Stability of iodine on ruthenium during copper electrodeposition and its effects on the nucleation behavior of electrodeposited copper

Cyclic voltammetry, current-time-transient measurements, and X-ray photoelectron spectroscopy (XPS) have been used to study the nucleation behavior of electrochemically deposited Cu films on Ru substrates as a function of Ru pre-treatment. Pre-treatment consisted of cathodic polarization in either 1 M H₂SO₄ or in 1 M H₂SO₄ + 1 mM KI, followed by sample emersion and placement in a 1 M H₂SO₄ + 50 mM CuSO₄ plating bath. XPS measurements confirmed the presence of adsorbed I on the Ru surface following pre-treatment in the KI/H₂SO₄ solution. Cyclic voltammogram (CV) data for electrodes either as-received or pre-reduced in H₂SO₄ and then immersed in the plating solution exhibited a broad peak in the overpotential region consistent with oxide reduction followed by Cu deposition. No underpotential deposition (UPD) feature was observed for these electrodes. In contrast, the sample pre-reduced in I-containing electrolyte exhibited a narrow Cu deposition peak in the overpotential region and a UPD Cu feature centered at 80 mV vs. Ag/AgCl. Current-time-transient (CTT) measurements of Cu deposition on as-received electrodes or electrodes pre-reduced in I-free solution exhibited potential-independent kinetics that are not well described by either progressive or instantaneous nucleation models and which at long times indicate a combination of diffusion and kinetic control. In contrast, CTT measurements of deposition kinetics for samples reduced in I-containing electrolyte exhibited complex, potential-dependent behavior and that at long times indicates diffusion control. XPS results also indicated that the iodine adlayer on Ru reduced in I-containing electrolyte is stable upon polarization to at least −200 mV vs. Ag/AgCl. These data indicate that a protective I adlayer may be deposited on an air-exposed Ru electrode as the oxide surface is electrochemically reduced, and that this layer will inhibit reformation of an oxide during the Cu electroplating process. Therefore, electrochemical pre-treatment in I-containing electrolyte may be of practical utility under industrial conditions for Cu electroplating.     

Ruthenium selenide catalysts for cathodic oxygen reduction in direct methanol fuel cells

The oxygen reduction reaction in sulphuric acid on commercial carbon supported platinum and ruthenium catalysts as well as on a home-made carbon supported ruthenium selenide catalysts (RuSe _x /C) was investigated. The RuSe _x /C catalysts were synthesised using similar procedures to those found in the literature. A dependency of H₂O₂ formation on the selenium content was found using the thin-film rotating ring disc electrode technique, namely that the H₂O₂ formation in the typical operation range of a Direct Methanol Fuel Cell (0.7–0.4 V) on Pt/C is below 1% and 1–4% on Ru/C and RuSe _x /C catalysts. Finally for comparing the intrinsic activities of the catalysts the electrochemically active surface areas were determined in-situ by means of copper underpotential deposition. Our results indicate a comparable activity of the present RuSe _x /C catalyst to commercial Pt/C if the activities are related to the electrochemical active areas.     

Morphology and composition of the Fe-Ni powders electrodeposited from citrate containing electrolytes

The electrodeposition of the Fe-Ni powders from citrate containing electrolytes for different Ni/Fe ions concentration ratios, using Fe(III) and Fe(II) salts at pH 4.5 and pH 4.0 respectively was investigated by the polarization measurements and cyclic voltammetry. The morphology and composition of the electrodeposited powders were investigated by SEM and EDS analysis. The EDS analysis of the alloy powders confirmed anomalous co-deposition of Fe and Ni from both solutions, with the one obtained using Fe(III) salt being more pronounced. The morphology of electrodeposited powders was found to depend on the Ni/Fe ions concentration ratio, as well as on the valence of Fe ions used. A common characteristic for all powder samples was the presence of cone shaped cavities and nodules, while for the ratio Ni/Fe = 9/1 in both electrolytes pagoda like crystals, corresponding to the FeNi₃ single crystal, have been detected. In the case of Fe(III) containing electrolytes current efficiency for powder electrodeposition was very small (about 1-2%) due to the first step in the electrochemical reaction being reduction of Fe(III) into Fe(II), while in the case of Fe(II) containing electrolytes current efficiency for powder electrodeposition varied between about 15% and 8% depending on the Ni/Fe ratio.     

