Electrocrystallization Process Research Articles

Electrodeposition fabrication of corrosion−resistant Ni–based composite film on surface of Cu: Role of conductive YSZ and non−conductive Si3N4 nanoparticles

The Cu materials are playing an irreplaceable role in modern marine facilities, while one major issue affecting their service life is corrosion attack caused by external erosion of chloride ions, which leads to the quickly structural deterioration and reduced durability. To solve this obstinate issue, the corrosion−resistant Ni−based composite films with conductive Yttria–stabilized zirconia (YSZ, 2.5–15 g/L) and non−conductive Si3N4 (2.5–15 g/L) reinforcing phases were composite–electrodeposited on Cu substrate in direct current (DC) mode. It was believed that the electrical differences of incorporated nanoparticles have a significant impact on nucleation and growth behaviors during electrodeposition, which further altered the structure and property of Ni−based composite films. Therefore, the emphasis of this study was to establish the correlation between obtained structure, electrochemical, and immersion corrosion performances at different incorporation levels of YSZ/Si3N4 nanoparticles. The results demonstrate that by increasing the total doping contents, the Electrochemical Impedance Spectroscopy (EIS) and Chronoamperometry (CA) measurements exhibited an initial increase followed by a subsequent decrease on co−deposition dynamics, which was related to the dominant impact of conductive YSZ nanoparticle at electrocrystallization process. Meanwhile, the moderate incorporation level of 15 g/L offered effective control over structural compactness through dispersion−strengthening and grain−refining, and the same ratio of YSZ/Si3N4 nanoparticles further maximized the improvement degree of microhardness, electrochemical passivation, and immersion stability of resulting films. Besides, the corrosion current density (jcorr) of Ni−YSZ−Si3N4 composite coating under optimum condition of 15 g/L was two orders of magnitude smaller than that of Cu substrate after long−term immersion test, and the corresponding polarization resistance (Rp) also increased by 8.6 times. Overall, these substantial alterations obtained provide effective guideline for the design and preparation of corrosion−resistant Ni−based composite coating, which is beneficial to prolonging the service life of Cu components in saline environments.

Turning crisis into opportunity: Intrinsically polarised low concentration eutectic electrolytes enable highly reversible zinc anodes

Low-concentration electrolytes (LCEs) hold great promise for sustainable energy storage due to their low viscosity, excellent wettability, and cost-effectiveness. However, their intrinsic polarization issues often lead to side reactions and dendrite growth, hindering their broader application. Herein, we present an approach to convert the negative effects of intrinsic polarization in LCEs into advantages, overcoming these challenges. The experimental and theoretical analyses demonstrate that acetate-adsorbed zinc anodes can harness the intrinsic polarization of LCEs to direct the electrocrystallization process on their surfaces. This promotes the preferential orientation of Zn(002) plane with high stability, resulting in symmetric batteries loaded with low-concentration eutectic electrolytes (LCEE) that maintain surprisingly low voltage polarization during the dendrite-free growth of up to 3150 h. In addition, by forming an organic-inorganic composite film enriched with N and Cl, LCEE achieves rapid migration of Zn2+. This allows Zn//PANI full batteries with LCEE to demonstrate superior capacity and cycling stability compared to other Zn-based batteries with LCEs. This study not only achieves a divergent design in LCEs but also provides clear guidance for future electrolyte development.

Magnetic field-assisted electrochemical additive manufacturing of nickel structure: Growth mechanism and microstructural evolution

The microstructure and crystal texture of magnetically assisted electrochemical additive manufacturing parts play crucial roles in their mechanical properties and applications. This paper elucidates the electrocrystallization process of electrochemical additive manufacturing by constructing a magnetically assisted setup and exploring both nucleation mechanisms and growth kinetics. The electrochemical behavior of the system was analyzed using electrochemical methods under different magnetic field strengths. Nickel structures with aspect ratios of 7.0 and 8.2 were fabricated using the experimental setup, and their morphology, crystal texture, and microstructure were characterized. The results showed that without applying a magnetic field, the nucleation mechanism followed three-dimensional instantaneous nucleation under diffusion control. Under magnetic field conditions, forced convection, double layer charging, and hydrogen evolution reactions were combined to modify the S-H nucleation model, demonstrating that the magnetic field can significantly enhance the nucleation rate and number of nuclei. The initial growth of the microstructure did not exhibit preferential solid orientation, primarily forming refined equiaxed grains. Subsequently, a characteristic pentagonal structure developed, followed by spiral dislocation growth, with a significant transformation of equiaxed grains into columnar crystals. The crystal orientation eventually evolved to <110>, with many twin boundaries, among which Σ3 grain boundaries accounted for more than 55 %. Applying a magnetic field improved processing efficiency, altered the morphology and texture of the material, refined the grains, and increased the types of twins. These results provide theoretical and experimental support for electrochemical additive manufacturing.

