多孔金属连续电沉积数学模型

采用电沉积方法制备连续多孔金属,通过把电流密度随时间的变化转换为镀区内的位置分布,建立了稳恒状态下高孔率带状多孔金属连续电沉积动态模型,推导出表观电流密度分布的数学表达式.并在多孔金属镍实际制备过程中对模型进行了验证,结果表明带状多孔金属与阳极配置满足一定角度时,实现阴极表观电流密度恒定,镍的结晶细致.这一工作为电沉积法制备多孔金属的在线控制提供了理论依据.     

基于电沉积多孔碳修饰电极测定6-苄氨基嘌呤的研究

利用恒电位法沉积多孔碳固定于玻碳电极表面,构建多孔碳修饰电极,利用线性扫描伏安法和差分脉冲伏安法研究了标题化合物在多孔碳修饰电极上的电化学行为,建立了一种测定标题化合物的电化学分析方法。结果表明,与玻碳电极相比,多孔碳修饰电极能显著提高标题化合物的氧化峰电流。在优化的实验条件下,标题化合物的氧化峰电流与浓度在1. 0×10-7~4. 0×10-5mol/L范围内呈较好的线性关系,最低检出限为7. 6×10-8mol/L。本法用于黄豆芽中标题化合物的测定,效果良好。     

电沉积制备多孔铅电极及其对CO2的电还原性能

采用铜片为基底,利用其自身析出的氢气泡为模板,通过电沉积的方法合成了具有三维多孔结构的铅沉积层,并将其作为电极材料应用到CO2的电还原反应中.考察了不同沉积时间及不同沉积电流密度对电极形貌及电催化还原CO2性能的影响,得出在5℃下,沉积电流密度为-6 A/cm2,沉积时间为20 s时,电极催化效果最好,在施加电位为-1.7V时生成甲酸的最高电流效率可达96.8％.     

流通型碳纤维电极的电沉积行为

研究了电极构型对流通型碳纤维电极从ＡｕＣｌ－４稀溶液中电沉积金行为的影响．在顺流操作方式下，整个电极能够在极限电流条件下工作，利用电沉积分布曲线计算了传质系数与流速的关系式．逆流方式可以使电沉积分布更为均匀，从而提高整个电极的利用效率．利用数学模型对各种实验曲线进行了模拟，计算结果与实验结果相符．     

喷射电沉积块体多孔镍的研究

采用喷射电沉积方法制备块体多孔镍.分别选择不同的扫描方式、电流密度进行试验,分析了各试验参数对块体多孔镍形貌的影响规律,并应用图形处理软件ImageJ对多孔镍的孔隙率和相对密度进行分析,获得最佳试验参数.结果表明:采用扫描速率中间部位慢于边界部位、在块体各点均暂停的扫描方式,有利于多孔镍沉积均匀平整.随着电流密度的增加,镍沉积层明显变得致密,孔径减小,而孔隙率增大.     

扫描喷射电沉积制备多孔金属镍

采用扫描喷射电沉积制备具有一定厚度、孔隙率较高、组织较均匀的多孔金属镍;并研究了在不同扫描速率、喷嘴高度等实验条件下,多孔金属镍电沉积生长的行为特性;最后应用图形处理软件Image J对多孔金属镍的孔隙率和相对密度进行分析,得到了最佳实验参数.结果表明:采用扫描速率为4 mm/s时,孔隙结构相当完善;当喷嘴高度为6 mm时,孔隙率和相对密度比较适中.     

