Potential Step Technique Research Articles

Efficient removal of uranium (VI) with a phytic acid-doped polypyrrole/ carbon felt electrode using double potential step technique

In order to efficiently extract uranium from uranium-containing wastewater, a novel acid doped polypyrrole/carbon felt (PA-PPy/CF) electrode was prepared via a facile electrodeposition method. For this material, PA and PPy combined to form a stable chemical structure by a charge compensation mechanism. The electrochemical characterization results showed that PA-PPy can significantly accelerate the electrochemical reduction rate of uranium ions. Moreover, a double potential step technique (DPST) was applied to prevent water splitting and maintained the electrocatalytic reduction activity of the surface groups during the electrochemical adsorption process. The removal efficiency obtained by the DPST method was six times higher than that obtained by the conventional chemical adsorption. When the concentrations of uranyl nitrate were 10, 20, 50, and 100 mg/L, the removal efficiencies of uranium were 98.8%, 98.1%, 94.6%, and 93.7%, and the adsorption capacities of uranium were 164.7, 326.9, 788.5, and 1562.0 mg/g, respectively. This material also showed an excellent recycling performance and remarkable selectivity for uranium ions. This work may shed light on the development of removal system for uranium (VI).

Electrochemical deposition of uranium oxide with an electrocatalytically active electrode using double potential step technique

The development of effective uranium-removal techniques is of great significance to the environment and human health. In this work, a double potential step technique (DPST) was applied to remove U(VI) from uranium-containing wastewater using a carbon felt electrode modified by graphene oxide/phytic acid composite (GO-PA@CF). The application of DPST can inhibit water splitting and prevent GO-PA from adsorbing other interfering ions in wastewater. The GO-PA composite can effectively accelerate the electrochemical reduction rate of U(VI), which significantly improved the electrochemical deposition rate of uranium oxide. As a result, the maximum removal efficiency and maximum removal capacity of GO-PA@CF electrode reached 98.7% and 1149.3 mg/g, respectively. The removal efficiency remained 97.2% after five cycles of reuse. Moreover, the removal efficiency of GO-PA@CF electrode can reach more than 70% in simulated wastewater.

Adsorption and Oxidation Dynamics of Disperse Orange 3 on a Polycrystalline Pt Electrode Studied by In Situ Second Harmonic Generation

Adsorption mechanisms and electrochemical reaction mechanisms at the molecular level are fundamental issues in electrochemistry. Here, we used in situ second harmonic generation (SHG) combined with in situ UV–vis spectra and potential step techniques to investigate the dynamics of the adsorption and oxidation of 4-amino-4′-nitroazobenzene (disperse orange 3, DO3) molecules on a polycrystalline Pt electrode. Time-dependent SHG spectra with different polarization combinations under certain potential steps confirmed that the SHG intensity change in the DO3 molecules resulted from the number density change rather than the orientation angle change. A double potential step experiment and UV–vis spectra verified that the number density change arose from the cooperative effects of adsorption and oxidation of DO3 at the interfaces. Under an applied potential, the adsorption rate of DO3 was greater than the electrooxidation rate in the first hundred seconds until full coverage was achieved and the maximum SHG intensity was reached. Subsequently, the oxidation of DO3 dominated until equilibrium was established, while the SHG intensity stabilized. In addition, the time-dependent SHG spectra showed that the rate constants of the adsorption process and the oxidation reaction were strongly dependent on the potential. This work provides in-depth insights into the adsorption and electrochemical reaction at electrode/solution interfaces.

