Electrochemical Metal Deposition Research Articles

Осаждение металлов в пористую структуру оксида алюминия

Introduction. Nanostructured porous anodic aluminum oxide is used as a matrix, where it is often necessary to introduce impurities of various metals into its structure. In this case, an effective solution is the electrochemical deposition of metals into the pores of anodic aluminum oxide. However, metals can be deposited on the cathode from aqueous solutions of salts in which the electrode potential is electronegative and less than the potential for hydrogen evolution in solutions. Materials and methods. The anodizing process takes place in two stages: preliminary anodizing and anodizing itself. Before preliminary anodization, experimental samples were coated with a chemically resistant varnish for separation between the electrolyte and air. Then the samples prepared in this way were dried for 4–6 hours, after which the second stage of anodization was carried out. Results. It has been revealed that substrate inhomogeneities can be reduced by slowing down the oxide growth process or by using pore blanks. Using similar methods, a highly ordered structure can be achieved. A more dense arrangement of pores can be achieved through the use of strong acids, forming a barrier layer of thinner thickness with more penetration paths. It is worth noting that when using such acids, the number of inhomogeneities becomes not such an important parameter. Discussion. Films were obtained with greater chemical strength and a thickness of 84-100 microns, a pore diameter of 0.15-0.3 microns. By carrying out additional etching, the pore diameter was increased to 0.6 µm. Etching of PHA can be carried out in an alkali solution in an anhydrous solution of ethyl alcohol. Also, pores can be dissolved by reanodizing in a solution of phosphoric acid. The barrier layer grows to 100 A, removal is carried out with dilute hydrofluoric acid. The resulting PHAs have a fairly porous, homogeneous structure with an average effective pore size of 0.45-0.65 μm. Conclusion. Conditions have been developed for the joint deposition of two metals from aqueous solutions at close values of their electrode potentials, such as iron and cobalt. The conditions for the deposition of copper from copper sulfate into the pores of porous aluminum oxide have been established at 25 – 70 t/l of sulfate and 7÷12% sulfuric acid. Resume. The research results can be useful in obtaining films of porous anodic aluminum oxide, which can be used as substrates for creating solar-electric energy converters based on materials with a perovskite structure. This is especially true for the Republic of North Ossetia-Alania and for the mountainous territories of the North Caucasus. The use of solar energy converters will make it possible to more efficiently electrify populated areas in mountainous areas.

(Invited) Ultrafast Electrodeposition of Faceted Li Metal

Electrochemical deposition of metals with precise morphological and chemical control is of fundamental importance to a broad range of electrochemical systems, including energy storage, large scale manufacturing, electronics, and electrocatalysis. For non-reactive metals (e.g. Ni, Pt), electroplating is a commercially established process that gives the desired control of deposition morphology and chemistry. However, deposition of reactive metals (e.g. Li, Na) critical for enabling next-generation batteries is complicated by metal surface corrosion that occurs concurrently with metal deposition, making such electrodeposition processes neither well-understood nor well-controlled. This work highlights the electrodeposition of lithium (Li), a reactive metal anode plagued with uncontrolled dendritic morphologies and surface corrosion, both of which are intimately linked and occur simultaneously. Despite tremendous research efforts to mitigate these issues, common literature descriptions of Li metal deposits (e.g. “chunky”, “pancake”) and their corrosion films (e.g. “strong”, “stable”) are ill-defined and often qualitative, highlighting our incomplete understanding of the deposition process and hindering the practical application of high energy battery chemistries enabled by Li metal. Our work seeks to bridge this critical gap in understanding by solving the fundamental challenge of (1) decoupling simultaneous electrodeposition from surface corrosion of reactive metals and (2) observing their reactive nanoscale interface.

