Chronoamperometric Transients Research Articles

Improving the Corrosion Resistance of Anodized Al 1050 Alloy by Sealing in Cerium-Containing and Mixed Sodium Phosphate Mono Basic and Calcium Nitrate Solutions

This investigation presents results on the improvement of the corrosion-protective effect of consecutive sealing treatments of anodized Al 1050 (AlAnod). The treatments were performed in cerium-containing and mixed NaH2PO4 + Ca(NO3)2 solutions. The changes of the surface morphology, structure and chemical composition, chemical state of the elements, and basic corrosion parameters of the studied systems were investigated by SEM, EDXS, XRD, XPS, and a complex of electrochemical techniques (PDP, EOCP vs. timeplot, chronoamperometric transients, Rp and CR at EOCP, etc.). The results obtained show that the basic components of the obtained sealing conversion layers (before and after exposure to model Cl−-containing corrosion media) are characterized by Ca10(PO4)6(OH)2, AlO(OH), CePO4, and CeAlO3 (after the corrosion tests, they are converted to insoluble Me-PO3 and Me-P4O10). We conclude that the observed decrease in the corrosion rate of Al and the corresponding increase in the polarization resistance are accomplished by the two-step sealing treatment, which fills up the AlAnod pores with insoluble deposits.

Additives for Superconformal Gold Feature Filling

An overview of the effect of additives on Au electrodeposition from Na3Au(SO3)2 based electrolytes is presented with an emphasis on filling of fully metallized recessed surface features such as trenches and vias. The impact of heavy metal additives Tl+, Pb2+, and Bi3+ is reviewed and accompanied by a brief survey of the effects of Sb3+, Te4+, SeCN−, 3-mercapto-1-propanesulfonic acid (MPS) and polyethyleneimine (PEI) additions. The addition of Tl+, Pb2+, Bi3+ or Sb3+ accelerates the kinetics of Au(SO3)2 3− reduction to Au, as manifest in hysteretic voltammetry and rising chronoamperometric transients, and yields bright specular deposits. Gold deposition with Pb2+ addition exhibits superconformal filling in sub-micrometer trenches while Bi3+ addition induces a more extreme bottom-up filling, but Tl+ and Sb3+ additions yield essentially conformal deposition for the conditions examined. Modest acceleration and hysteresis observed with Te4+ addition reflect roughening due to limited nucleation, 3D growth and delayed coalescence, rather than catalysis, and are associated with conformal feature filling. Unlike the other additives, SeCN−, MPS and PEI inhibit the deposition kinetics. Breakdown of suppression during deposition in micrometer size trenches is biased toward recessed surfaces where the flux of suppressor is constrained, yielding localized deposition and superconformal filling.

Effect of Cu(I) ion on electrodeposition of zinc from ChCl-urea deep eutectic solvent

The effect of Cu(I) ions on the electrodeposition of zinc from ChCl-urea-ZnO deep eutectic solvent (DES) was investigated through electrochemical measurement and the deposit characterization. The cyclic voltammetry and cathodic polarization analyses demonstrated that Cu(I) ions obviously decreased the nucleation potential of Zn(II) and promoted the Zn(II) reduction reaction. The analysis of the chronoamperometric transients indicated that the nucleation and growth mode of Zn deposition changed from a three-dimensional progressive nucleation to three-dimensional instantaneous nucleation in the presence of Cu(I) ions. The addition of Cu(I) ions was observed to change the surface morphology, purity, and crystallographic orientation of the zinc deposits.

Optical monitoring of the electrochemical nucleation and growth of silver nanoparticles on electrode: From single to ensemble nanoparticles inspection

The electrochemical nucleation and growth of nanoparticles (NPs) on an electrode surface at a constant potential is traditionally followed by recording the resulting current density during the experiment. The obtained chronoamperometric transients are average measurements, making it difficult to separate individual NP behaviors and to study their cross-talks. Herein, the recently developed Backside Absorbing Layer Microscopy (BALM) is employed to monitor optically in situ and operando the electrodeposition of silver NPs. This latter technique exploits a pseudo-antireflective and metallic contrast layer and allows both sub-nanometer vertical and sub-micrometer spatial resolutions. The information from the recorded movies is readily exploited to study the NP electrodeposition at the single entity level. The image sequences allow quantifying the local electrodeposition of nanomaterials onto the electrode surface, probing the NP dynamics through the extraction of single optical NP growth transients, and analyzing the effect of the neighboring nuclei on the growth of individual NPs.