Electrochemical study on the inhibitory effect of the underpotential deposition of zinc on Zn-Co alloy electrodeposition

Zn-Co alloy electrodeposition from chloride baths containing different Zn²⁺/Co²⁺ ratios was investigated by cyclic voltammetry and anodic linear sweep voltammetry using a Pt electrode. The peaks were attributed by means of EDX analysis, SEM and TEM observations performed on some alloys potentiostatically deposited. In the range of potential where zinc deposits underpotential, cyclic voltammetry showed a complex cathodic peak with one maximum and two shoulders, correlated with the deposition of different cobalt rich alloys. Up to four anodic peaks, two correlated with zinc oxidation from η and γ phases and two correlated with oxidation of solid solutions of zinc in cobalt, were observed. ALSV and TEM indicated that the remarkable increase in Zn content of the alloy, which occurs with a strong inhibition of the process at potentials more negative than that of the cathodic peak and more positive than the bulk deposition potential of zinc, is due to the deposition of γ phase. No inhibition of the alloy deposition process was observed with very low concentrations of zinc (<0.015 M) in the bath containing 0.19 M Co²⁺.     

Ruthenium electrodeposition on silicon from a room-temperature ionic liquid

Electrochemical deposition of ruthenium on n-type silicon from an ionic liquid is reported for the first time. The study was performed by dissolving ruthenium(III) chloride in a 1-butyl-3-methyl imidazolium hexafluorophosphate (BMIPF₆) room-temperature ionic liquid (RTIL). Cyclic voltammetry (CV) studies demonstrate reduction and stripping peaks at −2.1 and 0.2 V vs. Pt quasi-reference, corresponding to the deposition and dissolution of ruthenium, respectively. Metallic Ru films of ∼100 nm thickness have been deposited and were analyzed using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS).     

Electrodeposition of copper on Ru(0 0 0 1) in sulfuric acid solution: Growth kinetics and nucleation behavior

The electrodeposition of Cu on Ru(0 0 0 1) from 0.1 M CuSO₄/0.5 M H₂SO₄ solution has been studied by cyclic voltammetry, current-time transient measurements, and by in situ electrochemical atomic force microscopy (EC-AFM). Cyclic voltammetry measurements show that the as-prepared Ru(0 0 0 1) electrode exhibits a UPD peak, while EC-AFM data indicate a broadly terraced surface with step heights of atomic dimensions. Kinetic data show that the electrodeposition/nucleation process is not well described by 3D or 2D nucleation models. The EC-AFM data show that at potentials near the OPD/UPD threshold, Cu crystallites exhibit pronounced growth anisotropy, with lateral dimensions greatly exceeding vertical dimensions. AFM data also show that deposition at more cathodic potentials result in smaller crystallites.     

Magnetic properties of nanocrystalline iron group thin film alloys electrodeposited from sulfate and chloride baths

Systematic studies of iron group binary (NiCo and CoFe) and ternary (CoNiFe) thin film alloys relating their magnetic properties with film composition, grain size and the corresponding crystal structure were investigated. Anions influence current efficiencies, magnetic properties, surface morphology and phases of electrodeposited films. Higher current efficiencies in chloride baths compared to sulfate baths were observed for CoFe, NiCo and CoNiFe alloys. The higher deposition current efficiencies in chloride baths were attributed to a catalytic effect. Anion types in CoFe and CoNiFe thin film alloys influenced the microstructures and the resulting magnetic properties (coercivity and squareness). The microstructures of NiCo alloys depend on the deposit Co contents rather than anion types. The surface morphologies of CoFe, NiCo and CoNiFe thin films were independent of anion types. CoFe deposits exhibited relatively smooth surface morphology and turned into fine crystallites with increasing solution Fe⁺² concentration. NiCo deposits showed very smooth surface morphology. CoNiFe deposits had the surface morphology of polyhedral crystallites. The deposit Fe content in CoFe electrodeposits linearly increased with increasing solution Fe⁺² concentration for both chloride and sulfate baths. Similar linear behavior of deposit Co contents was observed in NiCo electrodeposits.     