Surface Diffusion on Ag(100) and Cu(100) Electrodes in the Presence of Low Coverage Halides

Atomic-scale processes at the electrochemical interface are of great importance to not only the fundamental research of electrochemistry, but also the newly developing technologies including energy conversion and bottom-up nanofabrication. In particular, the surface-active additive, such as halides, can strongly affect these processes, hence change the micro or macro behaviors of the studied system. For example, adding halides to the electrolyte is a feasible way to change the shape of the synthesized nanoparticles [1]. Besides, the modification of catalytic activity and selectivity by halide-containing electrolyte in CO2 electrochemical reduction on Cu surface has also been reported [2]. Therefore, a detailed and quantitative study of the electrochemical interface processes in the presence of co-adsorbed halides species may pave the way for more efficient design of electrochemistry-related procedures. Surface diffusion of adsorbates on the electrode is one of these processes, playing an important role e.g. in electrocatalysis, and electrochemical metal deposition or dissolution. Video-rate scanning tunneling microscope (Video-STM) in an electrochemical environment enables the recording of real-time videos of atomic-scale motion on electrode surfaces, which makes the observation and quantification of surface diffusion of individual adsorbed atoms and molecules possible [3].Halides form strongly adsorbed c(2x2) structures on various metal surfaces at the positive end of the double layer range. Our previous studies revealed a significant potential dependence of the surface diffusion of sulfur on Cu(100) and Ag(100) electrodes in the presence of close-packed c(2x2) halide adlayers [3,4]. In this range, sulfur atoms diffuse by hopping between neighboring sites of the c(2x2) lattice. The mobility of the atoms exponentially decreases with increasing potential, following a linear relationship between the potential and the diffusion barrier. More specifically, for a given system, the change of the diffusion barrier with the potential can be attributed to the change in the surface dipole moment along the diffusion path. Further studies demonstrated that the potential-dependence is independent of the diffusing species, which means that the co-adsorbed halides may dominate the change of the dipole moment.Here, instead of the c(2x2) potential range, the surface diffusion is studied in the negative potential range of Br-covered Ag(100), where Br forms a highly mobile lattice gas on the surface and the coverage increases with potential. Sulfur diffusion via hopping between neighboring sites of the (1x1) Ag substrate lattice was observed. Surprisingly, the diffusion rates increase with increasing potential, suggesting a different diffusion mechanism in the presence of low coverage halides. However, there is a wide potential gap between (1x1) and c(2x2) range, where quantitative Video-STM studies are difficult due to the high mobility of sulfur atoms at room temperature. Therefore, we also collected diffusion data at low temperature, which show the same potential dependence as the room temperature data, apart from a reduced mobility. These experiments allowed to show that the crossover between increasing and decreasing diffusion rates with potential indeed occurs at the phase transition between the disordered and the c(2x2) ordered Br adlayer, resulting in a maximum diffusion rate near the onset of Br adlayer ordering.In addition, the diffusion of CH3Sad on c(2x2)-Brad covered Cu(100) was studied to test the hypothesis that the inverted potential dependence (the diffusion rates increase with increasing potential in the ordered coverage range) of Sad diffusion on this surface is attributed to a Br-induced exchange diffusion [5]. The methyl group should inhibit the exchange of sulfur with a Cu surface atom and thus suppress an exchange mechanism for steric reasons. We therefore expect that the diffusion of CH3Sad on c(2x2)-Brad covered Cu(100) shows the same potential dependence as the diffusion of Sad and CH3Sad on c(2x2)-Clad covered Cu(100) [6-7], that is, a decrease of the diffusion rate with increasing potential.We acknowledge financial support by the Deutsche Forschungsgemeinschaft via project no. 504552981.

NMR Spectroscopic Investigations of the Performance Limiting Mechanisms of Lithium-Sulfur Batteries