Sulphur-induced electrochemical synthesis of manganese nanoflakes from choline chloride/ethylene glycol-based deep eutectic solvent

Deep eutectic solvents with the advantages of being less expensive, non-toxic, renewable, and biodegradable are emerging as versatile solvent systems for the electrochemical synthesis of advanced functional materials. Herein, we study the electrochemical deposition of Mn nanoflake arrays grown on Cu foam and the morphology evolution of Mn crystals in the early stages of nucleation and growth in a choline chloride/ethylene glycol-based deep eutectic solvent (Ethaline-based DES). Thiourea (TU) is an efficient additive that is found to promote the electrochemical reduction of Mn(II) species in Ethaline-based DES and induce the formation of Mn nanoflake architectures with a nanoporous configuration. Investigation of the nucleation and growth processes with chronoamperometric transients reveals that the presence of TU can accelerate the generation of homogeneous Mn nuclei and dramatically enhanced the nucleation rate by modifying the corresponding nucleation and growth model from 3D progressive to 3D instantaneous. TU is found to play an important role in the crystallization kinetics of Mn crystals and manipulate the shapes, sizes, and growth morphologies of the formed Mn films. Our work highlights the importance of additives for controlling the microtopography of nanostructured Mn in Ethaline-based DES for potential electrochemical applications.

Proton Sensitive Additive for Cobalt Electrodeposition

Cobalt electrodeposition involves hydrogen reduction reaction, and the proton supply in feature filling varies depending on the location because of the topographical characteristics, thereby resulting in changes on the electrode surface, such as changes in pH and hydrogen adsorption. Based on this phenomenon, void-free trench filling was performed using benzimidazole (BZI) as an additive, which has different suppression effects depending on pH. Linear sweep voltammetry experiments confirmed the change in suppression behavior of the additive according to pH. Chronoamperometric transients were performed at a fixed BZI concentration to confirm the potential region, wherein actual cobalt deposition was suppressed. Chronoamperometric analysis with various rotation rates was also conducted to demonstrate the effect of proton concentration near the electrode on the suppression effect of BZI. Finally, a void-free filling working mechanism in a low aspect ratio trench using BZI was proposed. This study proposes, a single additive, whose suppression behavior changes according to the change in pH of the electrode surface, by considering the pH of the cobalt deposition solution and pKa value of the additive. Furthermore, it was demonstrated that void-free filling can be performed even in a trench with a low aspect ratio.

Kinetic Monte Carlo applied to the electrochemical study of the Li-ion graphite system

To delve deeper into the kinetics involved in the staging phenomena of lithium insertion into graphite, it is necessary to develop theoretical models that emulate the physical phenomenon involved. In the present work kinetic Monte Carlo simulations are used to carry out a thorough analysis of the Li-ion graphite system, with the twofold aim of providing atomistic support for interpretations based on several experimental electrochemical techniques commonly used in the laboratory and of making theoretical predictions for future experimental work. Cyclic voltammograms and chronoamperometric transients are obtained, and diffusion coefficients and exchange current densities are calculated at different Li loadings of graphite. These results are compared with selected experimental data from the literature. In this way, there emerge details that cannot be observed in ordinary experiments due to methodological/instrumental limitations. For example, it is found that chronoamperometric responses are different for intercalation and deintercalation, the latter being a faster process. The reason why these phenomena are different is revealed, supporting and widening experimental assumptions. The present results also suggest that the intrinsic hysteresis observed in experimental work (and in simulations) is due to kinetic factors.

Bottom-up Filling of Damascene Trenches with Gold in a Sulfite Electrolyte

Superconformal Au deposition is demonstrated in a Na3Au(SO3)2 + Na2SO3 electrolyte using Bi species to catalyze the reduction of Au(SO3)23−. Micromolar additions of Bi3+ to the sulfite-based electrolyte accelerate the reduction of Au(SO3)23− as shown by hysteretic voltammetry and rising chronoamperometric transients. Superconformal feature filling is observed over a defined range of Bi3+ concentration, potential and hydrodynamics. Over a more limited parameter range, approximately −0.9 V to −0.95 V, void-free, bottom-up filling of Damascene trenches is achieved. Furthermore, in the presence of significant convection the bottom-up filling is accompanied by passivation of the free surface. Bottom-up feature filling is characterized by a counterintuitive dependence of the free surface reactivity on the available flux of the Bi3+ accelerator species suggestive of an unusual coupling between hydrodynamic transport, shear and interfacial chemistry.

