Electrochemical Deposition Of Silver Research Articles

Isotope effects in the electrodeposition of Ag and Pd

The influence of solvent and its isotope in electrochemical deposition of silver and palladium on pencil graphite from H2O, D2O and MeCN was examined via cyclic voltammetry, chronoamperometry and SEM imaging. The evaluation of the nucleation process was done by comparing the current transients to Scharifker–Hills model of nucleation and the process for all samples was deemed to be progressive and mostly under diffusion control. Kinetic parameters were extracted from I/t curves by curve fitting to Heerman–Tarallo model and it was found that for silver and palladium electrodeposition the isotope of the solvent has a noticeable effect on nucleation rate constant with only a limited effect on the number density of nucleation sites.

Electrochemical Deposition of Silver on Aluminum Alloys

Electrochemical Deposition of Silver on Aluminum Alloys

Electrochemical deposition of silver and copper from a deep eutectic solvent studied using time-resolved neutron reflectivity

Here, we describe new developments in the study of electrodeposition processes with time-resolved dynamic neutron reflectivity (NR) methods to achieve insights into the differences between growth of metal films using a range of electrochemical control functions. We show that the temporal resolution has increased from 1 to 2 h per data set (in our previous studies) to approximately 8 min. We have studied the electrochemical deposition of copper and silver as thin-film metals onto a gold electrode substrate from a deep eutectic solvent using potentiodynamic (PD), potentiostatic (PS) and galvanostatic (GS) electrochemical control functions. In particular, we have utilised novel developments in neutron reflectivity methods to acquire real-time data for the growing metal films. Event mode capture of neutron scattering events, as a function of momentum transfer vector, Q, during electrochemical growth has enabled time-resolved measurement of the neutron reflectivity, R(Q), profiles of the growing metal films. Subsequent fitting and iterative optimisation of the R(Q,t) data reveals the thickness, roughness and relative density (spatially resolved solvent content) of the metal film during growth. These data show that the different electrochemical growth methodologies exhibit different trends in thickness, roughness and solvation. Silver films show an increasing roughness trend with time but these trends are largely independent of growth method. In contrast, the roughness of copper films, grown under similar conditions, shows a strong dependency on growth method with PS methods producing smoothest films. These conclusions are confirmed by ex-situ AFM measurements. The fitted NR data show that the Cu and Ag films contain between 5 and 10% volume fraction solvent. Furthermore, we have explored different NR data fitting methodologies in order to process the large numbers of data sets produced. Gratifyingly, the different methodologies and starting conditions yield a very consistent picture of metal film growth.

Electrochemical deposition of silver on manganese dioxide coated reduced graphene oxide for enhanced oxygen reduction reaction

We have prepared a reduced graphene oxide (rGO)-supported silver (Ag) and manganese dioxide (MnO2) deposited porous-like catalyst (denoted as rGO/MnO2/Ag) through a facile electrochemical deposition route and have been used as a cathode catalyst for oxygen reduction reaction (ORR) in alkaline fuel cells. The physical properties of rGO/MnO2/Ag have been investigated via several instrumental methods. This material exhibits a polycrystalline structure characterized by Ag/MnO2 microsphere formation as a result of Ostwald ripening. The X-ray diffraction and X-ray photoelectron spectroscopy data reveal that the MnO2 and Ag have been slightly alloyed and Mn presents with the dioxide form on rGO. The electrochemical properties of the electrocatalyst have been studied via several voltammetric methods. The results demonstrated that the rGO/MnO2/Ag has an excellent catalytic activity for ORR in alkaline media compared to the other tested electrodes. Particularly, it shows 1.2 times higher current density and better electron transfer rate at 0.3 V per O2 than that of 20 wt% Pt/C. The other kinetic analysis reveals that the O2 has reduced directly to H2O through a nearly four-electron pathway with better anodic fuel tolerance and duration performance than that of 20% Pt/C.

Electrochemical Deposition of Silver on Gold Electrodes in the Presence of Halogen Ions

Abstract Electrochemical reactions of silver in the presence of chloride and bromide ions were examined using cyclic voltammetry (CV) and electrochemical quartz-crystal microbalance measurements. In the presence of chloride ions, repeated CV cycles caused AgCl to deposit on the electrode. In contrast, reduction of silver ions in the presence of bromide ions to form metallic silver was very slow, and AgBr was not deposited on the gold electrode.