(Invited) Additives in Cu Plating for Microelectronics Applications

Electrodeposition is a prevailing method in fabrication of Cu interconnects in microelectronics due to its ability to fill complex structures having a wide range of critical dimensions. A typical acidified Cu electrolyte contains a number of additives, organic and inorganic species in ppm amounts, with a specific role in the plating process. The additives in Cu plating have been extensively studied in the past couple of decades, and grouped according to their role in filling/creating features for microelectronics applications. This categorization is not a uniform one, and it might differ from author to author. In one popular convention, organic additives in the so-called three-component plating bath are named accelerator, suppressor and leveler, with their names hinting at how they influence Cu deposition. Ultimately, it is thanks to these additives that defect-free Cu features ranging from tens of nanometers to hundreds of micrometers can be economically fabricated. However, it is not enough to successfully fill a given single feature. The same has to be done for all the features on a 300 mm wafer, and then performed reproducibly over and over again. So, one needs to monitor the state of the electrolyte, i.e. of all the bath constituents, and either replace or replenish the electrolyte when the need arises. Additives could also have a strong influence on the physical properties of the deposit and therefore have a strong influence on the post-plating processing results. An additive that promotes void-free deposition of Cu structures in the end might not be used in a production line if it creates issues in the processing steps following electrodeposition. In our presentation we focus on a number of specific examples showing the effect of additives on nucleation and growth of Cu, propagation of Cu fronts on resistive substrates, post-plating processing, and their use in substrate surface modifications. A closer look is taken into in situ microscopic and electrochemical techniques and their use in studies of electrochemical nucleation and growth of Cu. We discuss advantages and drawbacks of potential step and galvanostatic deposition techniques in determining nucleation and growth parameters, and selection criteria for additive sets for a given plating task. We demonstrate that substrate surface modifications prior to plating could help simplify bath composition, i.e. eliminate need for some additives in the electrolyte, or improve the filling performance of the given plating bath. We also give examples of additives that promoted void-free filling of features but also influenced physical/mechanical properties of the final product in such a way that rendered it unusable in a specific application.

Electrochemical sensing of terabromobisphenol A at a polymerized ionic liquid film electrode and the enhanced effects of anions

1-[3-(N-pyrrolyl)propyl]-3-butylimidazolium tetrafluoroborate (PPBimBF4), a functional ionic liquid, was prepared successfully. It was employed as a monomer to fabricate a polymerized ionic liquid (PIL) film on glassy carbon electrode surface with potential step technique. Scanning electron microscopy (SEM) and electrochemical impedance microscopy (EIS) were used to characterize the morphology and the electrochemical properties of the PIL film electrode, respectively. Voltammetry was applied to investigate the electrochemical behaviors of tetrabromobisphenol A (TBBPA) at the PIL film electrode. An irreversible electrochemical oxidation process was found for TBBPA at the PIL film electrode surface. The influence of some anions on the electrochemical response of TBBPA was also investigated. The results demonstrated that the PIL film with dodecyl sulfonate anion [poly(PPBim-DS)] can give maximum peak current for TBBPA. Experimental conditions including the film thickness, pH values, accumulation potential, and accumulation time were optimized for TBBPA determination. Under optimized conditions, an effective electrochemical method for TBBPA determination was developed. The oxidation peak current is linearly related to the TBBPA concentration in the range from 5.0 × 10−8 to 1.0 × 10−5 mol L−1 with a detection limit of 2.0 × 10−8 mol L−1 (S/N = 3). In addition, the electrochemical sensing platform was used to detect TBBPA in South Lake water samples.

Electrochemical Reduction of CO2 on Copper Oxidized By Electrochemical Methods

The electrochemical oxidation of copper surface in alkaline solution results in the formation of different products, which are a function of scan rate and concentration of OH- ions. It has been found that, the electro-oxidation results in oxide film on copper surface consist of Cu2O, Cu(OH)2 and CuO. The scanning electron microscopy (SEM) images of copper foils oxidized by linear sweep voltammetry at different scan rate show a systematic growth of oxides on the copper surface. At low scan rate growth of oxide takes place resulting in needle like structures projecting outwards from copper surface. Further, the density of these needles of oxides decreases as the scan rate increases. A similar behaviour was also observed in the chronoamperometry experiments performed at different potential and for different time duration. The length and the density of needles increase with increase in time when the applied potential was in potential region of peak B. On the other hand, at more negative potential and low concentration OH- ions instead of needles, a layer of oxide particles were observed. The x-ray photoelectron spectroscopy (XPS) analysis of oxidized copper surface shows the presence of Cu2O, Cu(OH)2and CuO in the oxide layer and the percentage of CuO increases as the density of needles increases on the surface. It has found that the catalytic activity of the copper obtained by reducing it from its oxides is more than that of the original polycrystalline copper foil for CO2reduction. The oxidation of copper surface can be achieved either by annealing in air or oxygen, or by electrochemical oxidation. Further, electrochemical oxidation of copper foil can be performed either by potential sweep or potential step techniques. Here, the oxidation of copper surface was carried out by chronoamperometry (CA), linear sweep voltammetry (LSV) as well as cyclic voltammetry (successive oxidation and reduction cycles) in Ar saturated 0.5 M KOH solution. The copper foil was oxidized by CA at -0.1 V for 30 minutes and LSV at scan rate of 0.5 mV/s from -1.2 to 0.5 V in Ar saturated 0.5 M KOH. The five cycles of CVs were carried out at a scan rate of 0.5 mV/s in Ar saturated 0.5 M KOH between -1.2 to 0.5 V. The SEM images shows that the needle like growth of oxides gets reduced back to copper in first few minutes of the electrochemical reaction when applied potential is more negative than hydrogen evolution. These in turn have been used for electrochemical reduction of CO2. The main product of CO2 reduction in aqueous phase was found to HCOO- and the gas phase analysis revealed predominantly hydrogen molecule. Faradaic efficiency for formic acid on copper foil oxidized by CV was higher than that for copper foil oxidized by the CA and LSV. The reason this observation may be the amount of active copper produced on the polycrystalline copper from the reduction of the copper oxides. This has been verified from the amount of charge transferred during the oxidation of copper which is highest for the CVs as with each cycle the peak current of both the peaks observed during oxidation of copper increases. During oxidation of copper foil by CV in fifth cycle a total charge of ~0.70 C/cm2 charge was transferred, whereas, during LSV a total of ~0.45 C/cm2 and during CA at total of ~0.30 C/cm2 of charge was transferred. Thus indicating more oxidation during CV than LSV and CA, and hence more amount of active copper will be produced on the copper surface resulting in increased faradaic efficiency of formic acid. Figure 1

