金属离子在多孔硅表面和吸附与电镀过程中金属在多孔硅表面的淀积

刚制备的多孔硅与金属盐溶液接触会产生金属离子在多孔硅表面和吸附现象。实验显示这一现象只发生在新鲜的多孔硅表面, 而存放一月以后的样品不具备此性质。文中把这一现象归因于新鲜的多孔硅表面电子的富集, 溶液中金属离子从多孔硅表面获得电子而附着。多孔硅表面电镀金属过程中, 一定电压下电镀电流密度在起始阶段逐渐下降, 可以用一个指数关系式较好地描述, 在本文中有一个唯象模型予以解释。     

金属离子在多孔硅表面和吸附与电镀过程中金属在多孔硅表面的淀积

刚制备的多孔硅与金属盐溶液接触会产生金属离子在多孔硅表面和吸附现象。实验显示这一现象只发生在新鲜的多孔硅表面, 而存放一月以后的样品不具备此性质。文中把这一现象归因于新鲜的多孔硅表面电子的富集, 溶液中金属离子从多孔硅表面获得电子而附着。多孔硅表面电镀金属过程中, 一定电压下电镀电流密度在起始阶段逐渐下降, 可以用一个指数关系式较好地描述, 在本文中有一个唯象模型予以解释。     

The influence of the surface preparation on the electrodeposition of gold particles on silicon

In a systematical study of the electrodeposition of gold (I) on silicon (100), the influence of the surface preparation on the nucleation behavior of gold was investigated. A two-phase experimental design was used. In the first phase, it was investigated whether there is an influence; in the second phase, an optimization was performed. It was found that more homogeneous particle coverages and higher particle densities can be obtained when the surface is dipped in an acid fluoride solution with small nitric acid to hydrogen fluoride proportions. Furthermore, the observations indicated that more negative deposition potentials also lead to better coverages, higher densities, and less clustering.     

Trace determination of iron on a silicon wafer surface by silicon direct bonding and neutron activation analysis

In order to determine iron on silicon wafer surface at a level of 10¹⁴ atoms·m^–2 the efficiency of a well-type Ge detector for⁵⁹Fe -ray emissions was measured and a low temperature silicon direct bonding technique was developed. With silicon direct bonding at a temperature of 350 to 650°C iron remains near the interface of the bound silicon. The iron contamination of the interface escaped from the interface can be ignored with this technique. The value of iron obtained was (2.7 to 5.9)·10¹⁴ atoms · m^–2 in the surface on silicon wafers.     

Exaltation effects in the metal electrodeposition from acid electrolytes

The exaltation of mass transfer of discharging cations, caused by the concurrent hydrogen evolution from acidified solutions, results in a sharp increase in the metal deposition rate. In this case the limiting process rate depends linearly on the hydrogen evolution current density; it depends but weakly on the solution agitation and temperature. Under the electrolysis of solutions containing weak acids as a supporting electrolyte, the higher the acid formation constant, the more pronounced is the dependence of the electrodeposition limiting rate on the hydrogen current density. When microelectrodes are used, the varying of the background acid nature may affect the hydrogen evolution rate markedly, while the metal electrodeposition rate mainly depends on the cell voltage. When metals are electrodeposited from complex anions, the parallel hydrogen evolution hinders the mass transfer; this process depends on the anion stability constant and charge, all other conditions being the same. The found peculiarities can be used in the inversion voltammetry for the lowering of the metal detection limit, improving of the analysis selectivity, and time saving.     

Polyethylene glycol in copper electrodeposition onto a rotating disk electrode

Many of the proprietary additive formulations that have been proposed to control the properties of metal electrodeposits include water soluble macromolecules. Among these are the hydrodynamically interesting polyethylene glycols ‘Polyox’. In the course of a rotating disk electrode study of the effects of additives in copper electrodeposition the present authors had cause to try the effects of low concentrations of Polyox in an acid copper sulphate plating solution. In the presence of an essential trace of chloride ion Polyox very strongly inhibited deposition below a critical overpotential at which current density rises extremely rapidly with increasing overpotential. These results suggest that below the critical overpotential chloride ions hold a film of Polyox onto the electrode surface and may also give the film some lateral cohesion. The film may be a Polyox-cuprous chloride complex. Striking spiral patterns form at the critical overpotential. Their characteristics are explained as the consequences of electrodeposition on a surface containing submicroscopic protrusions and depressions in conditions where current density increases very rapidly with potential.     