Increasing the activity and stability of chemi-deposited palladium catalysts on nickel foam substrate by electrochemical deposition of a middle coating of silver

The objective of this study was to enhance the activity and stability of the chemi-deposited palladium/nickel foam (Pd/Ni foam) electrode used in the electrochemical dechlorination process. The electrochemical deposition of silver onto a nickel foam substrate (Ag/Ni foam) was applied before the chemical deposition of palladium. The physicochemical properties of the resultant material (Pd/Ag/Ni foam) were characterized by X-ray diffraction and scanning electron microscopy. The results showed that the silver coating was in the form of spherical apophyses, and the palladium was dispersed finely on the surface of the Ag/Ni foam. Dichloroacetic acid was selected as an indicator to evaluate the activity and stability of the palladium catalyst. Pd/Ag/Ni foam electrode consistently had relatively higher dechlorination rate and current efficiency (CE) in the current density range of 1.5–10.5 mA cm −2 compared to the Pd/Ni foam electrode. Quantitative analysis of the main intermediates and final products involving monochloroacetic acid, acetic acid and the chloride ion further demonstrated the enhancement of electrochemical dechlorination by the presence of silver. Moreover, after five cycles of dechlorination, the CE for the Pd/Ni foam electrode decreased dramatically from 67% to 13%, whereas that for the Pd/Ag/Ni foam electrode was decreased by much less, from 78% to 62%, and the palladium loss was clearly reduced by the addition of a silver coating between the Ni foam and the Pd outer layer.

Electrochemical deposition of silver from 1-ethyl-3-methylimidazolium trifluoromethanesulfonate

Silver was successfully electrodeposited from the ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIm][TfO]) containing silver ions in various concentrations. The electrochemical windows of the electrolytes were determined by cyclic voltammetry. Moreover, the conductivity and the viscosity–density product were studied with electrochemical impedance spectroscopy (EIS) and electrochemical quartz crystal microbalance (EQCM). Potentiodynamic and potentiostatic depositions were performed at different temperatures. The morphology of the deposited Ag layers depends on temperature and concentration. Thus, by choosing the right experimental conditions one can optimize the properties of the deposited layers. The thus obtained layers can be used in different surface finishing processes, such as in decorative plating, catalysis or for electrical contacts.

Morphology of silver electrolytically precipitated from acetonitrile solutions of silver nitrate

The electrochemical deposition of silver was investigated from 0.01–0.1 M acetonitrile solutions of Ag NO3 by stationary and pulse current. An effect of the main parameters of the pulse current (duration and pause of pulse), concentrations of silver ions, time of electrolysis, and nature of support was considered on form and size of structural particles of deposit.

Sonoelectrochemical Deposition of Functional Composite Layers

Ultrasound was applied for the electrodeposition of metal/ceramic and metal/metal composites. Ni/ceria composites were deposited from Watts and sulfamate based electrolytes containing dispersed ceria using ultrasonic irradiation for the deagglomeration of oxide particles. The electrochemical deposition of silver at the tip of an ultrasonic horn probe using pulsed ultrasound was explored for its potential to electrodeposit Ni/Ag composites. First results are presented. Sonoelectrochemical processes were in part monitored in-situ by the electrochemical quartz crystal microbalance technique. Compositions of the electrodeposits were analyzed by energy dispersive spectroscopy and in part by electron probe microanalysis.

Development of new techniques for scanning electron microscope observation using ionic liquid

Based on our previous discovery that ionic liquid (IL) can be observed by a scanning electron microscope (SEM) without charging the liquid, we have developed several novel techniques for SEM observation. Coating of insulating sample with IL is useful for providing electronic conductivity to the samples like metal or carbon coating by vacuum vapor deposition. In this case, dilution of the IL with appropriate volatile solvent like alcohol is effective for coating thin layer of IL on the sample. As a biological sample, seaweed including IL was attempted to be observed by SEM. A seaweed leaf swollen by water was put in an IL bath and the bath was put in an outgassed desiccator to replace water in the seaweed leaf with IL. The resulting sample gave a SEM image of the swollen seaweed whose thickness was several times larger than dried one. Furthermore, the introduction of the IL in vacuum chamber allowed us to develop the in situ electrochemical SEM observation system. Using this system, we observed changes in polypyrrole film thickness caused by the redox reaction of the film and the electrochemical deposition of silver and its oxidative dissolution. It was also found that the energy dispersive X-ray fluorescence (EDX) analysis was available even for the electrode polarized in IL.