During the past decades, the development of alternative energy sources has become increasingly important as the growing consumption of non-regenerative fossil energy poses a threat to the environment. Hence, developing of next-generation batteries featuring high capacity, reduced costs and improved safety, such as in lithium-sulfur batteries, is of utmost importance. The benefits of lithium-sulfur batteries have led to widespread efforts to understand the fundamentals of the sulfur redox chemistry that drives their operation, as capacity fade has been observed in almost all Li-S batteries.[1] Therefore, the involved local structural changes that correlate with the (electro)chemical processes need to be unveiled during the operation of Li-S batteries, suitably by in situ and in operando methods. This presentation will demonstrate the development and application of one such (operando) technique: nuclear magnetic resonance (NMR) spectroscopy. NMR spectroscopic measurements allow the probing of the structural changes in a battery during electrochemical cycling. In particular, the application of a non-invasive experimental set-up, which can follow the reaction inside the battery in operando is highly desirable as it provides real-time structural information compared to ex situ analysis.[2] Lithium-sulfur batteries contain various NMR-active nuclear isotopes, like 7Li, 6Li and 33S, which allow the following of the chemical reactions during the charge-discharge process. This includes the transition between elemental sulfur and polysulfides on the cathode side, the formation of the solid-electrolyte interface (SEI) and the metal plating and stripping on the anode side. Herein, we use for the first time a combination of lithium and sulfur in operando NMR spectroscopy to reveal a fundamental understanding of the reaction pathway of lithium-sulfur batteries during the cycling process.Lithium NMR spectroscopy is a powerful technique to apply to batteries, as demonstrated by many previous investigations on different lithium battery systems, since it enables the detection of the chemical environments of lithium species during electrochemical cycling and parasitic reactions in the cell.[3] The great advantage of in operando 7Li NMR spectroscopy is that the 7Li signals of the lithium anode and the deposited metal differ due to the bulk magnetic susceptibility effects and the surface area, bringing the skin depth effect into play. Thus, this method enables a time-resolved and quantitative evaluation of the electrochemical metal deposition during electrochemical cycling. Therefore, it is possible to investigate a critical problem that reduces the cell performance – the formation of lithium dendrites. This lithium deposition is particularly problematic if it occurs uncontrolled and inhomogeneous and the exact mechanism of nucleation and propagation of dendrites is not yet fully understood.[4] The developed technique helps to understand this deposition to improve the safety during cycling. The interpretation of the electrolyte signal in the in operando 7Li spectra is much more difficult because of the overlapping signals. Therefore, in situ 33S and 6Li NMR spectroscopy supports the identification and quantification of (poly-)sulfides during the charge-discharge-process. 33S NMR experiments are rarely reported since 33S is a quadrupolar nucleus characterized by a low natural abundance and magnetogyric ratio, resulting in a very low receptivity. Nevertheless, the developed 33S NMR technique allows the detection of the formation Li2S under in operando conditions.[5] Additional in operando 6Li NMR experiments allow to follow the (poly-)sulfide formation as the spectra yield much sharper lines in asymmetric lithium environments in comparison to 7Li NMR experiments.[6] Thus, these techniques provide complementary results to the 7Li NMR spectroscopic studies and help to elucidate the sulfur redox mechanism in lithium-sulfur batteries.Our developed in situ NMR spectroscopic set-up is a powerful analytical method since real-time qualitative and quantitative detection of different sulfur and lithium species is crucial for understanding the electrochemical process in sulfur batteries. The first time, a combination of in operando lithium and sulfur NMR spectroscopy is presented, providing new insights at the molecular level that are essential for accelerating the development of lithium-sulfur battery technologies.[1] H. Wang, N. Sa, et al., The Journal of Physical Chemistry C 2017, 121, 6011–6017.[2] J. B. Richter, et al., Chemical Communications 2019, 55, 6042–6045.[3] R. Bhattacharyya, et al., Nat Mater 2010, 9, 504–510.[4] A. B. Gunnarsdóttir, et al., J Mater Chem A Mater 2020, 8, 14975–14992.[5] R. Musio, in Annu Rep NMR Spectrosc, 2006, pp. 1–88.[6] L. A. Huff, et al., Surf Sci 2015, 631, 295–300.

Comparison of electrochemical lithium and sodium metal deposition: A surface plasmon resonance spectroscopy investigation

Electrochemical deposition of alkali metals on the electrode surface is important for the development of metal-based batteries with high-energy density. Here, we investigate using electrochemical surface plasmon resonance spectroscopy (EC-SPR) to compare the deposition mechanisms of lithium and sodium metal. The SPR spectrum of the Cu film electrode was clearly observed for both LiPF6 and NaPF6 based organic electrolytes. The corresponding SPR spectra for both Li and Na system were dramatically red-shifted at 1st metal deposition process, indicated direct metal deposition on Cu surface. The Li system repeatedly showed similar red shift until at least the 2nd cycle, while similar red shift was not observed at all in the Na system. This indicated that direct Na-metal deposition on the Cu electrode surface was prevented by some passivation film, formed at 1st deposition process. The complex nature of Na-metal deposition, including the surface film phenomena, is responsible for the instability at the interface between the negative electrode and electrolyte in a Na-based battery system. This suggests that Na-based systems need to be more carefully designed and managed than Li-based systems.

