Galvanostatic Deposition Research Articles

Electrochemical Behaviour of Nickel(II)-Rhenium(VII) And Electrodeposition of Nickel-Rhenium Alloy from Choline Chloride - Urea Deep Eutectic Solvent

The electrochemical behaviour of nickel(II)-rhenium(VII) and the electrodeposition of nickel-rhenium alloy using choline chloride: 2 Urea deep eutectic solvent (Reline DES) is reported. Speciation of nickel(II)-rhenium(VII) in Reline DES was studied using UV -Visible spectroscopy. Cyclic voltammetry of Ni2+-ReO4 − in Reline indicates the simultaneous reduction of two metal ions at glassy carbon electrode controlled by non-reversible diffusion process. Chronoamperograms obtained for the reduction of Ni2+-ReO4 − suggests nucleation and three-dimensional growth of bimetallic phase on electrode surface followed progressive nucleation. Electrodeposition of nickel—rhenium alloy was carried out on copper substrates under galvanostatic and potentiostatic conditions. Smooth and uniform deposits were obtained by galvanostatic deposition. X-ray diffraction analysis of the deposit confirmed it to be nickel-rhenium alloy (at −1.2 V) in amorphous form which upon annealing at 1000 °C crystallizes into hexagonal phase with concurrent morphology change from spherical particles to irregular polygons.

Investigation of the Gas Permeation Stream through Gas Diffusion Electrodes for CO2 Electrolysis and Possible Links to Selectivity

The electrochemical reduction of CO2 (eCO2R) is one promising attempt to create value added products from excess greenhouse gas with renewable energy. However, to become commercially relevant, some challenges have to be outgrown. To overcome the challenge of mass transport limitations on planar electrodes, Gas-Diffusion-Electrodes (GDE) have been implemented for eCO2R, allowing to reach sufficient reaction rates with the CO2 directly being delivered to the catalyst layer [1]. A major issue in the application of GDEs for eCO2R represents flooding of the mostly carbon based gas diffusion media by the alkaline electrolyte during application. This phenomenon results in a detrimental change of the 3-phase boundary and is accompanied by a loss of activity and a breakdown of performance [2]. A possible approach to avoid flooding of the GDE during eCO2R is to apply a backpressure in order to increase the capillary pressure inside the GDE, which needs to be balanced accurately, since excess backpressure can cause a CO2 crossover stream through the GDE into the electrolyte compartment [3]. In our work we investigate the permeation behavior of GDEs in a customized flow cell and investigate how to influence it via electrode preparation. A deeper understanding of the permeation characteristics of GDEs could lead to a better choice of operation points regarding flooding issues. However, the operation point itself and the preparation of GDEs could impact not only the flooding behavior of the electrode but also selectivity of the reaction. The eCO2R is taking place ~10 µm away from the gas-liquid boundary. The distribution of the two phases inside the GDE is crucial for the reaction pathway [4]. Therefore, we examine possible links of permeation behavior and electrode preparation on selectivity.In detail, our setup contains a customized flow cell in which the pressure in the gas compartment is adjusted with a needle valve and monitored via a pressure transmitter. The gas-crossover stream through the GDE is then registered by collecting the gas transferred to the liquid electrolyte in a measuring cylinder.For electrode preparation, commercial carbon based GDLs (25BC-Sigracet, H23C8-Freudenberg) are pretreated by either spray coating a carbon-ionomer-layer on top of the microporous layer or sputter coating with copper first. In the second step, a galvanostatic deposition of copper is carried out on the pretreated GDLs.The permeation behavior is tested for the non-coated commercial GDLs, the GDLs after the pretreatment step and after deposition of copper without and with current applied, respectively. In our experiments the crossover stream related to backpressure through the GDL H23C8 was lower compared to the crossover stream through GDL 25BC, most likely being linked to differences in the porosity and cracks of the MPL (Figure 1A). However, when comparing identically prepared GDEs based on different GDL types at the same crossover stream, only minor changes in selectivity can be observed (Figure 1B). It was also found that the crossover stream was influenced by the coating of the electrode. While sputter coating (spu) has a minor impact on gas permeation, spray coating (spr) leads to a significant change. These observations could be related to increased electrode wetting after spray- but not after sputter coating. The permeation behavior after galvanic deposition of copper is comparable, independent of the pretreatment procedure. Comparing the selectivity of GDEs with the different pretreatment procedure, a significant change in selectivity can be observed (Figure 1C). In the next steps, it will be crucial to investigate if this selectivity change is related to a different gas-liquid distribution in the GDE or to other factors as the composition of the coating layer to successfully influence operation stability and selectivity.