Study of Chronoamperometric Transients Obtained from Stainless Steel A304 in a Solution Type NACE TM 0177

Stainless steel is one of the most important materials, because its composition provides it corrosion resistance property, so this material it is known like a multipropose material. That is why A304 stainless steel is the most useful steel in chemical industry. At present, few authors have been interested in the study of corrosion with purpose of using it as a method of obtaining electrochemically active surfaces for technological purposes. In the present work, the results of the study of the energetic conditions for controlled pit production in stainless steel A304 are shown. The study was carried out using corrosive medium rich in chlorides like solution type NACE TM 0177. A flat three-electrode electrochemical cell was assembled using A304 stainless steel samples as working electrodes, saturated calomel (SCE) as reference electrode and a graphite bar as auxiliary electrode. This cell was coupled to a potentiostat-galvanostat GAMRY EIS 300 to perform Potentiodynamic Polarization in from OCP to 0.5 V. From the obtained results there were selected four different potentials for chronoamperometric transients study, which were performed using the electrochemical flat cell coupled to a potenctiostat-galvanostat and Zero Resistance Ammeter ACM Gill AC, at four different time laps. The obtained surface after the experiments was characterized with Scanning Electron Microscopy (SEM) to analyze the pits characteristics morphology and size.

Electrochemical Reduction of 2,4-Dinitrotoluene in Room Temperature Ionic Liquids: A Mechanistic Investigation

The reduction mechanism of 2,4-dinitrotoluene (DNT) has been studied in eight room temperature ionic liquids (RTILs) using cyclic voltammetry (CV), square wave voltammetry (SWV), chronoamperometry, and digital simulation. Two distinctive peaks are observed in the voltammetry, corresponding to the stepwise reduction of the two nitro groups on the aromatic ring. Diffusion coefficients (D) and electron counts (n) were calculated from chronoamperometric transients, revealing an electron count of one in most RTILs, and a linear relationship between D and the inverse of viscosity. Focusing on the first reduction only, the peak appears to be chemically reversible at low concentrations. However, as the concentration increases, the current of the reverse peak diminishes, suggesting that one or more chemical steps occur after the electrochemical step. The results from digital simulation of the CVs in one of the RTILs reveal that the most likely mechanism involves a deprotonation of the methyl group of a parent DNT molecule by the electrogenerated radical anion and/or a dimerisation of two electrogenerated radical anions. Elucidation of the reduction mechanism of DNT (and other explosives) is vital if electrochemical techniques are to be employed to detect these types of compounds in the field.

Electrochemical preparation of Ni-La alloys from the EMIC-EG eutectic-based ionic liquid

The electrodeposition behavior of Ni-La alloys was investigated in 1-ethyl-3-methylimidazolium chloride-ethylene glycol (EMIC-EG; 1:2-M ratio) eutectic-based ionic liquid containing 0.1 M NiCl2 and 0.2 M LaCl3. Cyclic voltammograms revealed that La could be co-deposited with Ni under the inducement of Ni(II) species in this solvent. The analysis of the chronoamperometric transients showed that, as with deposition of metal Ni, the co-deposition of Ni-La alloy on a glassy carbon electrode followed an instantaneous nucleation and three-dimensional growth controlled by diffusion. Galvanostatically deposited Ni-La alloys with different composition and morphology were characterized by inductively coupled plasma–atomic emission spectrometry (ICP-AES), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM). The current density and temperature were found to play an important role in controlling the composition and surface morphology of the resultant Ni-La alloys. The structure of these deposits depended on the La content. Alloys containing less than 4 at.% La could be indexed to a disordered face-centered cubic structure similar to pure Ni, whereas alloys containing about 9 at.% Ni were completely amorphous (metallic glass).