电沉积制备多孔Ni-Fe-Sn合金电极及其析氧性能

采用直流电沉积法在铜箔表面合成了多孔结构的Ni–Fe–Sn合金,用扫描电子显微镜、X射线能谱仪和X射线衍射仪对合金的微观组织形貌和相态进行了表征,用电化学工作站测试了合金电极在碱性环境中的析氧性能。结果表明,Ni–Fe–Sn合金电极主要由Ni3Sn2和FeNi3相组成,电极表面形成了多孔结构。在30wt% KOH溶液中,Ni–Fe–Sn合金的析氧过电位仅为261 mV(电流密度10 mA/cm2),Tafel斜率为69.9 mV/dec。电极在10 mA/cm2电流密度下能稳定工作12 h以上,具有良好的电化学稳定性。     

电流密度对电沉积锰结构及性能的影响

锰被广泛应用于钢材中,研究制备高质量的金属锰具有很重要的现实意义。采用石墨阳极,无硒硫氨酸盐电解液,在不锈钢表面电沉积金属锰,采用恒电流法研究了电流密度对电流效率以及镀层厚度的影响。利用X-射线衍射仪测试镀层结构,扫描电镜观察镀层表面形貌,维氏硬度计测试镀层硬度。结果表明,Jκ为14A/dm2时η达到57.63%,镀层δ为37.07μm,硬度为509.53HV,获得表面形貌和晶体结构较优的金属锰。     

电沉积铂研究Ⅰ--工艺条件与镀层性能

研制了2种新的电沉积铂镀液体系：新槽液Ⅰ号和Ⅱ号。通过实验研究了电流密度、温度和主盐含量对镀液电流效率的影响,并与常用的碱性P盐槽液、酸性P盐槽液和DNS槽液进行对比。结果发现：新槽液Ⅰ号在电流密度为2A／dm^2、工作温度为30～40℃以及主盐含量为4～10g/L时,电流效率较高,从而可以在较低的温度下实现光亮镀铂。分散能力实验表明,新槽液Ⅰ号具有良好的分散能力。扫描电镜(SEM)图和X射线晶体衍射(XRD)图也证明,与传统的可获得色泽最白、性能最优的镀层的DNS槽液相比,新槽液Ⅰ号获得的镀层对晶面的择优程度与DNS槽液相近,但其内应力更小、表面更平整、结晶更细致、厚度更大。     

喷射速度对喷射电沉积多孔金属镍的影响

借助电化学技术,采用喷射电沉积的方法,直接制备出具有一定厚度、孔隙率较高、组织较均匀的多孔金属镍,并研究了不同喷射速度对喷射电沉积直接制备多孔金属镍的表面形貌和结构特征的影响。研究结果表明,多孔金属镍的孔隙率随喷射速度的增加先减小后增加。     

Modeling of the impedance response of porous metal hydride electrodes

Porous metal hydride electrodes of the alloy MmNi_3.5-3.7Co_0.7-0.8 Mn_0.3-0.4Al_0.3-0.4 have been characterized by means of impedance spectroscopy. A mathematical model for the impedance response, including effects of diffusion of hydrogen, surface kinetics, conductivity in the metal phase and the solution phase, as well as a continuous, lognormal, particle size distribution, was implemented and fitted to the experimental results by application of a least square fitting routine. The model is based on physical parameters, thus avoiding problems related to the conventional interpretation of impedance spectra in terms of equivalent circuits. Very good agreement between experimental results and model results was obtained for a wide range of frequencies, indicating that physical parameters to a great extent can be determined under realistic operating conditions. The latter was confirmed by independent measurements of the variation in open circuit voltage with respect to the state of charge of the electrode. The model provides an improved methodology for the determination of diffusion coefficients based on electrochemical impedance data. Furthermore, the model can be applied for parametric studies of metal hydride electrodes.     

Modeling on lithium insertion of porous carbon electrodes

MCMBs with different crystal structure were tested for an anode of lithium ion batteries (LIB) and the model describing the behavior of porous anodes was simulated numerically by using orthogonal collocation method (OCM). Kinetic parameters such as diffusion coefficients, exchange current densities, and transfer coefficient, describing electrochemical intercalation system of lithium ions, were estimated by fitting the experimental cyclic voltametry (CV) results with the theoretical ones. It was investigated that the theoretical cyclic voltamograms obtained using above parameters fitted well with the experimental curves for the various scan rates from 1 mV s⁻¹ to 5 μV s⁻¹. The parameters were then evaluated on their extended application in various C-rate-charge/discharge cycling tests with showing good agreements between experiments and simulations. As the results show, it was found that numerical simulations based on both potentiometry and galvanometry experimental data resulted in more accurate parameters of electrochemical system. Simulations indicate there exist the optimum design conditions of electrode and separator to obtain the good performance of lithium ion batteries.     