Convenient and Accurate Detection of Dopamine and Glucose by Modifying Carbon Fiber Electrodes

Fast, sensitive, and low-cost high-performance detectors have gradually become an indispensable tool for people to keep healthy, and sensors are the key devices of detection equipment. In this work, a ZnO nanocrystal modified carbon fiber electrode was prepared using a hydrothermal method, and on this basis, a galvanostatic point deposition method was used to load copper nanoparticles to prepare a sensor electrode. Scanning electron microscopy and X-ray diffraction were used to comprehensively analyze composition, morphology, and environmental adaptability of the prepared electrodes. The DPV test was used to verify the enhanced effect of ZnO nanorods on neurotransmitter detection. The ZnO/CF showed an obvious electrical signal (0.22 V, 4 × 10−5A) in the detection of dopamine (DA) solution, and the Cu-NPs/ZnO/CF also showed excellent detection results in the glucose detection experiment., providing two excellent examples for the development of low-cost electrochemical sensors. The electrodes can specifically detect DA in the presence of ascorbic acid and uric acid, and the detection limit of the electrode for detecting DA is about 0.4 μM. In addition, the Cu-NPs/ZnO/CF electrode successfully realized the enzyme-free detection of glucose, and the detection limit could reach 0.5 μM.

Crystallographic and electrochemical corrosion resistance analyses of cataphoretically co-deposited spinel Co>0.5Mn0.1-0.3O0.1-0.4@rGO composites over α-Fe(110) as current collector for supercapatteries

Binder free spinel Co>0.5Mn0.1-0.3O0.1-0.4@rGO composite electrode films were fabricated via galvanostatic electrochemical deposition technique over α-Fe(110) as current collector for hybrid supercapattery. Self-designed, n-MOSFET embedded ATMega328P microcontroller assisted modules were deployed to record the chronopotentiometric as well as galvanostatic charging-discharging analysis for specific capacitance (Cs) measurements. Partial, exchange as well as limiting current densities(iL) and cathodic current efficiency were estimated. Electrochemical signature was analyzed from cyclic voltammetry data. Morphology and chemical nature of the composites were scrutinized with scanning electron microscopy, X-ray photoelectron, FT-IR and Raman spectra. Indigenously designed computer simulation programs coded in Python were used to optimize the deposition parameters and to analyze the crystalline structure from XRD data. The unit cell length for the FCC crystal with an octahedral geometry was ∼ 4.28 Å. An in-depth analysis of potentiodynamic polarization as well as electrochemical impedance spectral data were carried out to scrutinize the corrosion resistance and capacitance characteristics of the composites in KOH. From the Tafel constants, Ecorr, Icorr, Ru, RCT and ZW data, it was accentuated that rGO incorporated composite films offer enhanced corrosion protection for Fe(110) substrates than their individual counterparts along with augmented specific capacitance. Estimated Cs was about 1166 F.g−1 at a scan-rate of 10 mV.s−1. Impact of time-constant (τ) and current density over Cs was analyzed via GCD technique and was about 1458.73 F.g−1 at 2 τ and at 0.5 A.g−1. And the corresponding specific energy and power density were about 183.23 W.h.kg−1 and 237.75 W.kg−1 respectively. These composite electrode films impregnated with rGO not only improved the specific capacitance but also imparts the sacrificial corrosion resistance over the α-Fe(110) as current collector in presence of OH−as electrolyte and can serve as a sustainable electrode material for supercapatteries.