The Effect of Temperature on Kinetics and Diffusion Coefficients of Metallocene Derivatives in Polyol-Based Deep Eutectic Solvents.

The temperature dependence of the density, dynamic viscosity and ionic conductivity of several deep eutectic solvents (DESs) containing ammonium-based salts and hydrogen bond donvnors (polyol type) are investigated. The temperature-dependent electrolyte viscosity as a function of molar conductivity is correlated by means of Walden’s rule. The oxidation of ferrocene (Fc/Fc+) and reduction of cobaltocenium (Cc+/Cc) at different temperatures are studied by cyclic voltammetry and potential-step chronoamperometry in DESs. For most DESs, chronoamperometric transients are demonstrated to fit an Arrhenius-type relation to give activation energies for the diffusion of redox couples at different temperatures. The temperature dependence of the measured conductivities of DES1 and DES2 are better correlated with the Vogel-Tamman-Fulcher equation. The kinetics of the Fc/Fc+ and Cc+/Cc electrochemical systems have been investigated over a temperature range from 298 to 338 K. The heterogeneous electron transfer rate constant is then calculated at different temperatures by means of a logarithmic analysis. The glycerol-based DES (DES5) appears suitable for further testing in electrochemical energy storage devices.

Methyl salicylate detection via electrochemical transients using nano spinel Co3O4 films

The mixed nano spinel Co3O4 films were fabricated through electrochemical deposition followed by peroxide oxidation and heat treatment. Electrochemical characteristics of the deposition and textural as well as morphological characteristics of the films were analyzed. Both 400 plane for Co3O4 and the 200 plane for CoO were noted. Based on IR studies, hydroxides decomposed into oxides on annealing. Oxide films are having the stoichiometric atomic weight ratio, O:Co as 1:2.7. Chronopotentiometric and chronoamperometric transients were recorded for the anodic oxidation of methyl salicylate using cobalt oxide films. Based on the electrochemical kinetic data, oxidation mechanism scheme is proposed and the net oxidation rate depends on sluggish charge-transfer limitations. Salicylate di-ion to 1, 2 benzoquinone is more favorable than 1, 4 benzoquinone derivative with four-electron transfer, whereas methoxide to formaldehyde involves two-electron transfer.

On the activation energy of the formic acid oxidation reaction on platinum electrodes

A temperature dependent study on the formic acid oxidation reaction has been carried out in order to determine the activation energy of this reaction on different platinum single crystal electrodes, namely Pt(100), Pt(111), Pt(554) and Pt(544) surfaces. The chronoamperometric transients obtained with pulsed voltammetry have been analyzed to determine the current densities through the active intermediate and the CO formation rate. From the temperature dependency of those parameters, the activation energy for the direct reaction and the CO formation step have been calculated. For the active intermediate path, the activation energy are in the range of 50–60kJ/mol. On the other hand, a large dependence on the electrode potential is found for the activation energy of the CO formation reaction on the Pt(100) electrode, and the activation energy values for this process range between 20 and 100kJ/mol. These results have been explained using a reaction mechanism in which the oxidation of formic acid requires the presence of a pre-adsorbed anion on the electrode surface.

Direct chronoamperometric determination of free available chlorine in soil samples using built-in diffusion layer coated glassy carbon electrode

In this work, a glassy carbon electrode supplied with a built-in diffusion layer and a short-time chronoamperometric method were used for obtaining reliable concentration values from I–t curves recorded in tortuous media. It was proved that short-time chronoamperometric transients taken with the modified electrode in tortuous matrices can be evaluated using calibrating data recorded in simple aqueous standards. The applicability of the in situ analytical method was tested for determination of active chlorine concentration in different bleaching powder treated soil samples. Iodometric titrations were employed for comparison. The results prove that residual concentration of active chlorine can be estimated with 0.66 % relative standard deviation using the proposed in situ chronoamperometric measuring methods in humid soil slurry after bleaching powder disinfection.

Influence of Additive on Morphology and Nucleation Mechanism for Zn-Electrodeposition

In this study, the influence of sodium dodecylbenzenesulfonate (SDBS) as additive on the morphology and nucleation mechanism for zinc electrodeposition on steel sheet was investigated using scanning electron microscopy (SEM) and potentiostatic electrochemical techniques. From the analysis of the chronoamperometric transients and the SEM images, an instantaneous nucleation with 3D growth has been proposed in both baths with and without SDBS. It was found that the morphology of zinc electrodeposits varied from initial thin-layered hexagonal plates to a finer ridge and needle morphologies with increasing the overpotential as SDBS was added in the bath solution.