Copper electrodeposition on pyrolytic graphite electrodes: Effect of the copper salt on the electrodeposition process

The electrodeposition of copper on pyrolytic graphite from CuSO₄ or Cu(NO₃)₂ in a 1.8 M H₂SO₄ aqueous solution was investigated. The Cu deposits were formed potentiostatically and characterized by electrochemical methods, scanning electron microscopy, energy dispersive X-ray and X-ray photoelectron spectroscopy. It was found that the deposition of copper in the presence of CuSO₄ induced the codeposition of sulfate anions. In addition, electrochemical quartz crystal microbalance revealed that the increase of the Cu mass was higher than expected from Faraday's law with the CuSO₄/H₂SO₄ solution. These results confirmed the specific adsorption of anions during the Cu deposition. On the other hand, the use of Cu(NO₃)₂ resulted in a non-contaminated surface with different surface morphologies. The Cu nuclei size, the population density and the surface coverage were monitored as a function of the deposition potential. From the analysis of the chronoamperometric curves, the nucleation kinetics was studied by using various theoretical models. Independently of the Cu source, the nucleation mechanism follows a three-dimensional (3D) process. Copper nucleates according to an instantaneous mode when the deposition potential is more negative than −300 mV versus Ag/AgCl, while the nucleation was interpreted in terms of a progressive mode at −150 mV. The nuclei population densities were also determined by using two common fitting models for 3D nucleation and growth (Scharifker-Mostany and Mirkin-Nilov-Heerman-Tarallo). Their values are reported here as a function of the deposition potential.     

Electrochemical properties of porous bismuth electrodes

The properties of Bi surfaces with different roughnesses were characterized by electron microscopy, cyclic voltammetry, and impedance spectroscopy. Two different strategies were used for preparation of porous bismuth layers onto Bi microelectrode surface in aqueous 0.1 M LiClO₄ solution. Firstly, treatment at potential E < −2 V (vs. Ag|AgCl in sat. KCl) has been applied, resulting in bismuth hydride formation and decomposition into Bi nanoparticles which deposit at the electrode surface. Secondly, porous Bi layer was prepared by anodic dissolution (E = 1 V) of bismuth electrode followed by fast electroreduction of formed Bi³⁺ ions at cathodic potentials E = −2 V. The nanostructured porous bismuth electrode, with surface roughness factor up to 220, has negligible frequency dispersion of capacitance and higher hydrogen evolution overvoltage than observed for smooth Bi electrodes.     

The electrochemical generation of ferrate at porous magnetite electrode

In this work, ferrate(VI) was generated by the electrochemical oxidation of porous magnetite electrodes, made by melting pure magnetite grains. Pretreatment of the anode by cathodic polarization was necessary for ferrate(VI) generation and the achievement of high current efficiency. A electrolyte composition was found to be 16 M NaOH. In this electrolyte, the effect of anode current density J on Fe(VI) synthesis rate, current efficiency, and internal cell temperature were studied. An optimum result was obtained at J=3.3 mA cm⁻², 30 °C in 16 M NaOH for 5 h.     

Role of Mo<Superscript>6+</Superscript> during nickel electrodeposition from sulfate solutions

The effect of Mo⁶⁺ on the current efficiency, deposit quality, surface morphology, crystallographic orientations and polarisation behaviour of the cathode during electrodeposition of nickel from sulfate solutions was investigated. Mo⁶⁺ did not have a significant effect on current efficiency over the concentration range 2–100 mg dm⁻³. However; a decrease in current efficiency by a magnitude of more than 20% was seen at 500 mg dm⁻³. The quality of the nickel deposit with reference to the visual appearance and contamination level varied with varying concentration of Mo⁶⁺; this was also reflected in the morphology and crystallographic orientations of the deposits. Addition of Mo⁶⁺ to the electrolyte introduced two new crystal planes i.e., (220) and (311). Depolarisation of the cathode was noted at lower concentrations of Mo⁶⁺ (2–40 mg dm⁻³) whereas polarisation of the cathode was observed at Mo⁶⁺ concentration >40 mg dm⁻³ .The effect of Mo⁶⁺ on parameters such as Tafel slope (b), transfer coefficient (α) and exchange current density (i ₀) were also determined.     