Manganese oxide nanoflakes/multi-walled carbon nanotubes/chitosan nanocomposite modified glassy carbon electrode as a novel electrochemical sensor for chromium (III) detection

In this research a nanocomposite containing chitosan (Chit) and maltiwalled carbon nanotubes (MWCNTs) was applied as platform for immobilization of electrodeposited manganese oxide (MnOx) nanostructures. First, glassy carbon (GC) electrode modified with thin film of Chitosan/MWCNTs nanocomposite. Then MnOx nanostructures was electrodeposited onto Chitosan/MWCNTs modified GC electrode using combination of constant potential step (0.6V) and cyclic voltammetry(0.3–0.6V) techniques. The XRD patterns and scanning electron microscope images indicated immobilization of uniformly MnOx nanoflakes with high crystallite onto MWCNTs/Chit film. The modified electrode shows a well-defined redox couple for Mn2+/MnO2 system. Charge transfer coefficient (α), electron transfer rate constant (ks) and surface concentration (Γ) were 0.394, 3.44s−1 and 3.3×10−11molcm−2, respectively. The modified electrode showed excellent electrocatalytic activity toward oxidation of chromium (III) at natural pH solutions. Cyclic voltammetry and hydrodynamic amperometery were applied as measuring techniques for chromium detection. Detection limit, sensitivity and linear concentration range of the sensor were, 0.3 (μM), 18.7nAμM−1 and 3μM to 200μM, respectively. Moreover, the sensor retained about 90% of its original response toward Cr(III) after storage three months in ambient condition. Furthermore, the sensor response toward different common interferences was negligible. Finally, the developed sensor was applied for the detection of Cr(III) in real samples with satisfactory results.

Dynamics of Oxidation of Well-Defined Adsorbed CO Phases on Pt(111) in Aqueous Acidic Electrolytes: Simultaneous in Situ Second Harmonic Generation and Differential Reflectance Spectroscopy

The oxidation dynamics of the well-defined (2 × 2)-3CO (θCO = 0.75) and √19 × √19R23.4°-13CO (θCO = 0.68) CO adlayer phases on quasi-perfect Pt(111) facets have been examined in CO-saturated 0.1 M H2SO4 aqueous solutions via a combination of simultaneous, in situ, time-resolved, second harmonic generation (SHG, λinc = 590 nm), normalized differential reflectance spectroscopy (ΔR/R, λinc = 633 nm), and potential step techniques. For both of these phases, the onset of oxidation of COads was found to be delayed with respect to the time at which the potential was stepped to values positive enough, Eox, to promote oxidation of the entire CO adlayers. This induction time, τind, was much longer for the (2 × 2)-3CO (few tens of milliseconds) compared to the √19 × √19R23.4°-13CO phase (few milliseconds) and decreased monotonically for both of the phases as Eox was increased. Furthermore, for a fixed Eox, the oxidation rates, as measured by the optical techniques, were higher for the √19 × √19R23.4°-13CO compared t...