Deposition of Sodium Metal at the Copper‐NaSICON Interface for Reservoir‐Free Solid‐State Sodium Batteries

Abstract“Anode‐free” solid‐state battery concepts are explored extensively as they promise a higher energy density with less material consumption and simple anode processing. Here, the homogeneous and uniform electrochemical deposition of alkali metal at the interface between current collector and solid electrolyte plays the central role to form a metal anode within the first cycle. While the cathodic deposition of lithium has been studied intensively, knowledge on sodium deposition is scarce. In this work, dense and uniform sodium layers of several microns thickness are deposited at the Cu|Na3.4Zr2Si2.4P0.6O12 interface with high reproducibility. At current densities of ≈1 mA∙cm−2, relatively uniform coverage is achieved underneath the current collector, as shown by electrochemical impedance spectroscopy and 3D confocal microscopy. In contrast, only slight variations of the coverage are observed at different stack pressures. Early stages of the sodium metal growth are analyzed by in situ transmission electron microscopy revealing oriented growth of sodium. The results demonstrate that reservoir‐free (“anode‐free”) sodium‐based batteries are feasible and may stimulate further research efforts in sodium‐based solid‐state batteries.

Electrochemical codeposition of La and Fe-group metals in a dicyanamide ionic liquid

Room-temperature electrochemical deposition of lanthanides and their alloys can be achieved employing organic ionic media, such as ionic liquids (ILs). Here, we study the electrochemical (co)deposition of La and Fe-group transition metals from solutions in 1-butyl-1-methyl-pyrrolidinium dicyanamide IL, [BMP][DCA], with controlled water content. We show that electroreduction of La(III) ions starts in the two-component solutions containing La(III) + Me(II) (Me = Co, Fe, or Ni) and no added water in the same potential interval as the electroreduction of respective Me(II). La is thus codeposited with the respective Fe-group metal, as evidenced by voltammetric, microscopic, and X-ray analyses, at considerably more positive potentials than in a solution containing only La(III) ions. Such a promoting effect is not observed in the presence of Cu(I) and Sn(II). Furthermore, the effect of water on the (co)deposition of La and Fe-group metals is systematically investigated. The La-Me (Me = Co, Fe, or Ni) codeposition is inhibited in the presence of moderate amounts of water (up to 0.32 M). At higher water contents, particularly ≥0.32 M H2O in the La(III) + Ni(II) solution, the electroreduction of La starts at more positive potentials than the deposition of Ni. This allows obtaining La-Ni deposits with a high La content. The XPS data indicate that La is present in the deposits in both metallic and oxidized states, even if deposition occurs in a solution with no added water. The results obtained in this study offer valuable insight into the electro(co)deposition of La from IL solutions and contribute to the progress of techniques for producing lanthanide-based functional coatings.

To Be or Not to Be – Is MgSc2Se4 a Mg‐Ion Solid Electrolyte?

AbstractMagnesium batteries offer promising potential as next‐generation sustainable energy‐storage solutions due to the high theoretical capacity of the magnesium metal anode. Facilitating dendrite‐free operation of metal anodes necessitates the development of solid electrolytes with high magnesium‐ion conductivity. While the chalcogenide spinel MgSc2Se4 is predicted to exhibit high magnesium ion mobility, unequivocal experimental evidence for magnesium ion conduction beyond short‐range motion is still missing. This study confirms magnesium‐ion transport in MgSc2Se4 through two independent electrochemical methods: electrochemical deposition of magnesium metal and reversible magnesium plating/stripping cycling. To overcome the difficulty of measuring the ionic conductivity of the mixed conducting MgSc2Se4 spinel, a pure ion conducting interlayer is employed in a symmetric transference cell. This approach effectively suppresses the electron transport, allowing accurate characterization of the ionic conductivity. The experimental results confirm a low migration barrier of (386 ± 24) meV for magnesium ion transport in MgSc2Se4 and demonstrate one of the best performances at room temperature among the reported inorganic magnesium solid electrolytes. The findings open a new door for exploring additional mixed magnesium ion conductors and highlight the potential of magnesium chalcogenide spinels as a promising class of magnesium solid electrolytes.