Superconformal Cu Electrodeposition from Cu(II)-EDTA Complexed Alkaline Electrolyte

This paper details superconformal filling of submicrometer trenches with bright, dense copper from alkaline cupric ethylenediaminetetraacetic acid (EDTA) electrolyte of pH 12. Enhanced deposition from the bottom corners of the trenches and overfill bumps accompany superconformal deposition within the trenches when micromolar concentrations of KSeCN are added. Cyclic voltammograms using a rotating disk electrode (RDE) indicate that metal deposition from the EDTA complexed electrolyte is kinetically hindered. The SeCN− additive induces positive feedback evident as concentration-dependent depolarization in cyclic voltammograms and rising chronoamperometric transients. The feature filling and electrochemical measurements are discussed in the context of existing models for superconformal feature filling.

Voltammetric concentration measurements in diffusion-hindered media

In voltammetric analysis the signal—in most cases—depends on transport processes. When getting concentration values of analytes from voltammetric calibrating curves, it is expected that the mass transport characteristics in sample solutions and in calibrating standards are identical. Standard addition methods are used in analytical practice when making calibrating standard with transport properties matching that of the samples would be difficult. Voltammetric measurements can also be carried out in soil—in sediment—or in gel samples. The mass transport conditions in these media, however, can considerably differ from those existing in aqueous solutions. The application of standard addition technique, however, is not an option there. In this work, a glassy carbon electrode was applied with a built-in diffusion layer on its measuring surface and chronoamperometric measurements were carried out. The current–time transients taken in aqueous solution and in tortuous, diffusion-hindered media were compared. Ascorbic acid and iodine as analytes as well as silica sand sediments and green pepper pulps as tortuous matrices were used. It was proved that if the modified electrode is used for analysis, then short time chronoamperometric transients taken in tortuous media can be evaluated by calibration data taken in aqueous standard solutions.

Superfilling Damascene Trenches with Gold in a Sulfite Electrolyte

Superconformal Au deposition is demonstrated in a Na3Au(SO3)2 - Na2SO3 based electrolyte using underpotential deposited (upd) Pb to catalyze the reduction of Au(SO3)23−. Micromolar additions of Pb2+ to the electrolyte give rise to acceleration of the Au deposition rate as evidenced by hysteretic voltammetry and rising chronoamperometric transients that convolve the diffusion, adsorption kinetics and coverage isotherm of the upd Pb catalyst. The catalytic activity on the Au deposition reaction may be quenched, or reset, by stepping the potential to more positive values to deactivate or strip the Pb catalyst. Void-free Damascene trench superfilling at various fixed potentials and Pb2+ concentrations is demonstrated and shown to be congruent with the curvature enhanced accelerator model (CEAC) of superconformal growth. This includes enhanced deposition due to catalyst enrichment on concave surface segments at the bottom corners of the trenches, followed by rapid bottom-up growth and, for certain conditions, bump formation above the filled trenches.

Analysis of Pit Stability in Type 316L Stainless Steel Exposed to H2S-Saturated Dilute Chloride Solutions Above the Critical Pitting Temperature

Abstract This study examines the effect of hydrogen sulfide (H2S) on the transition from metastable to stable propagating pits using Type 316L (UNS S31603) steel in brines with Cl− concentrations of 10−3 M to 2 × 10−2 M at 75°C and 150°C. The potentiostatic tests were performed at discrete intervals of 50 mV from the recorded open-circuit potential (OCP) to 300 mV above the OCP. The results based on analysis of the chrono-amperometric transients suggests that the transition to stable pit growth is hindered by H2S saturation at both temperatures. The comparison of the experimental results with similar tests in an acidified control brine (without H2S saturation) indicates that the effect of H2S in the promotion of pit metastability is associated with the diffusion of H2S to the bottom of the cavity. This increases the net anodic current by irreversibly forming metallic sulfides, which, in turn, affect the pit's anolyte by reducing the metal salt concentration. The consequence of this effect is that small pi...