Regulating the inner Helmholtz plane with an electrophilic cation additive enabled stacked stratiform growth for highly reversible Zn anodes

Achieving consecutive flattening and dendrite-free deposition for the zinc anodes is essential to avoid internal short circuits or premature failure in the Zn-ion hybrid supercapacitor (ZHSC), which largely depends on the crystal growth during the electrocrystallization process. Herein, the tetrapropyl ammonium bromide additive was employed to reconstruct the inner Helmholtz plane (IHP) structure for manipulating the Zn deposition behavior and stabilizing the interfacial electrochemistry. Joint experimental and theoretical results show that electrophilic quaternary ammonium cations (TPA+) provoke the linkage effect after the specifical adsorption at IHP of the Zn electrode, which includes the molecular/ion distribution regulation, electrostatic shielding effect, crystallographic optimization, and solid electrolyte interphase (SEI) layer formation. The adsorbed TPA+ cations at IHP expel SO42− anions, bringing a reconfiguration of the ion/molecule distribution, which leads to a relatively uniform Zn2+ions distribution at electrode/electrolyte interface and a sluggish electroreduction reaction kinetics. Meanwhile, the electrostatic shielding effect regulates the crystallographic energetic preference of Zn deposits and induces the stratiform Zn growth and dominant Zn (002) texture. Concomitantly, the partial interfacial adsorbed TPA+ cations were electrochemically reduced to form the inorganic-organic hybrid SEI layer to further enhance the corrosion resistance and stability of the Zn electrode. Consequently, TPA+ cations mediated electrolyte enables Zn||Zn cells to exhibit a reversible plating/stripping performance for more than 2800 h. Additionally, a long-term cycling life can be obtained in the Zn||activated carbon ZHSC with this electrolyte. The electrolyte mediation strategy to realize the complementary interface effect and crystalline optimization provides promising feasibility on highly reversible Zn anodes.

Underpotential deposition of Cu onto Au(111) in the presence of acetate

The underpotential deposition (UPD) of Cu on Au(111) in the presence of acetate is investigated by cyclic voltammetry, potential step experiments, and in-situ STM imaging. The specific adsorption of acetate stabilizes the UPD monolayer (ML) of Cu on Au(111). Three distinct deposition processes are identified by cyclic voltammetry. The first two deposition processes corresponding to Cu sub-monolayer coverages are reversible. Strong kinetic effects arise for higher Cu coverage during the deposition and dissolution, which gradually lower the reversibility of the electrocrystallization process. Dissolution of the full Cu monolayer is shifted positively by about 0.3 V. In addition, bulk deposition is kinetically hindered for an extended potential region. The acetate coverage on the complete Cu monolayer is estimated to be 0.2–0.3 ML. It is proposed that adsorbed acetate on the Cu UPD ML is related to the kinetic hindrance observed in the experiments. (Surface) alloying of Cu and Au is observed by cyclic voltammetry and in-situ STM.

Directing (110) Oriented Lithium Deposition through High-flux Solid Electrolyte Interphase for Dendrite-free Lithium Metal Batteries.

