Electrodissolution Of Copper Research Articles

Dynamic Electrolyte Spreading during Meniscus-Confined Electrodeposition and Electrodissolution of Copper for Surface Patterning.

Meniscus-confined electrodeposition and electrodissolution are a facile maskless approach to generate controlled surface patterns and 3D microstructures. In these processes, the solid-liquid interfacial area confined by the meniscus dictates the zone on which the electrodeposition or the electrodissolution occurs. In this work, we show that the process of electrodeposition or electrodissolution in a meniscus-confined droplet system can lead to dynamic spreading of the meniscus, thereby changing the solid-liquid interfacial area confined by the meniscus. Our results show that the wetting dynamics depends on the applied voltage and the type of interface underneath the droplet, specifically a smooth surface with a homogeneous solid-liquid interface or a superhydrophobic surface with a heterogeneous solid-liquid and liquid-vapor interface. It is found that both electrodissolution and electrodeposition processes induced droplet spreading in the case of a smooth surface with a homogeneous interface. However, a superhydrophobic surface with a heterogeneous interface under the droplet produced nonlinear spreading during electrodissolution and spreading inhibition during electrodeposition. The underlying mechanisms resulting in the observed behavior have been explicated. The dynamic droplet spreading could modify the dimensions of the patterns formed and hence is of immense importance to the meniscus-confined electrochemical micromachining. The findings also provide fundamental insights into the spreading behavior and wetting transitions induced by electrochemical reactions.

Bifurcation analysis for Shil'nikov Chaos Electro-dissolution of Copper.

This paper is devoted to study the local bifurcations and stability of three dimensional systems that representing a Shil'nikov chaos during copper electro-dissolution. The local stability analysis of equilibrium points has been studied. It is shown that transcritical bifurcation can appears in the system. Also, the existence of Hopf bifurcation of the system around the equilibrium points is studied when the parameter passes through the critical value. Normal form theory is used to study bifurcating periodic solutions.

Operando Synthesis of High-Curvature Copper Thin Films for CO₂ Electroreduction.

As the sole metal that could reduce CO2 to substantial amounts of hydrocarbons, Cu plays an important role in electrochemical CO2 reduction, despite its low energy efficiency. Surface morphology modification is an effective method to improve its reaction activity and selectivity. Different from the pretreated modification method, in which the catalysts self-reconstruction process was ignored, we present operando synthesis by simultaneous electro-dissolution and electro-redeposition of copper during the CO2 electroreduction process. Through controlling the cathodic potential and CO2 flow rate, various high-curvature morphologies including microclusters, microspheres, nanoneedles, and nanowhiskers have been obtained, for which the real-time activity and product distribution is analyzed. The best CO2 electro-reduction activity and favored C2H4 generation activity, with around 10% faradic efficiency, can be realized through extensively distributed copper nanowhiskers synthesized under 40 mL/min flow rate and −2.1 V potential.

Quantitative, In Situ Visualization of Metal-Ion Dissolution and Transport Using (1) H Magnetic Resonance Imaging.

Quantitative mapping of metal ions freely diffusing in solution is important across a diverse range of disciplines and is particularly significant for dissolution processes in batteries, metal corrosion, and electroplating/polishing of manufactured components. However, most current techniques are invasive, requiring sample extraction, insertion of an electrode, application of an electric potential or the inclusion of a molecular sensor. Thus, there is a need for techniques to visualize the distribution of metal ions non‐invasively, in situ, quantitatively, in three dimensions (3D) and in real time. Here we have used 1H magnetic resonance imaging (MRI) to make quantitative 3D maps showing evolution of the distribution of Cu2+ ions, not directly visible by MRI, during the electrodissolution of copper, with high sensitivity and spatial resolution. The images are sensitive to the speciation of copper, the depletion of dissolved O2 in the electrolyte and show the dissolution of Cu2+ ions is not uniform across the anode.

