Preparation of a polypyrrole nanofiber (PPyNF) modified pencil graphite (PG) electrode and its usage in the electrochemical DNA biosensors was investigated. The electrodes (PPyNF/PG1 and PPyNF/PG2) were prepared from a solution containing 0.1 M pyrrole, 0.1 M Na₂CO₃ and 0.1 M LiCIO₄ by using potentiostatic and potentiodynamic methods. PPyNF/PG2 electrodes which were prepared by potentiostatic procedure showed higher responses for the oxidation of ds‐DNA than the PPyNF/PG1 electrodes prepared by potentiodynamic methods. Immobilization of the ds‐DNA on PG and PPyNF/PG surfaces was performed at a constant potential, +0.5 V, for 300 s in 0.5 M ABS (pH 4.8) containing 15 μg mL^?1 ds‐DNA and 20 mM LiCIO₄. The oxidation peak potentials of the ds‐DNA bases, guanine and adenine, were shifted to more cathodic values by using PPyNF/PG electrodes. The oxidation signal of the guanine base of ds‐DNA was decreased in the presence of methylene blue.