A Novel Approach to Study the Time-Varying Additive Activity during the Electrorefining of Copper

Electrodeposition additives are key components to enhance the electrochemical deposition of metals, either in pure plating applications or during the electrorefining of metals. Many different additives, either organic or inorganic, are applied in industry, depending on the type of process. This work focusses on thiourea and chloride as common additives used for copper electrorefining. This electrochemical industrial process consumes an impure copper anode and produces a pure (99.995 %) copper cathode, while the anode impurities remain in the electrolyte. Additives assist the electroreduction process to produce smooth copper deposits, essential to avoid short circuits and the formation of unwanted cathode morphologies which can entrap impurities.Thiourea is a crucial but complex additive in copper refining. It is known to degenerate into formamidine disulfide (FDS) and both thiourea as FDS can undergo interactions with either copper ions in the solution or the cathode surface. Time dependent additive studies and fundamental knowledge of the effect of aged electrolyte on the cathodic part of the electrorefining process are scarce.The approach applied in this work enables the investigation of the time dependent effect of additives, in this case thiourea and chlorides, assisting the electroplating of copper. Fundamental knowledge of the assisted plating process is extended to create a corner stone for applied research, subsequently, semi-industrial circumstances are used to describe the additive behaviour in industrial relevant conditions. Operando Odd Random Phase Electrochemical Impedance Spectroscopy (ORP-EIS) is used to study the electrochemistry of the additive system [1,2]. Hereby, a multisine input signal is added to the DC current to perform the ORP-EIS experiment simultaneously with the plating process. This measurement technique allows an in situ monitoring of the electrochemical system for hour-long electrodeposition processes. The ORP-EIS technique enables a quantification of the nonlinearities and non-stationarities during the EIS experiment [3]. Additionally, the present non-stationarities are modelled and the nonlinearities are considered as nuisance factor to result in a best linear time-varying approximation [4,5]. An equivalent electrical circuit is used as model to extract the relevant physical parameters from the impedance data. The EIS study is complemented with an ex situ analysis of the thiourea concentration, through ion chromatography, as a function of plating time. Correlations could be made between electrochemical parameters and actual thiourea concentrations [2].[1] T. Collet, et al., An operando ORP-EIS study of the copper reduction reaction supported by thiourea and chlorides as electrorefining additives, Electrochimica Acta (2021) 138762. [2] T. Collet, et al., The time-varying effect of thiourea on the copper electroplating process with industrial copper concentrations, Electrochimica Acta (2022) 141412. [3] Van Gheem, et al., Electrochemical impedance spectroscopy in the presence of non-linear distortions and non-stationary behaviour part i: Theory and validation, Electrochimica Acta 49 (2004) 4753–4762. [4] N. Hallemans, et al., Detection, Classification, and Quantification of Nonlinear Distortions in Time-Varying Frequency Response Function Measurements, IEEE Transactions on Instrumentation and Measurement, 70 (2021) 6500814. [5] N. Hallemans, et al., Best Linear Time-Varying Approximation of a General Class of Nonlinear Time-Varying Systems, IEEE Transactions on Instrumentation and Measurement, 70 (2021) 6503814.

(Invited) An Overview of Electrochemistry Application to Additive Manufacturing

Additive manufacturing (AM) is the process of creating three-dimensional (3D) objects from digital models through the sequential deposition of material in layers. This talk will highlight how researchers have used electrochemical research in additive manufacturing and will provide insights into how technology can be exploited to formulate novel microstructures and optimize the manufacturing process. Electrochemical 3D printing is a relatively new form of AM that creates metallic structures through the electrochemical reduction of metal ions from solutions onto conductive substrates. It involves localized electrochemical deposition of metals combined with additive manufacturing principles to achieve Electrochemical Additive Manufacturing (ECAM). The talk will also focus on the formulation of metal precursor inks to produce novel metallic microstructures and nanoalloys containing multiple metals. These inks are used with AM techniques to fabricate 2D and 3D printed conductive structures directly onto a substrate. Examples include aligned nickel nanowires over large areas, which provide opportunities to produce structures with enhanced anisotropic electrical and magnetic properties. Nanoalloy films printed using metal precursor inks have a variety of important applications involving local control of alloy composition in AM part. Examples include the facile formation of layered nanostructures and electrical conductivity with oxidative stability. The talk will conclude with current research on electropolishing of AM parts. AM while capable of producing complex-shaped metal parts with intricate internal geometries and lattice structures struggles to make parts with the smooth surface finish required for many applications. Polishing interior surfaces inaccessible to traditional surface polishing methods is a challenge. Electropolishing is increasingly being used as a post-treatment option for metal AM parts due to its non-contact nature and ability to finish complex internal features.