Cost-effective electrodeposition of platinum nanoparticles with ionic liquid droplet confined onto electrode surface as micro-media

We report here for the first time on the use of a droplet of water-immiscible ionic liquid (IL) containing metallic precursor confined onto electrode surface as new micro-media for cost-effective electrodeposition of platinum nanoparticles. 1-n-Butyl-3-methylimidazolium hexafluorophosphate (BmimPF₆), a typical water-immiscible IL, is found to be able to form a stable droplet onto electrode surface in which the metallic precursor (i.e., chloroplatinic acid hexahydrate (H₂PtCl₆)) for electrodeposition of Pt nanoparticles can be stably dissolved when the prepared electrode is used in aqueous solutions. The electrodeposition of Pt nanoparticles is carried out in the aqueous solution of 0.1 M KPF₆ with the H₂PtCl₆-containing IL droplet-confined glassy carbon electrode as working electrode at −1.5 V vs. Ag/AgCl. The Pt nanoparticles electrodeposited from the IL droplet micro-medium are characterized to have a uniform morphology and to possess an excellent electrocatalytic activity toward the oxidation of methanol. Compared with the existing methods for the electrodeposition of metals with ILs as the solvents, the method demonstrated here requires a less amount of ILs and metallic precursors and is thus anticipated to provide a new and cost-effective approach to the deposition of metallic nanoparticles onto conducting substrate.     

Effect of hydrodynamic conditions on the silver electrodeposition from water-ethanol solutions of electrolytes

Effect of hydrodynamic conditions on the silver electrodeposition from the aqueous and water-ethanol solutions of silver nitrate is studied with the purpose of the establishing the process limiting step nature. In the investigated systems of the silver electrodeposition in the potentiodynamic regime the current strength depends on the intensity of stirring and is changed due to the change in the limiting step and the surface morphology. Adding of nonaqueous solvent to the larger extent influences the electrolytic rather than diffusion stage of the process.     

The effect of magnetic fields on the electrodeposition of iron

The effect of a uniform magnetic field with flux density up to 1 T on the electrodeposition of Fe from sulphate electrolyte has been investigated under different field configurations relative to the electrode surface. Voltammetric and chronoamperometric experiments have been carried out coupled with an electrochemical quartz crystal microbalance for in situ mass change measurements. The structure and morphology of the deposited films were determined by scanning electron microscopy, atomic force microscopy and X-ray diffraction measurements. Results show that, when the magnetic field is applied parallel to the electrode surface, the limiting current density and the deposition rate are increased due to the magnetohydrodynamic effect. The nucleation process is also affected in parallel configuration; the current density of the maximum on the chronoamperograms is decreased, and an additional nucleation step might be observed. This effect is attributed to the hydrodynamic response of the electrochemical system. No significant influence on the electrochemical reaction was observed when a magnetic field was applied perpendicular to the electrode. But in this configuration, the morphology of deposited layers is changed by the magnetic field. The morphology changes are discussed. No effect of the magnetic field on the crystallographic structure was observed.     

Direct electrodeposition of PbTe thin films on n-type silicon

High quality lead telluride thin films were directly deposited onto n-type silicon (1 0 0) substrates by electrodeposition at room temperature. The deposition mechanism was studied using cyclic voltammetry. The films were characterized by scanning electron microscopy, energy dispersive X-ray, X-ray diffraction, and Fourier transform infrared spectroscopy. The results indicated that the deposited PbTe films exhibited a polycrystalline rock salt structure and good optical properties with a direct band gap of 0.31 eV.     

Fast electrodeposition of zinc onto single zinc nanoparticles

The zinc deposition reaction onto metallic zinc has been investigated at the single particle level through the electrode-particle collision method in neutral solutions, and in respect of its dependence on the applied potential and the ionic strength of a sulphate-containing solution. Depending on the concentration of sulphate ions in solution, different amounts of metallic zinc were deposited on the single Zn nanoparticles. Specifically, insights into the electron transfer kinetics at the single particles were obtained, indicating an electrically early reactant-like transition state, which is consistent with the rate-determining partial de-hydration/de-complexation process. Such information on the reaction kinetics at the nanoscale is of vital importance for the development of more efficient and long-lasting nanostructured Zn-based negative electrodes for Zn-ion battery applications.

     

Selective electrodeposition of ZnO onto Cu2O

The co-deposition of cuprous oxide (Cu₂O) and zinc oxide (ZnO) on indium tin oxide (ITO) substrate was executed by two different electrochemical methods and the formation mechanism of ZnO onto Cu₂O was investigated by ex-situ SEM, XRD, and XPS. The single galvanostatic electrodeposition step in a mixed nitrate electrolyte offered a useful method in preparing ZnO onto triangular Cu₂O islands formed. On the other hand, hexagonal shaped ZnO phase was electrodeposited on ITO substrate as well as on Cu₂O islands when two steps of the galvanostatic and potentiostatic process were applied.     

On the electrodeposition of coherent gadolinium dendrites from molten fluoride electrolytes

The morphology of gadolinium dendrites deposited in molten fluorides may be linked with the stability of electroactive associates. Quantum chemical calculations of moieties, based on the solid state structure of GdF₃, reveal an increased overall stabilizing attraction in the following order: $$Gd_{1 - x} Ba_x F_{3 - x}< GdF_3< Gd_{1 - x} F_{3 - 2x} O_x< Gd_{1 - x} Ca_x F_{3 - x} $$ The stabilization of the 75 LiF-25 mol% GdF₃ electrolyte by oxyfluorocomplexes led to the deposition of essentially pure gadolinium dendrites. The fluorine contamination caused by salt inclusions was consequently reduced from the 1,500–2,000 ppm, as obtained in the pure LiF-GdF₃ electrolyte, to less than 3 ppm.     