Controlling lithium (Li) electrocrystallization with preferred orientation is a promising strategy to realize highly reversible Li metal batteries (LMBs) but lack of facile regulation methods. Herein, we report a high-flux solid electrolyte interphase (SEI) strategy to direct (110) preferred Li deposition even on (200)-orientated Li substrate. Bravais rule and Curie-Wulff principle are expanded in Li electrocrystallization process to decouple the relationship between SEI engineering and preferred crystal orientation. Multi-spectroscopic techniques combined with dynamics analysis reveal that the high-flux CF3 Si(CH3 )3 (F3 ) induced SEI (F3 -SEI) with high LiF and -Si(CH3 )3 contents can ingeniously accelerate Li+ transport dynamics and ensure the sufficient Li+ concentration below SEI to direct Li (110) orientation. The induced Li (110) can in turn further promote the surface migration of Li atoms to avoid tip aggregation, resulting in a planar, dendrite-free morphology of Li. As a result, our F3 -SEI enables ultra-long stability of Li||Li symmetrical cells for more than 336 days. Furthermore, F3 -SEI modified Li can significantly enhance the cycle life of Li||LiFePO4 and Li||NCM811 coin and pouch full cells in practical conditions. Our crystallographic strategy for Li dendrite suppression paves a path to achieve reliable LMBs and may provide guidance for the preferred orientation of other metal crystals.

Directing (110) Oriented Lithium Deposition through High‐flux Solid Electrolyte Interphase for Dendrite‐free Lithium Metal Batteries

AbstractControlling lithium (Li) electrocrystallization with preferred orientation is a promising strategy to realize highly reversible Li metal batteries (LMBs) but lack of facile regulation methods. Herein, we report a high‐flux solid electrolyte interphase (SEI) strategy to direct (110) preferred Li deposition even on (200)‐orientated Li substrate. Bravais rule and Curie‐Wulff principle are expanded in Li electrocrystallization process to decouple the relationship between SEI engineering and preferred crystal orientation. Multi‐spectroscopic techniques combined with dynamics analysis reveal that the high‐flux CF3Si(CH3)3 (F3) induced SEI (F3‐SEI) with high LiF and −Si(CH3)3 contents can ingeniously accelerate Li+ transport dynamics and ensure the sufficient Li+ concentration below SEI to direct Li (110) orientation. The induced Li (110) can in turn further promote the surface migration of Li atoms to avoid tip aggregation, resulting in a planar, dendrite‐free morphology of Li. As a result, our F3‐SEI enables ultra‐long stability of Li||Li symmetrical cells for more than 336 days. Furthermore, F3‐SEI modified Li can significantly enhance the cycle life of Li||LiFePO4 and Li||NCM811 coin and pouch full cells in practical conditions. Our crystallographic strategy for Li dendrite suppression paves a path to achieve reliable LMBs and may provide guidance for the preferred orientation of other metal crystals.

The Coordination of Titanium Ions and the Electrocrystallization Mechanism in Molten Chloride-Fluoride Salts

In electrochemical process, electrolyte composition is one of the key factors that determine the electrochemical behavior of elements. In this work, the nucleation mechanism and deposition process of titanium ions after the introduction of fluoride ions into molten salt were analyzed in detail by electrochemical technology, and the coordination behavior between fluorine ions and titanium was explored by molecular dynamics simulation, revealing the relationship between the electrocrystallization mechanism of titanium and its coordination properties. It can be found that the electrocrystallization mechanism of titanium ions is related to its coordination structure. Under our experimental conditions, the Ti-Cl bond in the system was gradually replaced by the Ti-F bond. This will lead to the change of charge transfer and ion diffusion of titanium ions, which will have an important effect on the electrocrystallization processes. This work has an important guiding significance for further study on the influence of different molten salt systems on the electrocrystallization mechanism of molten salt electrolytic titanium.

Morphology evolution of electrodeposited lithium on metal substrates

Lithium (Li) metal is deemed to be the high-energy-density anode material for next generation batteries, but its practical application is impeded by the uneven electrodeposition during charge of battery, which leads to the low Coulombic efficiency and potential safety issue. Here, multiscale modeling is fabricated to understand the morphology evolution of Li during electrodeposition process, from the self-diffusion of Li adatoms on electrode surface, to the nucleation process, and to the formation of Li microstructures, revealing the correlation between final morphology and deposition substrates. Energy batteries and self-diffusion of Li adatom on various substrates (lithium, copper, nickel, magnesium, and silver) result in the different nucleation size, which is calculated by kinetic Monte Carlo simulation based on classical nucleation theory. Formation of Li substructures that are grown from Li nuclei, is revealed by phase field modeling coupled with cellular automaton method. Our results show that larger Li nuclei is obtained under faster self-diffusion of Li adatom, leading to the low aspect ratio of Li substructures and the subsequent morphology evolution of electrodeposited Li. Furthermore, the electrodeposition of Li is strongly regulated by the selection of substrates, giving the practical guideline of anode design in rechargeable Li metal batteries. It is worthy to mention that this method to investigate the electro-crystallization process involving nucleation and growth can be transplanted to the other metallic anode, such as sodium, potassium, zinc, magnesium, calcium and the like.