The kinetics of copper island growth on ruthenium oxide in perchlorate solution

The nucleation potential for the deposition of copper on ruthenium oxide is very small and hence island growth can occur in the kinetic regime. Previously, we have reported on island growth in sulfate solution where anion adsorption results in the formation of hexagonal, disk-shaped islands. Here we report on island growth in perchlorate solution, in the absence of specific anion adsorption. All islands have a 〈1 1 1〉 surface orientation dictated by the amorphous substrate. The islands are hemispherical in shape and island growth follows power law kinetics in both lateral and vertical directions with exponents 0.50 and 0.26, respectively. From analysis of the time-dependent extended area using Avrami analysis, analysis of the near-neighbor distribution, and the correlation between the island size and the spatial distribution, we conclude that island growth is controlled by surface diffusion-mediated lateral growth.     

Electrochemical deposition of copper and ruthenium on titanium

Copper electrochemical deposition on titanium with a ruthenium seed layer was investigated. The chemicals for the acid-bath ruthenium electrochemical deposition were ruthenium(III) chloride hydrate (RuCl₃·3H₂O), hydrochloric acid (HCl), sulfamic acid (NH₂SO₃H), and polyethylene glycol. The chemicals for the acid-bath copper electrochemical depositions were copper(II) sulfate hydrate (CuSO₄·5H₂O), sulfuric acid (H₂SO₄), and polyethylene glycol. Results were analyzed by field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Rutherford backscattering spectrometry (RBS). Ruthenium thin film of ∼30 nm thickness, with equiaxial grains <10 nm, was deposited, on a blanket Ti with a root mean square roughness of 8.3 nm, at 2 V for 90 s. XPS and RBS analyses showed the presence of metallic Ru. The Ti substrate was found stable with respect to ECD of Ru but the Ru/Ti bilayer was not found stable in the Cu acid bath, resulting in the diffusion of Ti into Ru film. The depth profiling studies indicates that Ru film thickness ca. 1.4 nm and deposition time of 10 s can act as a good seed layer.     

Electrodeposition of mesoscopic Pt-Ru on reticulated vitreous carbon from reverse emulsions and microemulsions: Application to methanol electro-oxidation

High surface area Pt-Ru (between 120 and 400 cm² mg⁻¹) meso-sized particles and mesoporous coatings were electrodeposited on reticulated vitreous carbon (RVC) three-dimensional electrodes using reverse emulsions and microemulsions. The organic phase of the colloidal media was composed of cyclohexane, Triton X-100 non-ionic surfactant and tetrabutylammonium perchlorate (for ionic conductivity) while the aqueous phase contained H₂PtCl₆ and RuCl₃ (or (NH₄)₂RuCl₆). For microemulsification to occur isopropanol was also added as co-surfactant. The catalytic activity for the electro-oxidation of methanol was assessed by cyclic voltammetry and chronopotentiometry in conjunction with surface area measurement by Cu underpotential deposition. The composition and morphology of the Pt-Ru deposit was analyzed by inductively coupled plasma atomic emission spectroscopy and scanning electron microscopy, respectively. The effects on the catalytic activity of the deposition current density, temperature, RVC pretreatment and plating bath composition are presented. It was found that the electrodeposition of Pt-Ru in reverse microemulsion yielded the highest specific surface area (400 cm² mg⁻¹) and catalytic activity toward CH₃OH electro-oxidation as shown, for example, by a 50-200 mV more negative anode potential determined by chronopotentiometry compared to a catalyst obtained by pure aqueous and emulsion electroplating.     

Effect of chloride ions on immersion plating of copper onto porous silicon from a methanol solution

The effect of chloride ions (Cl⁻) during the immersion plating of copper onto porous silicon (PS) from a methanol (MeOH) solution has been studied. The presence of Cl⁻ in the Cu²⁺ solution was found to slow down the rate of copper deposition, as confirmed by inductively coupled argon plasma emission spectroscopy and X-ray photoelectron spectroscopy measurements. The threshold concentration of Cl⁻ at which the deposition of copper is very severely diminished was found to be 0.1 M. The inhibition effect is discussed on the basis of the rest potential values of PS and polarization curve measurements. They revealed that the rest potential of PS upon dipping in these solutions appears to direct the metal deposition. Current density-potential curves show that at Cl⁻ concentrations higher than 0.1 M, the reduction of Cu ions proceeds in two steps; the reduction of Cu(II) to Cu(I) followed by the reduction of Cu(I) to Cu(0). This suggests that Cu(I) species in MeOH solution can be stable over a certain potential range and this stability of Cu(I) is responsible for the inhibition of metal deposition. Fourier transform infrared spectroscopy and scanning electron microscopy (SEM) were also performed to investigate the structural changes and characterizations of PS samples after the plating process.     