An electrochemical amplification immunoassay using bi-electrode signal transduction system

An electrochemical immunoassay technique has been developed based on the sensitive detection of the enzyme-generated product with a bi-electrode signal transduction system. The system uses two separate electrodes, an immunoelectrode and a detection electrode to form a galvanic cell to implement the redox reactions on two different electrodes, that is the enzyme-generated reductant in the anode region is electrochemically oxidized by an oxidant (silver ions) in the cathode apartment. Based on a sandwich procedure, after immunoelectrode with antibody immobilized on its surface bound with the corresponding antigen and alkaline phosphatase conjugated antibody successively, the immunoelectrode was placed in enzyme reaction solution and wired to the detection electrode which was immerged into a silver deposition solution. These two solutions are connected with a salt bridge. Thus a bi-electrode signal transduction system device is constructed in which the immunoelectrode acts as anode and the detection electrode serves as cathode. The enzyme bound on the anode surface initiates the hydrolysis of ascorbic acid 2-phosphate to produce ascorbic acid in the anode region. The ascorbic acid produced in the anodic apartment is electrochemically oxidized by silver ions coupled with the deposition of silver metal on the cathode. Via a period of 30 min deposition, silver will deposited on the detection electrode in an amount corresponding to the quantity of ascorbic acid produced, leading to a great enhancement in the electrochemical stripping signal due to the accumulation of metallic silver by enzyme-generated product. Compared with the method using chemical deposition of silver, the electrochemical deposition of silver on a separate detection electrode apartment avoids the possible influence of silver deposition on the enzyme activity.

Electrochemical Deposition of Silver in Room-Temperature Ionic Liquids and Its Surface-Enhanced Raman Scattering Effect

The use of room-temperature ionic liquids (RTILs) as media for electrochemical application is very attractive. In this work, the electrochemical deposition of silver was investigated at a glassy carbon electrode in hydrophobic 1-n-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) and hydrophilic 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4) RTILs and in KNO3 aqueous solution by cyclic voltammetric and potentiostatic transient techniques. The voltammograms showed the presence of reduction and oxidation peaks associated with the deposition and dissolution of silver from AgBF4 in both BMIMPF6 and BMIMBF(4), resembling the redox behavior of AgNO3 in KNO3 aqueous solution. A crossover loop was observed in all the cyclic voltammograms of these electrochemical systems, indicating a nucleation process. From the analysis of the experimental current transients, it was shown that the electrochemical deposition process of silver in these media was characteristic of 3D nucleation with diffusion-controlled hemispherical growth, and the silver nucleation closely followed the response predicted for progressive nucleation in BMIMPF6 and instantaneous nucleation in KNO3 aqueous solution, respectively. Compared with these two cases, the electrochemical deposition of silver in BMIMBF4 deviated from both the instantaneous and progressive nucleation models, which could be controlled by mixed kinetics and diffusion. On the basis of the experimental results, it was shown that parameters such as viscosity and water miscibility of RTILs would affect the electrodeposition behavior of silver. Atom force microscopy was employed to probe the surface morphology of the silver deposit, and it showed that the shining electrodeposit of silver was fairly dense and separate nanoclusters of <100 nm were in evidence, corresponding to an island growth model. The strongly enhanced Raman scattering from the monolayer film of 4-mercaptobenzoic acid demonstrated that as-prepared silver nanoparticular film was surface-enhanced Raman scattering (SERS) active. The enhancement factor was calculated to be up to 9.0 x 10(5) and 1.0 x 10(6) for the silver film obtained in BMIMPF6 and BMIMBF4 RTILs, respectively.

Electrochemical nucleation and growth of nano- and microparticles: some theoretical and experimental aspects

The article reviews recent theoretical and experimental advances in the field of electrochemical nucleation and growth. Experimental data for simultaneously determined ‘number of nuclei–time’ and ‘current–time’ relationships obtained during the electrochemical deposition of silver on a glassy carbon working electrode are analysed in terms of the theoretical models accounting for the spread of exclusion zones around growing stable clusters. Information is obtained on the applicability of the theoretical formulae for the number N( t) of nuclei and for the current i( t) of progressive nucleation. Possible reasons for the registered disagreement between theory and experiment are discussed.

Electrochemical deposition of silver and gold from cyanide leaching solutions

A systematic voltammetric study developed in this work allows the determination of the potential range at which the selective deposition of gold and silver is carried out in the presence of a high content of copper. As a first approach, laboratory solutions prepared with a high content of cyanide and copper and low values of gold and silver are used; later, the methodology is applied to leaching solutions of industrial origin. The chemical speciation and microelectrolysis studies showed that copper deposition occurs at more negative potentials than deposition of gold and silver. Also, the voltammetric study of a cyanide solution containing low concentrations of Au(I) and Ag(I), free of and with high concentration of Cu(I) was carried out. The study shows the potential range at which Au(I) and Ag(I) are reduced despite the high concentration of the Cu(I) ions. The deposition of gold and silver was not interfered with by the high concentration of Cu(I) ions when the leaching solution was electrolyzed in a laboratory electrochemical reactor FM01-LC with a reticulated vitreous carbon (RVC) cathode.