Mechanism and kinetics of gold recovery and Au nanoparticle synthesis by Gas-Diffusion Electrocrystallization (GDEx)

Standing at the forefront of cutting-edge research, the electrochemical reduction of gases is not only driving the industrial shift towards electrification and decarbonization but also unlocking the immense potential to pioneer uncharted realms of electrochemical conversions, including metal transformations. Carbon monoxide issued from the electrochemical reduction of CO2 on gas-diffusion electrodes (GDEs), was used for the in-situ reduction of AuCl4− ions into elemental gold nanoparticles (NPs). A minimal extent of CO2 reduction on the uncatalyzed activated carbon of the GDEs was sufficient to fully remove the AuCl4− ions from the electrolyte bulk present in the aqueous electrolyte, while steering their complete precipitation as Au0. A maximum current efficiency of 19% towards CO formation was achieved, under a flow-through gas regime. The efficiency for Au0 precipitation was improved by manipulating the gas-flow regime and cathode polarization. The mechanism and kinetic description for gold recovery and nanoparticle synthesis are portrayed for the reactions underpinning the gas-diffusion electrocrystallization process (GDEx).

Compression promotes the formation of {110} textures during homoepitaxial deposition of lithium

Li metal is an advantageous anode material for high energy-density secondary batteries, while several technical issues, such as instabilities and dendrite formation, hinder its scalable deployment. The electrochemical deposition of Li is an electrocrystallization process where preferred crystallographic growth can be formed. The anisotropy of chemical and physical properties associated with the resulting preferred orientations (i.e., textures) can then be utilized to strengthen the Li metal anode. Understanding texture formation and evolution during homoepitaxial growth is essential for the typical setup of an excess anode inventory. Herein, based on pole figures, inverse pole figures and orientation distribution functions from X-ray diffraction, compression is found to be a critical factor for forming {110} textures during deposition on a Li substrate. Without compression and under a high Li+ transference number environment, a sharp {100}<110> texture is formed in the epitaxial layer up to the high deposition capacity of 20 mAh cm−2, inheriting and intensifying the pre-existing texture of the Li foil substrate. Compression alters the homoepitaxial texture by deformation and dynamic recrystallization to produce a peak-type {110} texture component close to {110}<111>. Due to the low diffusion barrier of Li adatoms and rapid redox process of Li/Li+, the {110} texture is confirmed to be a benefiting factor that enables reduced overpotentials, improved stability and suppressed moss-like dendrites in Li metal anodes. This study adds crystallographic factors to the electrochemo-mechanical correlations of Li metal anodes and provides new opportunities for further optimizations of cell assembly and operation.

Toward Precision Deposition of Conductive Charge-Transfer Complex Crystals Using Nanoelectrochemistry.

The lack of understanding for precise synthesis and assembly of nano-entities remains a major challenge for nanofabrication. Electrocrystallization of a charge-transfer complex (CTC), tetrathiafulvalene bromide (TTF)Br, is studied on micro/nanoelectrodes for precision deposition of functional materials. The study reveals new insights into the entire CTC electrocrystallization process from the initial nanocluster nucleation to the final elongated crystals with hollow ends grown from the working electrode to the neighboring receiving electrode. On microelectrodes, the number of nucleation sites is reduced to one by lowering the applied overpotential or precursor concentration. Certain current-time transients exhibit significant induction periods prior to stable nucleus growth. The induction regime contains small fluctuating current spikes consistent with stochastic formation of precritical nanoclusters with lifetimes of 0.1-30s and sizes of 20-160nm. Electrochemical analyses further reveal rate, size distribution, and formation/dissipation dynamics of the nanoclusters. Crystal growth of (TTF)Br is further studied on triangular nanoelectrode patterns with thickness of 5-500nm, which shows a mass-transfer-controlled process applicable for precision deposition of functional (TTF)Br crystals. This study, for the first time, establishes CTC nanoelectrochemistry as a platform technology for precise deposition of conductive crystal assemblies spanning the source and drain electrode for sensing applications.