On the Road to Stable Electrochemical Metal Deposition in Multivalent Batteries

On the Road to Stable Electrochemical Metal Deposition in Multivalent Batteries

Vizuelizacija latentnih tragova papilarnih linija na bakarnim površinama taloženjem metala

When the papillary lines of the skin of fingers, palms and soles come into contact with the touched surface, a fingermark is created, which can be used to identify the person who left the evidence. The quality and usability of a fingermark as evidence for identification may depend on many factors. In order to justify the research, a statistical overview of the number of investigations performed at the crime scene with evidence found in general, as well as the number of fingermarks found, was presented. Given that the number of fingermarks found at the scene of crime in the territory of the police unit for the city of Belgrade is very large, and the percentage of identification of persons based on fingerprints is in the single digits, there is space for its increase. The success of personal identification could be improved by introducing new methods for visualizing fingermarks. The paper provides an overview of existing methods for visualizing latent fingermarks at the scene, as well as a comparison of individual methods for visualizing latent fingermarks on metal surfaces, such as copper. The method of metal deposition and the method of applying fingerprint (conventional) powders, based on carbon (instant black), on a metal surface such as copper, were used. A comparison of the visualized fingermarks was performed and their quality, i.e. potential for identification of persons was determined. The application of electrochemical metal deposition for the visualization of latent fingermarks gave satisfactory results with certain limitations, including the following: it is necessary to find a fingermark on an electrically conductive substrate; it is necessary to apply the method on the equipment located in the laboratory, on condition that the object with the latent fingermark is portable and of suitable dimensions and mass so that it can be immersed in the cell for electrolysis.

MODELING THE CONTENT OF COMPONENTS OF COMPOSITE ELECTROLYTIC COVER FROM THE POLARIZATION CURRENT

The composite coatings electrodeposition with the refractory metals and zirconium with cobalt makes it possible to obtain a coating with a unique combination of physicochemical properties that are unattainable when using other application methods. One of the reasons for the limited use of the electrolytic method of coating with such composites is the difficulty of controlling the process. The properties of alloys of the iron subgroup with refractory metals and composites depend not only on the chemical composition (the content of the refractory component) but also on the deposition conditions. Varying the polarization current density allows the creation of coatings of different compositions and, accordingly, different functional properties. The basis of the work was experimental research on the physicochemical patterns of electrolytic deposition of cobalt-based composite coatings by the galvanostatic current. The purpose of the work was to develop a mathematical model of the dependence of the cobalt-containing composite coatings formation on the polarization current density. The problem of describing the electrochemical deposition of metals, alloys and composite coatings is relevant since mathematical modeling is an integral part of the development of new and improvement of existing systems. A mathematical model is proposed to control the composition of composite electrolytic coatings based on cobalt, which allows obtaining coatings of a predetermined composition when varying the density of the operating current. It has been established that the composition of coatings, in particular the content of Co, Mo, W, can be controlled by varying the electrolysis current density, using quite simple developed mathematical models. The inclusion of Zr in the composition of composite coatings is described by a more complex model, in which the parameter values depend on both the concentration of the electrolyte components and the electrolysis conditions.

Quantitative estimate of the contribution of the surface diffusion process to mass transfer during electrochemical deposition of metals

In this study, an attempt was made to quantify the contribution of the surface diffusion process to mass transfer during electrochemical deposition of metals. The maximum density of nucleation centers is calculated, at which only diffuse overgrowth of a continuous layer of a new phase is possible. The time of diffusion overgrowth of a continuous monomolecular layer of a new phase is calculated. The results of independent experiments on the determination of boundery diffusion coefficients in a two-layer platinum-nickel thin-film system are analyzed. The value of the boundery diffusion coefficient of nickel at a temperature of 393K was found. The part of mass transfer due to surface diffusion of physically adsorbed atoms in relation to the total mass transfer during electrochemical deposition of metals has been quantified. It is proved that the role of the surface diffusion process in the formation of the coating during electrochemical deposition of metals is insignificant. It is shown that this is an indirect proof of the formation of an amorphous coating structure during electrochemical deposition of metal.