Array-wide uniform PEDOT:PSS electroplating from potentiostatic deposition

Electroplating of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) is important in many neuroelectronic applications but is challenging to achieve uniformity on large-scale microelectrode arrays (MEA) using conventional galvanostatic methods. In this study, we address this challenge through a potentiostatic method and demonstrate highly uniform electroplating of PEDOT:PSS on MEA with more than one hundred electrodes, all at cellular sizes. The validation of this approach involves comparisons with galvanostatic deposition methods, showcasing unparalleled deposition yield and uniformity. Systematic electrochemical characterizations reveal similarities in structure and stability from potentiostatic deposited coatings. The advances developed here establish the potentiostatic method and detailed process to achieve a uniform coating of PEDOT:PSS on large-scale MEA, with broad utility in neuroelectronics.

Electrodeposition of Phase–Pure n–Type Cu2O: Role of Electrode Reactions and Local pH

Cuprous oxide (Cu2O) thin films, antithetically exhibiting n-type conductivity, were electro–deposited on Fluorine-doped Tin Oxide (FTO) coated glass substrates. Linear sweep voltammetry, chronoamperometry, and chronopotentiometry studies coupled with structural characterization of the deposit identify the occurrence of multiple reduction reactions, including “corrosion” of Cu2O to Cu. Interestingly, an underpotential conversion (negative of +0.039 V vs Ag/AgCl) of the Cu2O film to Cu islands is observed during potentiostatic deposition. The same process is also shown as a potential spike in chronopotentiometry curves, during galvanostatic deposition, at current densities that are cathodic of −0.2 mAcm−1. The reason for the formation of Cu is attributed to the decrease in local pH in the vicinity of the working electrode, whence thermodynamic conditions favor the formation of Cu. The proroguation of Cu formation is achieved by continuously stirring the solution, thereby stabilizing the pH at the electrode. Deferment of film corrosion to increasingly longer times is observed with increasing stirring rates. Mott-Schottky analysis of phase-pure films reveals the formation of degenerately doped n-type Cu2O films (n ∼1020 cm−3). The phase pure Cu2O films could be used as an electron transport layer in several photo-conversion devices and ultimately pave the way for an oxide homojunction device.

Facile In-Situ Electrosynthesis of MnO2/RGO Nanocomposite for Enhancing the Electrochemical Performance of Symmetric Supercapacitors

One-pot galvanostatic reverse pulse electrochemical deposition (RPED) was used to create a supercapacitive electrode made of manganese dioxide/reduced graphene oxide (MnO2/RGO) nanocomposite. Systematic changes of two independent parameters of the reverse pulse current, including times of the anodic and cathodic pulses (ta and tc), were investigated to achieve the desired physicochemical and electrochemical properties. Galvanostatic charge–discharge, cyclic voltammetry, and electrochemical impedance spectroscopy tests were employed to perform electrochemical evaluations. According to the results, the MG50-5 nanocomposite, synthesized at ta = 50 ms, tc = 5 ms, and anodic peak current density of 2 mA cm−2, was selected as the optimal sample. This sample showed the highest specific surface area of 284.6 m2 g−1 and the specific capacitance of 789.0 F g−1 at a current density of 0.5 A g−1. The specific capacitances of the MG50-5 symmetric supercapacitor at current densities of 0.5 and 10 A g−1 were 660.14 and 402.50 F g−1, respectively. Maintaining 84.8 % of the specific capacitance after 5000 consecutive cycles at 4 A g−1 indicated stable cycle performance of the MG50-5 symmetric cell. The MG50-5 symmetric supercapacitor presented the maximum energy density of 22.92 Wh kg−1 at a power density of 156.3 W kg−1 and the maximum power density of 3.125 kW kg−1 at an energy density of 13.97 Wh kg−1. Therefore, optimizing reverse pulse current parameters in the galvanostatic RPED of MnO2/RGO nanocomposite leads to an outstanding electrochemical performance of the fabricated supercapacitors.

Influence of deposition conditions on performance of Ni3S2 as the bifunctional electrocatalyst in alkaline solutions by galvanostatic deposition

The electrodeposition method is a popular synthesis method due to its low cost, simplicity, and short synthesis time.