Electrocrystallization Regulation Enabled Stacked Hexagonal Platelet Growth toward Highly Reversible Zinc Anodes.

Realizing durative flattened and dendrite-free zinc (Zn) metal configuration is the key to resolving premature battery failure caused by the internal short circuit, which is highly determined by the crystal growth in the electrocrystallization process. Herein, we report that regulating the molecular structure of the inner Helmholtz plane (HIP) can effectively convert the deposition into activation control by weakening the solvated ion adsorption at the interface. The moderated electrochemical reaction kinetics lower than the adatom self-diffusion rate steers conformal stratiform Zn growth and dominant Zn (0001) texture, achieving crystallographic optimization. Through in situ mediation of electrolyte engineering, orientational plating and stripping behaviors at edge-sites and tailored solvation structure immensely improve the utilization efficiency and total charge passed of Zn metal, even under extreme conditions, including high areal capacity (3 mAh cm-2 ) and wide temperature range (-40-60 °C).

Electrocrystallization Regulation Enabled Stacked Hexagonal Platelet Growth toward Highly Reversible Zinc Anodes

AbstractRealizing durative flattened and dendrite‐free zinc (Zn) metal configuration is the key to resolving premature battery failure caused by the internal short circuit, which is highly determined by the crystal growth in the electrocrystallization process. Herein, we report that regulating the molecular structure of the inner Helmholtz plane (HIP) can effectively convert the deposition into activation control by weakening the solvated ion adsorption at the interface. The moderated electrochemical reaction kinetics lower than the adatom self‐diffusion rate steers conformal stratiform Zn growth and dominant Zn (0001) texture, achieving crystallographic optimization. Through in situ mediation of electrolyte engineering, orientational plating and stripping behaviors at edge‐sites and tailored solvation structure immensely improve the utilization efficiency and total charge passed of Zn metal, even under extreme conditions, including high areal capacity (3 mAh cm−2) and wide temperature range (−40–60 °C).

ELECTRODEPOSITION AND PROPERTIES OF IRON DEPOSITS OBTAINED IN A MAGNETIC FIELD OF WEAK INDUCTION

The paper presented the electrodeposition, morphology and properties of iron deposits were obtained using a low-induction magnetic field of 0.001 T in the electrocrystallization process. The vector of magnetic field induction was directed perpendicular to the electrode surface. Iron deposits were obtained in an electrolyte FeSO4·7H2O – 1.5 mol/l and Al2(SO4)3·18H2O – 0.15 mol/l. The current density was 7 A/dm2. Deposits were obtained on a copper base. The influence of the magnetic field on the process of electrodeposition of deposits was studied using the method of stationary potentiometry and cyclic voltammetry. Determination of the influence of the magnetic field on the morphology of deposits was carried out using scanning electron microscopy. Determination of the properties of the obtained iron deposits was carried out by measuring microhardness, reflectivity and corrosion resistance. Studies have shown that a magnetic field with an inductance of 0.001 T affects the processes of electrodeposition of an iron deposit, increasing its overvoltage by more than 1 volt. The morphology of the deposits does not change significantly, but the crystallites obtained in the magnetic field have a more rounded shape and the surface of the deposit is more uniform. The microhardness of deposits obtained by electrodeposition without the use of a magnetic field was 2610 MPa, and with a magnetic field – 2720 MPa. The reflectivity of deposits obtained in a magnetic field is 17% higher. The corrosion resistance of deposits obtained in a magnetic field is approximately two times higher. After conducting corrosion studies, the microhardness of the deposits obtained using a magnetic field did not change (2630 MPa), however, the microhardness of the deposits obtained under normal conditions decreased by approximately two times. Electrolysis parameters for maximum corrosion resistance, microhardness and reflectivity are proposed in the work.