Dynamics of copper electrodeposition onto fibrous carbon electrodes

Distribution of copper electrodeposited from a sulfuric acid solution onto fibrous carbon electrodes, copper deposition rate, and current efficiency by the metal were studied in relation to the electrolysis duration, electrical conductivity of the electrode, geometric current density, and solution flow rate. The variation of the electrode thickness on which copper ions discharge at the limiting diffusion current at various solution flow rates and the electrode thickness on which the whole amount of oxygen dissolved in the electrolyte is reduced were calculated in relation to the solution flow rate and geometric current density. The main factors governing the distribution of copper across the electrode thickness and the electrolysis parameters from the beginning of the process till ??clogging?? of a part of the electrode by the metal were determined.     

Sorption and desorption of phenanthrene onto iron, copper, and silicon dioxide nanoparticles

The sorption and desorption of phenanthrene by three engineered nanoparticles including nanosize zerovalent iron (NZVI), copper (NZVC), and silicon dioxide (NSiO2) were investigated. The sorption of phenanthrene onto NSiO2 was linear and reversible due to the hydrophilic properties of NSiO2. In comparison, sorption of phenanthrene onto NZVI and NZVC was nonlinear and irreversible, which was potentially due to the existence of significantly heterogeneous surface energy distribution patterns detected by a standard molecular probe technique. Naphthalene exerted significant competitive sorption with phenanthrene for NZVI and NZVC, and the isotherm of phenanthrene changed from being significantly nonlinear to nearly linear when naphthalene was simultaneously absorbed. A surface adsorption mechanism was proposed to explain the observed sorption and competition of phenanthrene on both NZVI and NZVC. In contrast, no competition was observed for sorption onto NSiO2. The sorption of phenanthrene on all three nanoparticles significantly decreased with increasing pH. The sorption irreversibility of phenanthrene on NZVI and NZVC were significantly enhanced with decreasing pH. A pH-dependent hydrophobic effect and dipole interactions between the charged surface (electron acceptors) and phenanthrene with electron-rich pi systems (electron donors) were proposed to explain the observed pH-dependent sorption.     

缓冲剂对镀镍过程作用机理的研究

缓冲剂对镀镍过程作用机理的研究①高灿柱鹿玉理刘汝涛陈方（山东大学环境工程系济南２５０１００）李树本（中国科学院兰州化学物理研究所兰州７３００００）电镀镍是量大面广的镀种，它作为镀铬、贵金属、仿金、枪黑、黑镍的底层，用途非常广泛［１］．在镀镍过程中，...     

Indirect (hydrogen-driven) electrodeposition of porous silver onto a palladium membrane

Hydrogen permeation through a pure palladium film (25 μm thickness, optically dense) is employed to trigger electron transfer (hydrogen-driven) reactions at the external palladium | aqueous electrolyte interface of a two-compartment electrochemical cell. Two systems are investigated to demonstrate feasibility for (i) indirect hydrogen-mediated silver electrodeposition with externally applied potential and (ii) indirect hydrogen-mediated silver electrodeposition driven by external formic acid decomposition. In both cases, porous metal deposits form as observed by optical and electron microscopies. Processes are self-limited as metal deposition blocks the palladium surface and thereby slows down further hydrogen permeation. The proposed methods could be employed for a wider range of metals, and they could provide an alternative (non-electrochemical or indirect) procedure for metal removal or metal recovery processes or for indirect metal sensing.

Graphical abstract

     

The effect of chemisorbed sulfide ions on the gold electrodeposition from acidic thiocarbamide electrolytes

Introducing sodium sulfide (about 10^?5 M) into acidic thiocarbamide solutions reduces the gold reduction overpotential. The reaction rate passes through a maximum at a potential of 0.1 V. The overpotential depends on the sulfide ion concentration and the time of electrode exposure to solution prior to the beginning of scanning. Transients of potential measured on a renewable gold electrode in thiocarbamide electrolytes containing catalytically active species served as the basis for calculations of the coefficient of trapping of sulfide ions by the growing gold deposit. The kinetics of gold electrodeposition at fixed surface coverages with adsorbed sulfide ions θ is studied. It is shown that at θ = const, the dependence of the reaction rate on the overpotential is described by the Tafel equation. It is shown that with an increase in θ, the effective values of exchange current and transfer coefficient increase from i ₀ ≌ 10^?5 A/cm² and α ≌ 0.25 in pure solutions to α ≌ 0.5 and i ₀ ≌ 10^?4 A/cm² at θ ≥ 0.3 and then remains virtually unchanged. The reaction order decreases in the absolute magnitude, remaining negative. Thus for θ ≌ 0, p _k = ?logi/?logc = ?1, whereas for θ ≥ 0.3, p _k = ?0.3. A possible explanation is proposed for the catalytic effect of the sulfide ion adsorption on the mechanism of the gold reduction from acidic thiocarbamide electrolytes.