Gel polymer electrolytes based on PMMA : III. PMMA gels containing cadmium

Gel polymer electrolyte containing cadmium perchlorate was prepared by polymerisation of methylmethacrylate with a solution containing Cd perchlorate in propylene carbonate (PC). Electric conductivity, fundamental electrochemical properties and Cd electrodeposition were investigated. The deposition of Cd was fairly homogenous.     

Influence of the substrate's surface structure on the mechanism and kinetics of the electrochemical UPD formation of a copper monolayer on gold

The copper electrodeposition process was studied onto different gold substrates, single crystal (1 1 1) and polycrystalline, using electrochemical techniques. It was found, from the analysis of the experimental current density transients, that the potentiostatic formation of a full copper monolayer onto the gold electrode under UPD conditions follows the same mechanism, regardless of the crystallinity of the substrate. The mechanism involved the simultaneous presence of an adsorption process and of two 2D nucleation processes, progressive and instantaneous, respectively.     

Influence of ammonium salt on electrowinning of copper from ammoniacal alkaline solutions

In order to develop an energy-saving copper recycling process from wastes, electrochemical measurements were conducted in ammoniacal alkaline solutions containing Cu(I) ions and an ammonium salt of sulfate, chloride or nitrate. The results of each system were then compared. The polarization measurements suggested that the voltage required for the electrode process is lower in the chloride and nitrate systems than that in the sulfate system. The cathode current efficiency during the copper electrodeposition varied from 39 to 97% and increased with current density in the chloride and sulfate systems. In the nitrate system, the lowest cathode current efficiency of 30% was observed because of nitrate ion reduction. Based on these results, the power consumption required for the electrowinning stage of the copper recycling process was calculated. Among these three systems, the chloride system showed the lowest power consumption of 500 kWh t⁻¹ at the current density of 200 A m⁻², which is about 25% of the conventional copper electrowinning process from a copper sulfate-sulfuric acid solution.     

Reactions of methylcyclopentane on Rh–Pt catalyst prepared by underpotential deposition of Rh on Pt/SiO2

Rh was deposited on to a well-characterized 3.1% Pt/SiO₂ (InCat-1) parent catalyst by underpotential deposition method to obtain a model Rh–Pt bimetallic catalyst. TEM and EDS was used to determine its mean particle size and bulk composition: the particles of ca. 3 nm contained ca. 60% Pt and 40% Rh. The Rh–Pt catalyst was tested in methylcyclopentane (MCP) reaction between 513 K and 603 K and 60–480 Torr H₂ pressure (with 10 Torr MCP). The parent Pt/SiO₂ as well as a 5% Rh/SiO₂ catalyst were also studied for comparison. Four subsequent treatments with O₂ and H₂ up to T = 673 K were applied on the bimetallic catalyst before the catalytic runs. The overall activity showed positive hydrogen order on all samples, bimetallic Rh–Pt resulting in the lowest TOF values. Ring opening and hydrogenolysis products, as well as unsaturated hydrocarbons were formed from MCP. The selectivity of ring opening products and fragments over Rh–Pt catalyst was between the values observed on Pt and Rh, while the selectivity towards benzene formation was highest on the bimetallic sample, especially at higher temperatures. “Selective” ring opening occurred on all samples, resulting mostly in 2 and 3-methylpentane and less hexane. Different pretreatments with H₂ and O₂ affected slightly the dispersion values and the catalytic behavior of Rh–Pt sample. The selectivities of the Rh–Pt catalyst being between the values observed for Pt/SiO₂ and Rh/SiO₂ indicates that the sample studied represented a real bimetallic catalyst, resembling both components and exhibiting at the same time, new properties in addition to those, characteristic of Pt or Rh. Dedicated to Konrad Hayek.     