A Study on the Anodic Electrodeposition of Iridium Oxide on Different Substrates

The anodic electrodeposition process of iridium oxide on Ti, Pt, Au, and glassy carbon was investigated from cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). The electrocrystallization process of iridium oxide electrodeposition based on different substrates behaved consistent with the diffusion-controlled three-dimensional nucleation process, and a nucleation mode capable of expressing the process was established. Depending on the nucleation model parameters, the iridium oxide electrodeposition on Ti with the highest nucleation rate and active nucleation sites showed excellent nucleation performance, while the value of the electrodeposition on Au is the largest, indicating that Au-base electrodeposited iridium oxide can support more favorable kinetics for OER. Furthermore, the morphology and chemical composition of the electrodeposited IrOx electrodes based on different substrates were characterized by scanning electron microscope (SEM) and X-ray photoelectron microscopy (XPS), and then measured through a series of electrochemical characterization experiments. Although the SEM image of IrOx layer electrodeposited on Ti is relatively uniform and have higher IrO2 content compared to other substrates, its electrocatalytic activity is poor, while the IrOx-Au electrode exhibits the best OER performance with a current density of 10 mA cm−2 and an overpotential of 0.2 V.

Investigation of the Mechanism of Cocrystal Formation at the Polarized Liquid-Liquid Interface

The cocrystals of two reagents of mismatch solubility, hydrophilic caffeine and lipophilic 1-hydroxy-2-naphthoic acid, were obtained at a water-oil interface. 1 By analysing the product collected at the phase interface by X-ray diffraction and Raman spectroscopy, we confirmed that we obtained the molecular cocrystals of caffeine and 1-hydroxy-2-naphthoic acid, free of starting reagents and solvents. Polarisation of the interface allowed the electrochemical control of the cocrystallisation process: for non-polarised interfaces, a mixture of phase I and II cocrystals were obtained, whereas cocrystals of phase I were formed when a high interfacial potential was applied. The difference between the polymorphs obtained in the absence or in the presence of interfacial polarisation is attributed to the different cocrystallisation mechanisms. In the absence of interfacial polarisation, caffeine and 1-hydroxy-2-naphthoic acid are cocrystallising through an interfacial process. When the interface is positively polarised, cationic form of caffeine is transferred to the organic phase, the complex with naphthoic acid is formed and the proton is released. The pH increased after cocrystallisation, suggesting that the liberated H+ remained in the organic phase. On the contrary, in the absence of polarisation or in the case of low interfacial potential the protons are remaining in the aqueous phase what resulted in a decrease in pH after cocrystallisation process. We demonstrated an indirect evidence of the transfer of caffeine upon chemical polarization of the interface. We observed almost no deposits in the organic phase by analysing it with a scanning electron microscope.We investigated here the mechanism behind the formation of cocrystals by using the polarized interface between two immiscible electrolyte solutions (ITIES).2 For the purpose of this study, the two solutions have been placed in contact3 : one being an aqueous solution of caffeine, as a model drug substance, and the second being organic solution of 1-hydroxy-2-naphthoic acid (cocrystal component) and the salt inducing the suitable imposed potential difference. The formation of the caffeine: 1-hydroxy-2-naphthoic acid complex was studied by changing the salts present in the aqueous phase, the chemical compounds imposing potential in organic phase, varying the organic solvents and the temperature at the liquid-liquid interface. The cocrystals collected at the interface were analysed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and low frequency Raman spectroscopy. We studied the proportions of polymorphic phases as a function of changing conditions. To understand the mechanism behind the caffeine transfer and the formation of different forms of polymorphic crystals at the water-oil interface, Electrochemical Noise Experiments4 have been carried out. A four-electrode system was used to apply zero volts between the working electrode and the counter electrode and then measuring the current and the potential versus the reference electrode. Such a setup allows the measurement of potential and current as the function of time simultaneously. We could thus follow the phenomena that are taking place at the interface. The measurements were carried out by varying the cations (tetraalkylammoniums, Li+, K+) in aqueous and organic phase as well as the anions (derivatives of tetrakis(phenyl-borate) in organic phase). The experimental results were supported by theoretical equations and applied to the system containing caffeine.This novel strategy of cocrystallization, was followed by the investigation of other coformers (3-hydroxy-2-naphthoic acid) and drugs (cocrystals of ketoprofen with amino acids and carboxylic acids) in order to validate the method. Such an electrocrystallization process at the ITIES will open new opportunities for the formation of drugs cocrystals. M. Kaliszczak et al., CrystEngComm (2022) doi: 10.1039/D1CE01281A.Z. Samec, Pure Appl. Chem., 76, 2147–2180 (2004).S. J. Diez et al., Cryst. Growth Des., 18, 3263–3268 (2018).I. B. Obot, I. B. Onyeachu, A. Zeino, and S. A. Umoren, J. Adhes. Sci. Technol., 33, 1453–1496 (2019).