Electrochemical Signatures of Potassium Plating and Stripping

Alkali metals are attractive anodes for high energy density batteries, but practical utilization of these materials in rechargeable cells has so far been hindered by safety concerns, limited Coulombic efficiencies and short cycle lives. These issues are all connected to the uneven electrodeposition and stripping of alkali metals; dendritic metal deposits can short circuit the cell and deposits with large surface areas consume more electrolyte and active material in side reactions.[1] To circumvent these problems, one of the approaches which have been attempted is electrolyte engineering. For instance, electrolytes with higher salt concentration, so called highly concentrated electrolytes, have been shown to suppress both dendrite growth and increase the Coulombic efficiency of metal anodes.[2,3] When different metal anode stabilization strategies are evaluated, it is common to perform galvanostatic cycling experiments in symmetric or asymmetric cells. This allows the cycling stability and Coulombic efficiency of the plating/stripping to be analyzed. Additionally, it is common to use features of the voltage profile as signatures on the mechanisms responsible for changes in electrochemical performance. For instance, a sharp decrease in (over)voltage during plating/stripping is a sign of a short circuit. A gradually increasing overvoltage during cycling on the other hand can be a result of continuous solid electrolyte interphase (SEI) buildup. However, several processes often occur in parallel when symmetric/asymmetric cells are cycled galvanostatically, each giving different contributions to the voltage profile which need to be deconvoluted to make sense of the data. In this contribution, we use three-electrode cells in combination with simple electrochemical experiments like cyclic voltammetry, chronoamperometry and chronopotentiometry to disentangle the contributions to different features in the galvanostatic voltage profiles of alkali metal anodes.In particular, we dissect the voltage profiles of potassium-copper (K-Cu) cells with highly concentrated electrolytes. Due to the higher reactivity of K compared to other alkali metals, certain features in the voltage profiles of these cells become exaggerated compared to lithium or sodium metal cells. We show that during galvanostatic deposition on a fresh Cu substrate, SEI formation and nucleation occur partly in parallel. If an SEI-formation step is performed prior to the galvanostatic deposition, a much sharper ‘nucleation peak’ in the voltage profile can be observed, indicative of the higher rate of nucleation that needs to occur in this case. Further, the potassium metal anode exhibits a steplike voltage profile from the second cycle and onwards. We confirm that this feature arises because bulk K is covered by a resistive native layer, whereas another type of, less resistive, interphase covers the freshly deposited K. This inhomogeneous interphase will inevitably promote preferential and inhomogeneous plating/stripping.

Substrates with Different Magnetic Properties Versus Iron-Nickel Film Electrodeposition

Abstract The hereby work presents the iron-nickel alloys electroplated on the different metallic substrates (aluminium, silver, brass) using galvanostatic deposition, with and without presence of the external magnetic field (EMF). The films were obtained in the same electrochemical bath composition - mixture of iron and nickel sulphates (without presence of additives) in the molar ratio of 2 : 1 (Ni : Fe), the electric current density (50.0 mA/cm2), and the time (3600 s). The mutual alignment of the electric (E) and magnetic field (B) was changeable - parallel and perpendicular. The source of EMF was a set of two permanent magnets (magnetic field strength ranged from 80 mT to 400 mT). It was analysed the surface microstructure, composition, morphology, thickness and the mechanical properties (roughness, work of adhesion). The surface morphology and the thickness of films were observed by Scanning Electron Microscopy (SEM) and Confocal Laser Scanning Microscopy (CLSM). The elemental composition of all FeNi films was measured using Wavelength Dispersive X-Ray Fluorescence (WDXRF). The crystalographic analysis of the deposits was carried out by X-Ray Diffraction. Depending on the used substrate, modified external magnetic field orientation influenced the tribological and physio-chemical properties of the deposited layers. The diamagnetic substrates and EMF application reduced the FeNi thickness and the average crystallites size, in contrast to the paramagnetic substrate. Parallel EMF increased the value of the tribological parameters for CuZn and Ag but decreased for Al. The content of FeNi structure was rising in the case of diamagnetic substrate and the dependence was opposite on the paramagnetic substrate.