Potential Step Study of Intercalation Processes

Potential step technique of intercalation process study is used for lithium intercalation in ferritic-carbon alloys, hydrogen insertion in titanium and anodic oxidation of nickel oxide and nickel powders. As a result it was found, that there are a lot of general regularities of intercalation processes, which can express in terms of piecewise EMF function and staging of kinetic steps of intercalation processes.

A novel nanoporous film electrode based on electrochemical polymerization of ionic liquid and its application in sensitive determination of magnolol

A polymeric film modified glassy carbon electrode was electrochemically fabricated with potential step technique using 1-butyl-3-[3-(N-pyrrole)propyl] imidazolium tetrafluoroborate ionic liquid as a monomer. Followed by being treated with sodium dodecyl sulfonate solution, a hydrophobic film bearing poly{1-butyl-3-[3-(N-pyrrolyl)propyl]imidazolium dodecyl sulfonate} moiety was modified onto electrode surface. The substitution was confirmed by X-ray photoelectron spectroscopy. The morphology of the polymeric film electrode surface was characterized with scanning electron microscopy. Electrochemical behaviors of magnolol at the hydrophobic polymeric film electrode were systematically investigated with voltammetry. Compared with the unmodified glassy carbon electrode, the oxidation peak shift slightly towards positive potential and the oxidation peak current significantly increased. Under optimal conditions, the oxidation peak current was linearly related to the magnolol concentration in the range of 1.0 × 10(-8) to 1.0 × 10(-6) mol L(-1) and 1.0 × 10(-6) to 5.0 × 10(-5) mol L(-1). The detection limit was estimated to be 4.55 × 10(-9) mol L(-1) (S/N=3). The polymerized ionic liquid film electrode was successfully used to analysis magnolol in M. officinalis. The result was consistent with that obtained by high performance liquid chromatography.

Selective electrochemical determination of dopamine, using a poly(3,4-ethylenedioxythiophene)/polydopamine hybrid film modified electrode

The selective determination of dopamine (DA) was performed in the presence of ascorbic (AA) and uric acid (UA), using a platinum electrode (Pt) modified with a hybrid film of poly(3.4-ethylenedioxythiophene)/polydopamine (PEDOT/PDA). PEDOT was obtained using a potential step technique on a bare Pt electrode. PDA was subsequently obtained on the PEDOT coated electrode by cyclic voltammetry. The PDA thickness effect allows observing just the DA oxidation signal in the presence of some interferents, e.g. uric acid (UA) and ascorbic acid (AA). The formed PEDOT/PDA hybrid film was compared with PEDOT in a K4[Fe(CN)6] solution in PBS of pH 7.4. Inhibition of the [Fe (CN)6]4−/[Fe(CN)6]3− redox couple on the PEDOT/PDA surface was observed, indicating the film bears a negative surface charge. The different electrodes were characterized by SEM and FTIR. DA amperometric determination was performed in the presence of AA and UA. The sensor proved to be selective toward DA. Calibration curves, with a linear range 1.5×10−6 to 50×10−6molL−1, enabled the limit of detection and quantification to be determined, namely 0.65×10−6molL−1 and 1.77×10−6molL−1, respectively. The described methodology permits, therefore, to propose this modified electrode as a new electrode for DA determination in the presence of interferents.

Determination of the rate-determining step in the electrochemical oxidation of Li metal at the Li negative electrode/Li2S–P2S5 solid electrolyte interface

The rate-determining step in electrochemical oxidation reaction of Li metal at the interface between an Li negative electrode and xLi2S–(100−x)P2S5 (x = 75, 70 or 67) solid electrolyte was determined on the basis of the study on Ag+ ion conductive solid electrolytes. For this purpose, potential step technique using a microelectrode was applied. Two possible rate-determining steps, the diffusion of Li+ ion vacancies and the reaction between interstitial Li+ ions and Li+ ion vacancies, were assumed, and we found the diffusion of Li+ ion vacancies is the rate-determining step in the present study. We also evaluated the exchange current density (i0) of the Li/Li+ couple reaction and ionic conductivity (κ) of each solid electrolyte. Both i0 and κ were increased as the x value was increased, suggesting that the conductivity of Li+ ions or the rate of the diffusion of Li+ ion vacancies was closely related to the rate of the Li/Li+ couple reaction.