Quantitative, In Situ Visualization of Metal‐Ion Dissolution and Transport Using 1H Magnetic Resonance Imaging

AbstractQuantitative mapping of metal ions freely diffusing in solution is important across a diverse range of disciplines and is particularly significant for dissolution processes in batteries, metal corrosion, and electroplating/polishing of manufactured components. However, most current techniques are invasive, requiring sample extraction, insertion of an electrode, application of an electric potential or the inclusion of a molecular sensor. Thus, there is a need for techniques to visualize the distribution of metal ions non‐invasively, in situ, quantitatively, in three dimensions (3D) and in real time. Here we have used 1H magnetic resonance imaging (MRI) to make quantitative 3D maps showing evolution of the distribution of Cu2+ ions, not directly visible by MRI, during the electrodissolution of copper, with high sensitivity and spatial resolution. The images are sensitive to the speciation of copper, the depletion of dissolved O2 in the electrolyte and show the dissolution of Cu2+ ions is not uniform across the anode.

Delayed feedback induced multirhythmicity in the oscillatory electrodissolution of copper.

Occurrence of bi- and trirhythmicities (coexistence of two or three stable limit cycles, respectively, with distinctly different periods) has been studied experimentally by applying delayed feedback control to the copper-phosphoric acid electrochemical system oscillating close to a Hopf bifurcation point under potentiostatic condition. The oscillating electrode potential is delayed by τ and the difference between the present and delayed values is fed back to the circuit potential with a feedback gain K. The experiments were performed by determining the period of current oscillations T as a function of (both increasing and decreasing) τ at several fixed values of K. With small delay times, the period exhibits a sinusoidal type dependence on τ. However, with relatively large delays (typically τ ≫ T) for each feedback gain K, there exists a critical delay τcrit above which birhythmicity emerges. The experiments show that for weak feedback, Kτcrit is approximately constant. At very large delays, the dynamics becomes even more complex, and trirhythmicity could be observed. Results of numerical simulations based on a general kinetic model for metal electrodissolution were consistent with the experimental observations. The experimental and numerical results are also interpreted by using a phase model; the model parameters can be obtained from experimental data measured at small delay times. Analytical solutions to the phase model quantitatively predict the parameter regions for the appearance of birhythmicity in the experiments, and explain the almost constant value of Kτcrit for weak feedback.

Periodic and complex waveform current oscillations of copper electrodissolution in phosphoric acid in an epoxy-based microchip flow cell

We investigate the dynamical behavior of anodic copper dissolution in phosphoric acid in an on-chip integrated microfluidic flow cell. Electrodissolution of copper in the microcell displayed periodic, smooth, and relaxation oscillations. The system displayed complex waveforms with mixed-mode and chaotic oscillations as well. These waveforms appeared when proper external resistance, flow rate, and circuit potential were applied. The oscillations in the Cu-phosphoric acid system exhibited a strong dependence on the flow rate of the electrolyte solution. An increase in flow rate correlated with a decrease in the minimum external resistance required for oscillations. The experiments displayed a considerable “drift” where repeated linear polarization scan measurements resulted in a decrease of current level as well as a shift of the range of oscillations to lower (more negative) potentials. The experiments also indicated that the direction of flow affected the observed dynamics of the microcell flow system. Pushing the flow moved the acid through the channel over the recessed Cu electrode to reservoir accommodating the counter and reference electrode; pulling the flow transferred the acid from the reservoir to the electrode. With pull flow, an increased oscillatory potential range and a greater variety of complex waveform types were observed.

Chaos Induction Using a Reference Model Assisted Control

A stable period two orbit in the parametric vicinity of a chaotic attractor is prevented from being reached, via the exclusion of trajectories from its near vicinity using a reference model based control strategy. This results in the inception of sustained chaotic dynamics. The reference model control strategy includes a predictive term enabling delimitation of precluded zones for the system dynamics. This technique for promotion of chaotic behavior is illustrated by using an experimental electrochemical cell involving the potentiostatic electro-dissolution of copper in phosphoric acid.

ChemInform Abstract: The Anodic Dissolution of Copper in Hydrochloric Acid Solutions.

The electrodissolution of copper in hydrochloric acid solutions at the rotating ring-disk elec- trode was found to be controlled by both mass transfer and reaction in the apparent-Tafel region in HCl concentrations of between 0.1 and 1.0 M. The proposed mechanism describes the adsorption of CuCl, on the corroding copper surface and the diffusion of CuCl; from the copper surface. The reaction in the limiting-current region was found to be controlled by the diffusion of Cl- to the copper surface through a porous CuCl layer that forms on the surface. The thickness of this porous layer is dependent on the stirring conditions, and independent of the Cl- concentration. Cu'+ is also produced at the Cu surface during electrodissolution. A mechanism describing the formation of a porous film of CuCl on the surface, the diffusion of Cl- through this tilm and the formation of Cu*+ has been proposed.