Epitaxial Electrocrystallization of Magnesium via Synergy of Magnesiophilic Interface, Lattice Matching, and Electrostatic Confinement.

Rechargeable magnesium batteries are particularly advantageous for renewable energy storage systems. However, the inhomogeneous Mg electrodeposits greatly shorten their cycle life under practical conditions. Herein, the epitaxial electrocrystallization of Mg on a three-dimensional magnesiophilic host is implemented via the synergy of a magnesiophilic interface, lattice matching, and electrostatic confinement effects. The vertically aligned nickel hydroxide nanosheet arrays grown on carbon cloth (abbreviated as "Ni(OH)2@CC") have been delicately designed, which satisfy the essential prerequisite of a low lattice geometrical misfit with Mg (about 2.8%) to realize epitaxial electrocrystallization. Simultaneously, the ionic crystal nature of Ni(OH)2 displays a periodic and hillock-like electrostatic potential field over its exposed facets, which can precisely capture and confine the reduced Mg0 species onto the local electron-enriched sites at the atomic level. The Ni(OH)2@CC substrate undergoes sequential Mg-ion intercalation, underpotential deposition, and electrocrystallization processes, during which the uniform, lamellar Mg electrodeposits with a locked crystallographic orientation are formed. Under practical conditions (10 mA cm-2 and 10 mAh cm-2), the Ni(OH)2@CC substrate exhibits stable Mg stripping/plating cycle performances over 600 h, 2 orders of magnitude longer than those of the pristine copper foil and carbon cloth substrates.

Mixed mode oscillations in an electrochemical reactor

This paper subject focuses on modelling of electrochemical processes during a deposition of nanostructured materials on a metallic substrate. Fundamentals of electrocrystallization processes and parameters influenced the final quality of the resulting products are considered. To quantify the evolution of the electrochemical reactor processes with respect to time, an equivalent electric circuit has been established. Two types of periodic supplying currents were taken into consideration: bipolar pulse current and sinusoidal rectified current. Results of performed computer simulations of electrocrystallization processes with the focus on mixed mode oscillations (MMOs) as the dynamical switches between small amplitude oscillations (SAOs) and large amplitude oscillations (LAOs) are presented. The established circuit model can lead to methods for fast treating large quantities of electrocrystallizator data and extracting from them kinetic parameters importantly influenced the structure of the produced materials.

Electrochemical reduction of V2O5 in the (NaCl–KCl–NaF) molten salt

The preparation of high purity metal vanadium is a challenging work, it is an important way to prepare vanadium tools by molten salt electrodeposition. Therefore, it is of great significance to study the electrochemical reduction mechanism and crystallization process of vanadium oxide in a specific molten salt. The electrochemical reduction mechanism of V2O5 in the molten salt of NaCl–KCl–NaF and its electrocrystallization process were investigated by voltammetry, chronopotentiometry, and chronoamperometry. The results indicate that the electrochemical reduction process of V2O5 is a reversible reaction with five electrons in one step and the generation of insoluble products, controlled by diffusion, with a reaction equation of VO3− + 5e− = V + 3O2−. The electrocrystallization process of V is an instantaneous hemispheroid three-dimensional nucleation process. When the temperature of the molten salt is 983 K, the mole fraction of each component in the salt is XNaCl = 0.35, XKCl = 0.35, and XNaF = 0.3. When the mass fraction of V2O5 is 5%, the active V ion exists in the form of VO3−, and its diffusion coefficient is 1.033 × 10−7 cm2 s−1.