A new approach for producing of film structures based on Si1-xGex

In this work, we propose a new, previously unpresented in the literature, approach to the formation of Si1-xGex films. This approach includes electrochemical processes of the formation of porous silicon, electrochemical deposition of low-melting metals and Ge. Post-heat treatment is made possible to synthesize film structures based on Si1-xGex solid solutions. Using this approach an alloy of the composition Si0.4Ge0.6 has been obtained at a lower formation temperature than predicted by the phase diagram for the Si-Ge system.

Features of Fabrication of Titanium Dioxide Based Coatings for Non-Lithographic Template Electrochemical Synthesis of Micron Metal Particle Arrays

This work is devoted to the development of non-lithographic template methods of synthesis. These methods have a significant advantage in terms of structure formation: there is no need to design and produce masks, which greatly simplifies the process, and more of them can work with nonplanar substrates. The purpose of this study was to reveal the conditions for the synthesis of titanium dioxide xerogel films of different topologies as well as to develop a technique for non-lithographic template electrochemical synthesis of micron metal particles arrays and to study the structure of the resulting coatings. The films were deposited on the surface of substrates via dip coating. Specific topology of the films was achieved by template sol-gel synthesis. Their structures were analyzed by SEM and XRD. Template synthesis of metal micro particles were realized by pulsed electrochemical deposition of metals into the perforations of xerogel films. Obtained materials were analyzed by SEM and XRD; the element distribution on the surface was determined by the EDS detector of SEM. Based on the analysis results, we suggest the mechanisms of formation of the xerogel topology and proved the efficiency of pulsed electrodeposition for template synthesis of micron particles arrays.

(Electrodeposition Division Early Career Investigator Award Address) Regulating Electrochemical Deposition of Metals at Rechargeable Battery Electrodes

Scalable approaches for precisely manipulating the growth of crystals are of broad-based science and technological interest, and among the most extensively studied fields of research. New research interests have re-emerged in a subgroup of these phenomena—electrochemical deposition of metals in battery electrodes, such as zinc, an anode material that underpins several opportunities for developing cost-competitive technologies for large-scale electrical energy storage. Quantitative assessment shows that a high efficiency/reversibility of the electrochemical plating/stripping process (ie Coulombic efficiency > 99%), is necessary for the successful development practical rechargeable electrochemical energy storage systems that utilize a Zn metal anode. In practice, however, such efficiency values are usually below 80~90% in conventional metal plating/stripping systems.I will show that the inefficiency/irreversibility observed in metal plating/stripping is predominantly attributable to the metals’ susceptibility to parasitic chemical reactions and propensity for producing so-called “orphaned” fragments, which have lost electrical access to the electrode substrate termed the current collector. Both of these mechanisms are found to share the same origin— the non-uniform, rough electrodeposition morphology of metals. This finding motivates the overarching science question in this thesis: can the electrochemical growth of metals be strictly regulated in electrochemical cells? Despite the large volume of recent literature devoted to answering this question, the fundamental crystalline nature of the metal electrodeposits has been largely overlooked. Removing this artifice allows us to borrow knowledge from a rich body of literature on regulating the deposition process of crystalline materials to pursue fresh answers and approaches for achieving highly reversible electrodeposition of metals.Such approaches enable development of multiple strategies that are unprecedentedly effective in regulating metal deposition morphology and in achieving high-enough plating/stripping efficiency to meet the reversibility requirements as set forth. Specifically, I report that heteroepitaxy can be used to direct the shape and orientation of the metal crystallites formed on a rationally designed substrate. This strategy leverages crystals’ inclination for mimicking the atomic arrangement of the substrate surface, especially when the lattice misfit is below a critical value. Secondly, in I consider the fundamental limitation of heteroepitaxy—i.e. the correlation length is finite, meaning that the initial regulation of shape and crystallography of a metal deposit are only preserved for a finite electrodeposits thickness/electrode capacity. For as fundamental reasons, it is shown that this limitation can be overcome by imposing a convective flow normal to the electrode surface. The artificial convective flow serves as an additional solution-state mass transport mechanism and has a heretofore unexplored effect in suppressing chemotaxis-like reorientation of the metal crystallites at high areal capacities. I then demonstrate that solid-state metallurgy strategies for eliminating the built-in crystallographic heterogeneity of commercial foil-type metal electrodes, opens a fruitful path to powerful homoepitaxy regulation processes in which the metal itself is able to reversibly regulate its own electrodeposition morphology. In particular, subjecting a metal electrode to severe plastic deformation in the electrode foil-forming process is used to fabricate strongly-textured metal electrodes where such crystallographic heterogeneities are eliminated.In addition to these physical aspects, it is found that the chemical interaction at the heterointerface between the deposited metal crystallites and the substrate—which is actually a crystal of a different chemistry—also shows nontrivial influences on the electrodeposition process. I will assess consider these effects from two types of perspectives — oxygen- mediated bonding between the metal electrodeposit and substrate and alloying, respectively. The results suggest that the chemical affinity at the heterointerface is necessary to promote a uniform nucleation/growth landscape and to suppress the formation of “orphaned” metal deposits.