Effect of heat treatment on stability of gold particle modified carbon supported Pt-Ru anode catalysts for a direct methanol fuel cell

Carbon supported Au-PtRu (Au-PtRu/C) catalysts were prepared as the anodic catalysts for the direct methanol fuel cell (DMFC). The procedure involved simple deposition of Au particles on a commercial Pt-Ru/C catalyst, followed by heat treatment of the resultant composite catalyst at 125, 175 and 200 °C in a N₂ atmosphere. High-resolution transmission electron microscopy (HR-TEM) measurements indicated that the Au nanoparticles were attached to the surface of the Pt-Ru nanoparticles. We found that the electrocatalytic activity and stability of the Au-PtRu/C catalysts for methanol oxidation is better than that of the PtRu/C catalyst. An enhanced stability of the electrocatalyst is observed and attributable to the promotion of CO oxidation by the Au nanoparticles adsorbed onto the Pt-Ru particles, by weakening the adsorption of CO, which can strongly adsorb to and poison Pt catalyst. XPS results show that Au-PtRu/C catalysts with heat treatment lead to surface segregation of Pt metal and an increase in the oxidation state of Ru, which militates against the dissolution of Ru. We additionally find that Au-PtRu/C catalysts heat-treated at 175 °C exhibit the highest electrocatalytic stability among the catalysts prepared by heat treatment: this observation is explained as due to the attainment of the highest relative concentration of gold and the highest oxidation state of Ru oxides for the catalyst pretreated at this temperature.     

Voltammetric study of the influence of benzotriazole on copper deposition from a sulphuric plating bath

Copper electrodeposition on to a platinum substrate from an acid sulphate plating bath was investigated with and without the additive benzotriazole (BTAH). In voltammetric experiments, the deposition process is shifted to more negative potentials in the presence of BTAH than in its absence from the bath. Moreover, the current density of the deposition process was higher in the presence of this additive than in its absence. With or without the additive, copper deposition showed features of nucleation in the voltammetric curves. Scanning electronic microscopy (SEM) images showed that copper deposits laid down in the presence of BTAH, for any potential and charge density studied, were smoother than in the absence of this additive. X-ray spectra indicated that the electrodeposits produced in the absence or presence of BTAH were composed of a mixture of copper, copper oxide and platinum oxide and also indicated that in the presence of BTAH, the deposit was less crystalline than in its absence.     

合成温度对VPO催化剂比表面的影响

在不同的温度下制备VPO催化剂,采用BET、XRD和SEM等测试手段考察制备温度对催化剂的比表面及晶相结构的影响。实验结果表明,温度对比表面和晶相结构的影响存在一个最佳值。选择适宜的制备温度可以使催化剂晶粒变小,比表面增大,活性相含量增加。     

Enantiospecific electrodeposition of chiral CuO films on Cu(1 1 0) from aqueous Cu(II) tartrate and amino acid complexes

CuO films were anodically electrodeposited onto Cu(1 1 0) single crystals from alkaline solutions of Cu(II) complexed with tartrate, alanine, valine, and glycine. In all cases the films were epitaxial, exhibiting varying amounts of the chiral orientations (1 1 0) and (). The enantiomeric excess (ee) of the chiral electrodeposition process was determined by X-ray pole figure analysis. The CuO films deposited from d-tartrate solution exhibited a (1 1 0) out-of-plane orientation with an ee of 61%, while films grown from l-tartrate exhibited a () orientation with an ee of 77%. The CuO film deposited from achiral meso-tartrate had essentially equal amounts of both chiral orientations. Epitaxial CuO films deposited from d-alanine and d-valine both gave () orientation with ee's of 40 and 65%, respectively, while CuO films deposited from l-alanine and l-valine gave (1 1 0) orientations with ee's of 39 and 67%, respectively. Films obtained from a glycine solution showed roughly equal amounts of both chiral orientations.     

乙炔法合成氯乙烯用氯化汞催化剂的改良

简单介绍了乙炔法合成氯乙烯的反应原理、工艺流程、操作条件和主要技术指标,以及氯化汞催化剂的规格和制备方法,讨论了氯化汞催化剂的缺陷,总结了在减少汞流失方面对氯化汞催化剂进行改良的进展情况。