Fabrication of porous Cu supported Ni-P/CeO2 composite coatings for enhanced hydrogen evolution reaction in alkaline solution

Cost-effective electrodes with high activity for hydrogen evolution reaction (HER) and durability are required to develop clean and renewable hydrogen energy. In this work, a porous Cu supported Ni-P/CeO₂ composite coating was fabricated by a facile electrodeposition technique. Owing to the contribution from the 3D porous Cu support and the incorporating agglomeration-free and uniformly distributed CeO₂ particles into the Ni-P matrix, the optimal composite coating (porous Cu supported Ni-P/CeO₂ (20 g L^-1)) exhibits outstanding electrocatalytic performance with small overpotentials (η) of 118 and 320 mV at a cathodic current density of 10 and 100 mA cm². Moreover, the composite electrode also presents excellent electrochemical stability in the alkaline solution. This work provides a feasible option to fabricate composite electrodes that may have desirable electrochemical properties for HER.     

Improving electrochemical performance of NiO films by electrodeposition on foam nickel substrates

NiO films for lithium-ion batteries were deposited on copper plates and foam nickel substrates by electrodeposition and subsequent heat treatment at 300 °C. At a discharge/charge rate of 0.1 C, foam NiO films delivered reversible capacity larger than 650 mAh g⁻¹ and capacity retention over 93% after 50 cycles. NiO films deposited on foam nickel exhibited higher reversible capacity, better cyclability, as well as higher rate capability than those on copper plates. The unique three-dimensionally porous morphologies of foam NiO films were responsible for the better electrochemical performance, which provided not only high electrode/electrolyte contact area but also a good electronic conduction matrix. The present finding offers a new pathway for the large scale fabrication of high-energy-density electrodes for lithium-ion batteries.     

Cyclic voltammetry study of electrodeposition of Cu(In,Ga)Se2 thin films

The electrodeposition of Cu(In,Ga)Se₂ has been investigated by cyclic voltammetry (CV) in a DMF-aqueous solution that contained citrate as a complexing agent. The effects of the citrate ion on the reduction potentials of Cu²⁺, In³⁺, Ga³⁺ and H₂SeO₃ were examined for a unitary system. Furthermore, a cyclic voltammetry study was performed in a ternary Cu-In-Se system, a quaternary Cu-In-Ga-Se system, and binary Cu-Se, In-Se and Ga-Se systems. The insertion of In and Ga into the solid phase may proceed by an underpotential deposition mechanism, which involves two different routes: In³⁺ and Ga³⁺ reduction by a surface-induced effect from Cu₃Se₂ and/or reaction with H₂Se.     

Direct electrodeposition of metal nanowires on electrode surface

A method for decorating the surface of disk electrodes with metal nanowires is presented. Cu and Ni nanowires with diameters from 1.0 μm to 0.2 μm are directly deposited on the electrode surface using a polycarbonate membrane filter template maintained in contact with the metal substrate by the soft homogeneous pressure of a sponge soaked with electrolyte. The morphologic and structural properties of the deposit are characterized by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The latter shows that the head of nanowires with diameter of 0.4 μm is ordinarily polycrystalline, and that of nanowires with diameter of 0.2 μm is almost always monocrystalline for Cu and frequently also for Ni. Cyclic voltammetries and impedance investigations recorded in alkaline solutions at representative Ni electrodes decorated with nanowires provide consistent values of roughness factor, in the range 20–25.