(Invited) Electrodeposition of Manganese Arsenides (MnxAs) as Promising Candidates in Spintronics

Spintronics is a new branch of electronics in which the spin of the electrons as well as their charge is manipulated to produce a desired outcome. Spintronic devices are particularly attractive for memory storage and magnetic sensor applications, and potentially for quantum computing where the electron spin would represent a bit of information. Nowadays many efforts are made to increase the efficiency and lower the production costs of these materials, among others the use of molecular inorganic compounds and cheap preparation techniques [1].Most of these layers are synthesized with physical and/or vapor phase techniques [2] which allow to obtain materials with a very few defects, but which are complex to manage and typically very expensive. For this reason, in this study we have searched for a way to electrochemically deposit a compound with interesting spintronic properties in the aqueous medium. In fact, electrodeposition is notoriously a very cheap, versatile and easily scalable technique.With this purpose Mn-As system was selected thanks to its good magnetic and transport properties to be used as building blocks for spin valve [3]. MnAs has potential applications in spintronics, for electrical spin injection into GaAs and Si based devices [4] and DFT simulations predict that Mn2As and Mn3As have a low magnetization saturation and a high spin polarization at the Fermi-level [5]. Starting from MnSO4 and NaAsO2 precursors solutions with various concentrations, supporting electrolytes and pH were tested.The electrochemical behaviour of the precursors was investigated with cyclic voltammetries and both potentiostatic as well as galvanostatic deposition were carried out. The deposits obtained were morphologically and compositional characterised with scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS) and X-ray fluorescence spectroscopy (XRF), the chemical states were analysed with X-ray photoelectron spectroscopy (XPS), the crystalline structure was investigated with X-ray diffraction measurements (XRD). The preliminary magnetic and transport measurements evidence the promising properties of this deposition process to provide spinfiltering materials.The authors acknowledge Regione Toscana POR CreO FESR 2014-2020 – azione 1.1.5 sub-azione A1 – Bando 1 “Progetti Strategici di ricerca e sviluppo” which made possible the project “RAM-PVD” (CUP 3647.04032020.157000057_1225).

In Vitro Evaluation of Ag- and Sr-Doped Hydroxyapatite Coatings for Medical Applications.

Osseointegration plays the most important role in the success of an implant. One of the applications of hydroxyapatite (HAp) is as a coating for metallic implants due to its bioactive nature, which improves osteoconduction. The purpose of this research was to assess the in vitro behavior of HAp undoped and doped with Ag and/or Sr obtained by galvanostatic pulsed electrochemical deposition. The coatings were investigated in terms of chemical bonds, contact angle and surface free energy, electrochemical behavior, in vitro biomineralization in acellular media (SBF and PBS), and biocompatibility with preosteoblasts cells (MC3T3-E1 cell line). The obtained results highlighted the beneficial impact of Ag and/or Sr on the HAp. The FTIR spectra confirmed the presence of hydroxyapatite within all coatings, while in terms of wettability, the contact angle and surface free energy investigations showed that all surfaces were hydrophilic. The in vitro behavior of MC3T3-E1 indicated that the presence of Sr in the HAp coatings as a unique doping agent or in combination with Ag elicited improved cytocompatibility in terms of cell proliferation and osteogenic differentiation. Therefore, the composite HAp-based coatings showed promising potential for bone regeneration applications.

The Electrodeposition of Derivatives of Pyrrole and Thiophene on Brass Alloy in the Presence of Dodecane-1-Sulfonic Acid Sodium Salt in Acidic Medium and Its Anti-Corrosive Properties

In this paper, potentiostatic and galvanostatic deposition (electrochemical deposition) processes have been used for the obtained of a new composite polymer: N-methylpyrrole-sodium 1-dodecanesulfonate/poly 2-methylthiophene (PNMPY-1SSD/P2MT) coatings over brass electrode for corrosion protection. The sodium 1-dodecanesulfonate as a dopant ion employed in the electropolymerization procedure can have a meaningful effect on the anti-corrosion protection of the composite polymeric film by stopping the penetration of corrosive ions. The composite coatings have been characterized by cyclic voltammetry, Fourier transform infrared (FT-IR) spectroscopy, and scanning electron microscopy (SEM) procedures. The anti-corrosion performance of PNMPY-1SSD/P2MT coated brass has been investigated by potentiostatic and potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) practices in 0.5 M H2SO4 medium. The corrosion assessment of PNMPY-1SSD/P2MT coated brass was noticed to be ~9 times diminished than of uncoated brass, and the efficiency of these protective coatings of this coating is above 90%. The highest effectiveness is realized by the electrochemical deposition of PNMPY-1SSD/P2MT obtained at 1.1 V and 1.4 V potential applied and at 0.5 mA/cm2 and 1 mA/cm2 current densities applied in molar ratio 5:3. The outcomes of the corrosion tests denoted that PNMPY-1SSD/P2MT coatings assure good anti-corrosion protection of brass in corrosive media.