Electrochemical resonance: Frequency response analysis of the electrodissolution of copper in trifluoroacetic acid close to dynamic instabilities

In the present work the frequency response of the electrochemical interface is investigated during the electrodissolution of copper in trifluoroacetic acid (TFA). The instability of a stable steady state to periodic oscillations is characterized and thus the nature of the steady state close to the instability is revealed to be a stable focus. The frequency response of the stable focus is explored by electrochemical impedance spectroscopy and the impedance amplitude profile (ZAP) method. It is shown that the system resonates at a specific frequency of the input signal and thus acts as a resonator (band-pass filter) similarly to neural resonators.

Copper corrosion and anodic electrodissolution mechanisms in naturally aerated stagnant 0.5 M [formula omitted

Mechanisms of copper corrosion and electrodissolution in naturally aerated, stagnant 0.5 M H 2 SO 4 were investigated by means of electrochemical techniques, compared with deaerated measurements. The role of dissolved oxygen was suggested, and three models were proposed in - 0.05 ∼ 0.15 V vs. SCE range. Near to corrosion potential, chemical redox between cuprous intermediate and oxygen reduction reaction (ORR) intermediate accelerated copper corrosion, and corrosion rate was controlled by a combined cathodic kinetic–anodic diffusion process. In low and high potential ranges, chemical redox, occurred between cuprous intermediate and oxygen molecule, synergistically accelerated the electrodissolution of copper.

SERS and EQCM studies on the effect of allyl thiourea on copper dissolution and deposition in aqueous sulfuric acid

We investigated the effect of allyl thiourea (ATU) on both the electrodeposition and electrodissolution of copper in aqueous sulfuric acid by combining cyclic voltammetry (CV) with electrochemical quartz crystal microbalance (EQCM) studies and surface enhanced Raman spectroscopy (SERS). The results demonstrated that the two-electron transfer reaction is the predominant process for the copper dissolution–deposition process in 1.0 M H2SO4 solution not containing ATU in the potential range −0.65 to 0.05 V versus SCE. In comparison, the copper dissolution–deposition process in 1.0 M H2SO4 solution containing ATU corresponds to a one-electron transfer reaction. The spectral features observed from the SERS studies showed at molecular level that ATU can be adsorbed tilted to the copper electrode surface and that coordination occurs via the sulfur atom. The secondary amino group is nearer to the surface than the primary amino group. SO 4 2− and HSO 4 − can be coadsorbed on the protonated −NH (CH2CHCH2) groups.

Analysis of current transients for voltage pulse-modulated surface processing: Application to anodic electro-dissolution of copper for electrochemical mechanical planarization

The voltage pulse modulation technique is useful for electrochemical processing of metal and alloy surfaces by utilizing faradaic reactions like electro-deposition and electro-dissolution. A theoretical framework is presented here to facilitate quantitative analysis of experimental data (current transients) obtained in this approach. A typical application of this analysis is demonstrated for an experimental system involving electrochemical removal of copper surface layers, a relatively new process for abrasive-free electrochemical mechanical planarization of copper lines used in the fabrication of integrated circuits. Voltage pulse-modulated electro-dissolution of Cu in the absence of mechanical polishing is activated in an acidic solution of oxalic acid and hydrogen peroxide. The current generated by each applied voltage step shows a sharp spike, followed by a double-exponential decay, and eventually attains the rectangular shape of the potential pulses. The formulas presented here show excellent fits to these current transients, and help to probe the detailed electrochemistry of surface layer removal using a simple circuit model of the reactive interface.