MODELLING APPROACH IN THE DEVELOPMENT OF ELECTROCHEMICAL 3D-PRINTING SYSTEMS

Background. New 3D-printing technologies are becoming more and more advanced and widespread in the twenty-first century. One of the types of 3D-printing is electrochemical 3D-printing, in which electrochemical deposition of metals is used to form metal products. Potentially, this method of 3D-printing is the most energy efficient, the least material-intensive, and also the easiest to implement. There- fore, research aimed at creating and improving systems for electrochemical 3D-printing is promising. Objective. The aim of the paper is to study the influence of geometric parameters of the system and the composition of the elec trolyte on the current distribution on the surface of the working electrode (cathode) in the process of electrochemical 3D-printing, and therefore print accuracy. Methods. Volt-amperometric measurements and multi-physical computer modelling of the secondary distribution of current density using COMSOL MULTYPHYSICS for different geometric parameters of the working part of the 3D-printer and different composition of electrolytes. Results. Based on the simulation of the secondary distribution of current density in copper sulphate electrolyte, it was found that the content of sulfuric acid in the solution should be minimal in order to purposefully deposit metal in the area directly under the working electrode. Based on the condition of maximum energy efficiency and accuracy of electrochemical 3D-printing, the optimal ratio between the deposition surface (cathode) and the edge of the non-conductive body of working electrode was found. Conclusions. It was established that in order to narrow the zone of current scattering (increase the accuracy of electrochemical 3D-printing) it is necessary to ensure the optimal ratio between the diameter of the capillary and the edge of the non-conductive body of the counter electrode. It was shown that this ratio should not be less than 5 [mm / mm]. Further applied research will be aimed at adaptation and practical implementation of the obtained model data, optimization of the electrolyte composition and design of the 3D-printer.

Multilayer Graphene—A Promising Electrode Material in Liquid Cell Electrochemistry

AbstractThe combination of imaging with electrochemical quantification in liquid cell transmission electron microscopy (TEM) provides opportunities for visualizing material processes in liquid with good spatial and temporal resolution in a way that is inaccessible in bench‐top electrochemical experiments. The electrode material used in liquid cell TEM determines the reliability and consistency of the electrochemical measurements and also influences the resolution when imaging processes on the electrode. Here, the opportunities arising from the use of 2D materials in liquid cell electrochemistry are explored. Through electrochemical imaging and modeling, it is demonstrated that the use of graphene electrodes enables quantitative study of electrochemical metal deposition and it is suggested that the minimal electron scattering and electric‐field enhanced wettability are advantageous in obtaining interpretable and higher resolution data. It is anticipated that incorporation of 2D materials into electrode design will present new opportunities for investigating problems in crystal growth, energy storage, and electrocatalysis.

Electrochemical Deposition of Cu Metal-Organic Framework Films for the Dual Analysis of Pathogens.

Metal-organic framework (MOF) thin films with flexible nature and prominent qualities have opened doors to new technological applications in different fields. Herein, we propose an electrochemical biosensor for the dual detection of Staphylococcus aureus based on the electrodeposition of Cu metal-organic framework (Cu-MOF) thin films. The promising sensing layer with features of good electronic conductivity and enhanced electron-transfer property can not only identify S. aureus through specific micrococcal nucleases in the supernatant but also detect the pathogen directly via aptamer recognition. The dual analysis design ensures the accuracy of this method for S. aureus detection in the range of 7-7 × 106 cfu/mL with the limits of detection of 1.9 and 5.2 cfu/mL. Moreover, the analytical method validation confirmed that the biosensor could efficiently work in complex biological samples, showing good selectivity and specificity and great potential for clinical diagnosis. More importantly, the current proposed strategy is simple and easy to implement without the need for extra signaling elements, which is convenient for timely clinical detection.