Schottky contact of nano-BiOx thin film synthesized galvanostatically on stainless steel in acetonitrile

In this study, the nanosized-BiOx thin film (mostly Bi2O3 with a trace amount of Bi2O5) is electrochemically synthesized on stainless steel (SS) surface at room temperature. The coating process is carried out using the galvanostatic pulse deposition method in an acetonitrile solution containing bismuth tetrafluoroborate, tartaric acid, tetrabutylammonium hydroxide, and tetrabutylammonium tetrafluoroborate. The structural and morphological characterizations of thin film are performed by XRD, XPS, SEM-EDX, and AFM techniques. Accordingly, α- and δ-Bi2O3-based coating with oxygen vacancies contains a small amount of Bi2O5 on the SS surface. The BiOx thin film exhibits a rough surface with many nano-sized hills homogeneously distributed. Electrical characterization is conducted with electrochemical impedance spectroscopy, current-voltage, and Hall effect measurements. The pseudoresistance with the most drastic change increases with rising potential and decreases again after reaching its maximum value at the open circuit potential. It could be inferred that the composition (oxidation states or oxygen deficiency) of the Bi2O3-based film varies according to the applied potential. The n-type Schottky behavior is observed at the SS/BiOx interface. Furthermore, the n-type SS/BiOx-based Schottky diode tested for endurance shows significant stability over 200 cycles.

Electrodeposition of manganese dioxide coatings onto graphene foam substrates for electrochemical capacitors

Optimisation of electrodeposition routes of birnessite manganese dioxide (MnO2) coatings onto 3D graphene foam substrates enabled greater attainable capacitances. Current pulse deposition method resulted in highest achievable areal capacitance of 530 mF/cm2 under a 10 mA/cm2 current rate, cycling performance with 91% retention after 9000 cycles, as well as improved rate capability when compared to the cyclic voltammetry or galvanostatic deposition. Introduction of oxygen functional groups to the graphene foam added initial pseudocapacitance and accelerated the rate for nucleation and growth of the MnO2 crystal grains, resulting in an areal capacitance of 410 mF/cm2 under a 10 mA/cm2 current rate. However, in this case the increase in specific capacitance was accompanied by sluggish kinetics for charge storage seen via impedance spectroscopy. The charge storage mechanism of the deposited MnO2 films was investigated using in situ Raman microscopy and analysis of peak shifts revealed expansion and contraction of birnessite MnO2, relating to exchange of Na+ and H2O at the MnO2 interface.

Honeycomb structured Co−Ni−Mo alloy deposits prepared from ethylene glycol systems and used as highly active and durable electrocatalysts for HER

One of the most critical challenges in the field of hydrogen production through water electrolysis technique is the design, development and manufacture of electrode materials with low-cost, highly electrocatalytic activity and stability. We employ the galvanostatic deposition technique to prepare the honeycomb structured Co−Ni−Mo alloy electrocatalysts from ethylene glycol (EG) system, in which the honeycomb structure presents highly intrinsic electrocatalytic activity for hydrogen evolution reaction (HER). The electrochemical behavior of Co2+, Ni2+ and Mo6+ reductions and the co-deposition behavior of Co-Ni, Co-Mo, Ni-Mo and Co-Ni-Mo alloys is reported. Benefiting from the composition engineering by alloying with Mo atoms, as well as the simultaneous existence of a suitable honeycomb structure, these Co58Ni23Mo19 deposits obtained at an optimal parameter exhibit prominent electrocatalytic durability and activity with a η10 of 51 mV for HER in a 1.0 M KOH. More importantly, the formation model of the honeycomb structured Co-Ni-Mo alloy deposits is proposed. This work suggests a simple and economical method for the preparation of a 3-dimensional catalytic electrode.