Electrocrystallization mechanism of iron phosphate coatings onto mild steel electrode surfaces

Samples of mild steel AISI-SAE 1018, 1045 and 1080 were electrochemically phosphatised, both potentiodynamically and potentiostatically, in a concentrated H3PO4 aqueous solution. The conversion coating layers formed were characterised by means of scanning electron microscopy and energy-dispersive x-ray analysis. The kinetics and mechanisms of the electrocrystallization process of FePO4·2H2O(c) films were studied using the potential step technique. It was found that the mechanism governing the formation of FePO4·2H2O(c) anodic film was common for all the steel samples, namely, the overall electrodic process comprises four different simultaneous contributions to the overall current (j(t)). The individual contributions were: j ad(t), the current density contribution due to H3PO4 adsorption; j d(t), the current density involved during electrodissolution of iron of the steel electrode in the zones which were not covered yet by the FePO4·2H2O(c) film; j g(t), the current density contribution due to 2D nucleation and growth of an insoluble FePO4·2H2O(c) conducting adlayer; and j f(t), the current due to the growth of the passive layer induced by electrodissolution of iron metal and transport of the resulting Fe(II) ions through the FePO4·2H2O(c) film. However, each stage contributed to the overall process in a different manner, depending upon the carbon contents. The results from voltammetry indicated that it is possible to establish the potential at which the FePO4·2H2O(c) film begins to form and that this was also a function of the carbon contents.

New Insights into the Mechanism and Kinetics of Adsorbed CO Electrooxidation on Platinum: Online Mass Spectrometry and Kinetic Monte Carlo Simulation Studies

The electrooxidation of saturated CO adlayers on Pt/Vulcan and polycrystalline Pt has been studied by potential step techniques combined with differential electrochemical mass spectrometry (DEMS) and kinetic Monte Carlo (KMC) simulations. DEMS was used to selectively monitor the COad electrooxidation, via the CO2 formation rate, without interference from the pseudocapacitive double-layer charging and electrode surface oxidation, while the KMC simulations were employed to understand the mechanism and kinetics of COad electrooxidation at the molecular level. Our DEMS data show that the current transients of COad electrooxidation on polycrystalline Pt and Pt/Vulcan exhibit an initial spike immediately after the potential step, followed by a slow current decay and finally a broad main peak. The temporal evolution of the transients depends strongly on the oxidation potential applied, resulting in the overlap of the initial spike and the main peak for high potentials. A model is proposed to account for the observed phenomena. On the basis of this model, we developed a kinetic Monte Carlo simulation code specific to the electrooxidation of adsorbed CO on Pt. The simulations reproduce the experimental data very well, confirming the robustness of our model.

Anhydrous Proton-Conducting Membrane Based on Poly-2-Vinylpyridinium Dihydrogenphosphate for Electrochemical Applications

Anhydrous electrolytes with high proton conductivity and adequate chemical stability in the temperature range of 120-180 °C can be very useful in electrochemical devices such as fuel cells, sensors, and electrolyzers. Developing such proton-conducting materials has been challenging. We have fabricated and characterized the performance of such membranes, based on poly-2-vinylpyridinium dihydrogenphosphate (P2VP-DHP), that can operate in the range of 105-180 °C under anhydrous conditions. The ionic conductivity of the membrane was 0.01 S cm(-1) at 140 °C. Proton conduction occurs by ionization of the quaternary ammonium group and by Grotthus-type transport that involves the rapid rotation of the dihydrogenphosphate anion. The activation energy for proton transport was 50 kJ/mol. The transport number of the proton was measured by impedance spectroscopy and potential-step techniques. The measured value was in the range of 0.17-0.20. A membrane-and-electrode assembly using the P2VP-DHP was tested as an electrochemical hydrogen pump. This demonstration shows the advantage of membranes based on a polymer amine salt in electrochemical applications that require operating under water-free conditions. Weight loss measurements at 120 °C in air confirmed the thermal and oxidative stability of the membrane. The properties of the P2VP-DHP membrane reported here provide the basis for further development of proton-conducting polymer electrolyte membranes for operating temperatures above 100 °C in anhydrous environments.