Electrochemical generation of Cu(I) complexes in aqueous solutions studied by on-line mass spectrometry

Taking advantage of the electrochemical aspects of electrospray ionization (ESI) sources in positive ionization mode mass spectrometry (MS), aqueous copper complexes are electrogenerated using sacrificial copper electrodes. When using 8-hydroxyquinoline or bathocuproine, two chelating agents for Cu 2+ and Cu + ions, respectively, the electrodissolution of copper leads to the formation of the respective complexes that are then analyzed by MS. This electrochemical generation of copper(I) complexes offers a direct route to synthesize Cu + complexes in aqueous solutions.

Current Oscillations in Anodic Electrodissolution of Copper in Lithium-ion Battery Electrolyte

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Current oscillations in anodic electrodissolution of copper in lithium-ion battery electrolyte

Current oscillations were observed during electrodissolution of copper in nonaqueous lithium-ion battery electrolyte under potentiostatic conditions using copper foil electrodes. Mixed-mode oscillations were observed over certain ranges of stir rate and applied potential. A nonlinear dynamics technique (return map) was applied to characterize the oscillations. The dynamic stir conditions of the electrolyte influenced the frequency and pattern of the oscillations. The amplitude of the oscillations increased with increasing potential. Also, cyclic voltammetry (CV) showed that the oscillatory current was correlated to the oxidation of the copper electrode.

Application of the impedance model of de Levie for the characterization of porous electrodes

From the de Levie's theory for a porous electrode, the impedance can be expressed in function of the cylindrical pore characteristics: the pore length, the pore radius and the number of pores. If the pores have a finite length, these parameters can be regressed from the experimental impedance diagrams. In the case of a semi-infinite pore length, only the product r 3/2 n can be obtained. In this paper, two practical examples of porous electrodes were presented: the corrosion of cast iron in drinking water and the electrodissolution of copper in 1 M hydrochloric acid solution. In each case, the pore parameters were assessed.

Birhythmicity induced by perturbing an oscillating electrochemical system.

We describe the generation of new limit cycles in electrochemical systems under the influence of external periodic perturbations. For certain specific parameters of a nonharmonic forcing function, two coexisting periodic orbits can be generated from a single limit cycle observed in the unperturbed dynamics. This inception of birhythmicity (bistability) is observed in both simulations and actual experiments involving potentiostatic electrodissolution of copper in an acetate buffer.

OSCILLATORY BEHAVIOR AS ELECTROCHEMICAL FLUCTUATIONS DURING THE TRANSPASSIVE ELECTRODISSOLUTION OF COPPER IN PHOSPHORIC ACID

Transpassive electrodissolution of copper in phosphoric acid was studied froma dynamical point of view. A new electrochemical oscillation named corrosion oscillation as the form of electrochemical noise appears at the corrosion region. The pre-passivated copper electrode in phosphoric acid media shows a fluctuated current within the active potential region. The current oscillation in this system, and generally in electrochemical systems, is sensitive to the initial condition of the electrode surface from heterogeneity point of view. We show that the noise in the current-potential curve is caused by a tiny instability of the passive film, a transition from the passive to extrapassive states and vice versa. Here we demonstrate that the current oscillations can also be observed in the low scale of electrochemical noise. Moreover, the possible mechanism for the electrochemical noise and generally the other noises are also described. The study is of interest from an interdisciplinary point of view as shown by complicated processes such as noises, can be recognized in a dynamical system by applying a closer view in a lower scale. Thus, it is a typical (but not general) study for investigation and monitoring tiny processes in scale, whereas they are so complicated.

Anodisation of copper in thiourea-containing acid solution

Abstract The formation of anodic films during the anodisation of copper, at different applied potentials E, in aqueous 0.5 M sulphuric acid containing different amounts of dissolved thiourea was investigated following the corroding electrode profile by on line in situ imaging. For E 0.07 V, the main reactions are the electro-decomposition of formamidine disulphide and Cu(I)–thiourea complexes yielding a copper sulphide-containing film (film II) and the electrodissolution of copper as aqueous Cu(II) ions through film II. The relative contribution of these processes depends on thiourea concentration in the solution, the applied electric potential and anodisation time. The growth kinetics of films I and II were determined from the evolution of the average film height 〈h〉 obtained from in situ imaging. The kinetics of film I fit a parabolic rate law, whereas those of film II approach a linear 〈h〉 versus anodisation time relationship. The rupture of film II assists the localised corrosion of copper. Likely physical mechanisms for the formation of these anodic films are discussed.