Insights into Chemical Changes Causing Transient Potential Patterns during Cobalt Electrodeposition: An Operando SHINERS Investigation.

Transient potential oscillations in a self-organized system involve a sequence of mass-transfer-limited chemical reactions. Often, these oscillations determine the microstructure of the electrodeposited metallic films. In this study, two distinct potential oscillations have been observed during galvanostatic deposition of cobalt in the presence of butynediol. Understanding the underlying chemical reactions in these potential oscillations is essential for designing efficient electrodeposition systems. Operando shell-isolated nanoparticle-enhanced Raman spectroscopy is deployed to record these chemical changes, and we present direct spectroscopic evidence of adsorbed hydrogen scavenging by butynediol, Co(OH)2 formation, and removal limited by mass transfer of butynediol and protons. The potential oscillatory patterns have four distinguishable segments associated with mass-transfer limitation of either proton or butynediol. These observations improve our understanding of the oscillatory behavior in metal electrodeposition.

Galvanostatic copper deposition on nanostructured carbon screen printed electrodes

Galvanostatic copper deposition on nanostructured carbon screen printed electrodes

Cobalt recovery from spent lithium-ion batteries by leaching in H2SO4-N2 and H2SO4-O2 systems followed by electrochemical deposition

This paper is focused on cobalt valorization from the cathode material of spent lithium-ion batteries (LIBs) by using leaching and electrochemical deposition methods. During the leaching experiments, the degrees of cathode material dissolution in H2SO4-N2 and H2SO4-O2 systems were compared. Maximal degrees of cobalt extraction were 40 % in the former and 47 % in the latter system under following experimental conditions: H2SO4 concentration of 2 mol dm-3, nitrogen/oxygen volumetric flow of 2 L min-1, solid phase concentration of 33 g L-1, and temperature of 85?C. The rate of cobalt extraction from the cathode material in both investigated systems was the most favorable in the first 15 min, after which there was a sudden decrease in the reaction rate. Cobalt from the leaching solution was deposited on a copper substrate by galvanostatic electrochemical deposition with a current efficiency of 84%. The energy consumption was 5.8 kWh kg-1 of deposited Co. The cyclic voltammetry (CV) method was used to determine the potential of cobalt deposition, as well as side reactions taking place in the system. Scanning electron microscopy with energy dispersive spectrometry has shown that during the process of electrochemical deposition agglomeration of cobalt particles occurred (in the shape of cauliflower), while the metal was deposited in its elemental state, which was also confirmed by the results of X-ray diffraction analysis.

Electrodeposited Pd nanoparticles on polypyrole/nickel foam for efficient methanol oxidation

The present work describes the Ni foam (Ni–F)/polypyrrole (PPy)/palladium (Pd) (Ni–F/PPy/Pd) multilayered catalysts via a facile electrochemical technique. Potentiostatic deposition of PPy on the surface of Ni–F is followed by galvanostatic deposition of Pd nanoparticles on Ni–F/PPy acted as supports for electrochemical deposition of Pd nanoparticles. The produced catalysts are utilized for electrocatalytic methanol oxidation in alkaline media. Chronoamperometry (CA), cyclic voltammetry (CVs), and electrochemical impedance spectroscopy (EIS) techniques are used to examine the electrocatalytic performance of Ni–F/PPy/Pd based electrodes for methanol oxidation. The polypyrrole modification on Ni–F leads to an improvement in the electrocatalytic activity of the Ni-F/PPY-Pd catalysts toward methanol oxidation. As an open-pored, porous metal with high electrical conductivity, nickel foam produces a substantial amount of active area during the modification of Pd and polypyrrole, which results in significant catalytic activity and a rapid rate charge transfer reaction kinetics on methanol oxidation. The Ni–F/PPy/Pd10 catalyst exhibits enhanced specific activity than its counterparts and a reduced onset potential for methanol oxidation, as well as a low Tafel slope. Based on these results, Ni–F/PPy/Pd10 is suggested as a good material for the anode in the electrocatalytic oxidation of methanol.