Influence of chelating agents on the tribocorrosion of tungsten in sulphuric acid solution

The corrosion and tribocorrosion of tungsten in 0.01 M H 2SO 4, without and with the presence of lactic acid and phosphoric acid as chelating agents was studied here. The passive behaviour was characterised using potentiostatic polarization and potential step techniques combined with rotating disk electrodes. Surface analysis techniques (XPS, AES) were used to assess surface chemistry. The tribocorrosion of tungsten was investigated using a tribometer equipped with an electrochemical cell operating at applied passive potentials of 0.2 V and 1.0 V. Under static corrosion conditions chelating agents were found to enhance passive film dissolution and to decrease the passive film thickness. Despite this, the effect of the investigated chelating agents was limited under tribocorrosion conditions. Indeed, only lactic acid at the most anodic potential lead to significant differences in material removal by impeding the formation of protective tungsten oxide tribolayers. The discrepancy on the effect of chelating agents in corrosion and tribocorrosion was explained in terms of the different involved time constants.

Study of the Copper Electrodeposition on Titanium Electrodes

The electrodeposition of copper on titanium electrodes was investigated using cyclic voltammetry and a potential step technique in 5x10-3 M CuSO4, 1M (NH4)2SO4 and pH values of 8, 9 and 10.3. Voltammetric analysis showed that the reaction is carried in two steps. The first corresponds to the reduction of Cu(NH3)2+ to Cu(NH3)2 +, possibly controlled by electronic transfer. The second corresponds to the reduction of Cu(NH3)2 + to Cu(0). The electrocrystallization mechanism and the coupled reactions are pH function. The overcrossing potential, Ec, remains constant, and may be related to the thermodynamic potential. The current transients confirmed nucleation and growth process. There is a possible kinetically controlled reaction occurring on the first Cu layer of the deposit or the Ti substrate and it will be confirmed on a later work by applying the appropriate model.

Selective Detection of As(V) with High Sensitivity by As-deposited Boron-doped Diamond Electrodes

Abstract Electrochemical selective detection of not only As(III) but also As(V) has been investigated by anodic stripping voltammetry. Here, instead of using modified working electrodes, simple as-deposited boron-doped diamond (BDD) electrodes were used with the addition of gold ions in the sample solution as a catalyst for the electrochemical reaction. A potential-step technique was performed to minimize the hydrogen evolution effect that occurs at the highly negative potential such as −1.5 V (vs. Ag/AgCl) for the reduction of As(V). The present method realized very high sensitivity with an experimental detection limit of 12 ppb and excellent stability for the detection of both As(III) and As(V) as well as mixed solutions of these forms.

Underpotential deposition of cobalt onto polycrystalline platinum

An electrochemical study of cobalt electrodeposition onto a polycrystalline platinum electrode from an aqueous solution (10−2 M CoCl2 + 1 M NH4Cl (pH 9.5)) was carried out through cyclic voltammetry and potential step techniques. Analysis of the voltammetric data clearly showed that a cobalt adlayer is formed during the application of potential in the underpotential deposition (upd) region. Formation of this cobalt adlayer involved the simultaneous presence of both adsorption and 2D nucleation processes. Cobalt adlayers obtained by linear voltammetry in upd region were analyzed employing diffuse reflectance spectroscopy (DRS). By using theoretical quantum studies at PM6//HF/LANL1MB level, it was possible to assign the peaks obtained by DRS at 328 and 337 nm to the cobalt adsorption on Pt(111) and Pt(100), respectively, while the signals recorded at 355 and 362 nm were related with the clean platinum surfaces Pt(100) and Pt(111). Also, quantum calculations at the PM6 level indicated that the energy formation order is Co-Pt(100) > Co-Pt(111) > Co-Pt(110) > Co-Co(surface).

Electrochemistry of Copper(I) Oxide in the 66.7–33.3 mol % Urea–Choline Chloride Room-Temperature Eutectic Melt

The electrochemistry of Cu(I) oxide was examined in the 66.7–33.3% mole fraction (m/o) urea–choline chloride melt. Electrochemical parameters that were measured include the standard heterogeneous rate constant and transfer coefficient of the Cu(I)/Cu(II) reaction and the Cu(I) diffusion coefficient. Data about the density, equivalent conductance, and absolute viscosity of this melt were obtained over the temperature range of 298–353 K. The conductivity and viscosity exhibited the non-Arrhenius behavior typical of glass-forming liquids. Overall, the physicochemical properties of the urea–choline chloride melt are comparable to those of common room-temperature ionic liquids. The electrodeposition of Cu was examined on glassy carbon and platinum electrodes by using potential-step techniques. The critical number of atoms required for the formation of a stable nucleus on glassy carbon was , indicating that active sites on the electrode surface served as critical nuclei. Cu deposits on Ni substrates were dense, nodular, and compact.