Self-Assembly of Alkanoic Acids on Gold Surfaces Modified by Underpotential Deposition

We present an alternative to self-assembled monolayers (SAMs) of ω-functionalized alkanethiols on gold. Substrates utilized here are gold modified by electrochemical deposition of silver or copper monolayers. The metal adlayers promote anchoring of carboxylate headgroups and assembly of ω-alkanoic acids, which would otherwise exhibit no chemisorption on bare gold. Infrared reflectance absorption spectroscopy shows that the films exhibit general characteristics of SAMs. The binding scheme is different from SAMs of alkanethiols on gold and alkanoic acids on silver or copper surfaces. Wetability results obtained from contact angle measurements indicate that such films are more reproducible than SAMs of alkanoic acids on bulk silver and copper.

Study of the mechanism of the electrochemical deposition of silver from an aqueous silver iodide suspension

The present work examines the reduction of solid silver iodide on a silver electrode and proposes a mechanism for this process. Voltammetric and coulometric studies for the steady and transient states showed adsorption of silver iodide at the electrode depending on its concentration; this adsorption is in accordance with the Langmuir isotherm for low concentrations and with multi-layer models (such as the BET isotherm) for higher concentrations. Reduction of silver iodide at the silver electrode can take place through several processes such as direct reduction of solid particles, or reduction of the adsorbed silver iodide and involves the formation of a dendritic silver deposit not adhering to the electrode and free iodide in solution. Silver is then recovered easily by filtration of the initial suspension.

Surface enhanced infrared absorption spectroscopy (SEIRA) using external reflection on low-cost substrates

A novel approach for spectroscopic trace analysis is introduced by combining surface enhanced infrared absorption (SEIRA) spectroscopy with external reflection techniques on disposable inexpensive substrates. SEIRA-active surfaces produced by electrochemical deposition of silver on smooth metal surfaces and glass improve the sensitivity of IR reflection measurements significantly since the infrared absorption of organic substances such as p-nitrobenzoic acid is considerably increased in the vicinity of rough noble metal surfaces. The enhancement properties of thus prepared substrates are characterized and compared using IR-spectroscopy. These low-cost substrates used in single- and multiple external reflection arrangements, respectively, yield a significant increase of the detection level compared to conventional reflection absorption infrared spectroscopy (RAIRS) up to one order of magnitude. Hence, a notable step towards a wide-spread application of SEIRA in routine IR reflection analysis is presented.

Ag-layers on non-ferrous metals and alloys. A new substrate for surface enhanced Raman scattering (SERS)

Substrates for surface enhanced Raman scattering (SERS) are mainly produced by electrochemical roughening of noble metal electrodes, sputtering of noble metals on glass slides or preparation of colloids. In this work SERS of pyridine and nicotinic acid on a newly developed SERS substrate was obtained using an FT-Raman spectrometer with excitation in the near-IR employing a Nd:YAG laser at 1064 nm. This new technology is based on the electrochemical deposition of silver on surface roughened non-ferrous metals and alloys. Although this new preparation method needs only few quantities of noble metals and no expensive equipment, excellent SERS signals being approximately 700 000 times (nicotinic acid) up to 1.4 million times (pyridine) stronger than those of conventional Raman measurements could be observed. Finally, the dependency of the signal enhancement on the chloride concentration was investigated for pyridine.

Electrochemical Deposition of Silver from a Low Cyanide Concentration Bath

The silver reduction process was studied in a new, low cyanide concentration solution in which the predominant species is the ion and the pH is fixed by the presence of potassium pyrophosphate. The electrochemical reduction of silver occurs via an adsorbed electroactive species assumed to be . The silver reduction appears to be a quasi‐reversible process at 20°C, and its kinetic parameters are presented as well as the effect of temperature in a 10 to 60°C range; silver reduction is fast when the temperature is high, and the activation energy was evaluated. Linear sweep voltammetry and the use of an electrochemical quartz crystal microbalance prove the existence of the adsorbed electroactive species and additional evidence was found by chronopotentiometry.

Dendritic and Fractal Patterns in Electrochemical Deposition of Silver

Electrochemical deposition were carried out using silver nitrate (AgNO3), with Langmuir monolayer at the interface of solution. Pattern formation was studied as a function of applied voltage and surface pressure. We found four different growth forms in this system. A transition from ordered dendritic crystals to disordered ramified patterns is found when the applied voltage increases most strikingly, from dendritic crystal to disordered ramified patterns, a dense two-dimensional silver film with fractal clearance is obtained.