Electrodeposition Of Cobalt Research Articles

Electrodeposition of Cobalt in a Pyrrolidinium-Based Ionic Liquid Under a Magnetic Field

Cobalt (Co) is well-known as a hard-magnetic material for its tailorable magnetic properties. Nowadays, a pyrrolidinium-based ionic liquid, composed of 1-butyl-1-methylpyrrolidinium (BMP+) and bis(trifluromethylsulfonyl)amide (TFSA–), has drawn more attention for the electrodeposition of various transition metals because of its wide electrochemical potential window, acceptable ionic conductivity, and high stability against moisture. Although the redox reaction of Co species has been reported in BMPTFSA, the electrochemical behavior of Co species under a magnetic field has not been explored in this ionic liquid.1-3 In this study, the electrodeposition of Co has been performed in BMPTFSA under a static magnetic field. Co(TFSA)2 was prepared by the reaction of CoCO3 with HTFSA. A Teflon made, double compartment cell was used for the electrochemical measurements using a glassy carbon (GC) as a working electrode, a platinum mesh as a counter electrode, and a silver wire immersed in BMPTFSA containing 0.1 M AgCF3SO3 as a reference electrode. A neodymium magnet (NdFeB) was attached to the back of the GC electrode. The diameter of the magnet was 6 mm and the magnetic flux density was 530 mT. Potentiostatic cathodic reduction applying –1.6 and –2.0 V was conducted under the magnetic field in BMPTFSA containing Co(TFSA)2 at 25 °C. Nanowire-shaped deposits were obtained on the GC electrode after the electrodeposition at both potentials. The presence of Co in the deposits was confirmed by energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. However, no diffraction peak was observed in the deposits by X-ray diffraction. The deposits were further examined by transmission electron microscopy. The lattice fringe corresponding to (111) plane of Co was found in the deposits, indicating the deposits were composed of metallic Co nanoparticles.References(1) R. Fukui, Y. Katayama, and T. Miura, Electrochemistry, 73, 567 (2005).(2) Y. Katayama, R. Fukui, and T. Miura, J. Electrochem. Soc., 154, D534 (2007).(3) Y. Katayama, R. Fukui, and T. Miura, Electrochemistry, 81, 532 (2013).

Amperometric assay of hydrazine utilizing electro-deposited cobalt hexacyanoferrate nanocrystals on graphene oxide sheets

In-situ electrochemical deposition of cobalt hexacyanoferrate (CoHCF) on graphene oxide (GO) and its application for the electrocatalytic hydrazine determination in real samples are described in this research study. Co2+ is immobilized on GO and the resulting material, GO-Co2+ is coated on the surface of glassy carbon (GC) electrode. The fabricated electrode (GC/GO-Co2+) is subjected to a continuous potential cycling in the range of 0.0–1.0 V which results in the formation of a thin CoHCF film on the surface of GO coated on the GC electrode (abbreviated as GC/GO-CoHCF). The synthesized GO-CoHCF composite material is characterized by Fourier transform infrared and scanning electron microscopy. GC/GO-CoHCF electrode electrocatalytically oxidizes hydrazine at low overpotential (0.63 V) and this phenomenon is subsequently utilized for the sensitive determination of hydrazine in aqueous solutions. It exhibits a wide linear calibration range (0.1–400 µM), high sensitivity (0.93 µA µM−1 cm−2) and low limit of detection (17.5 nM) for the determination of hydrazine. Further, this electrode is employed for hydrazine determination in real samples.

Electrodeposited black cobalt selective coatings for application in solar thermal collectors: Fabrication, characterization, and stability

We report on the electrodeposition of nickel/black cobalt selective coatings, and evaluate the performance stability as a function of the substrate material, the temperature of heat treatments, and under accelerated weathering conditions. The black cobalt absorber material is shown to be stable up to 750 °C, and the performance stability for a stainless steel substrate with a nickel/black cobalt selective coating after 200 h at 300 °C is demonstrated, with a solar absorptance of 95% and thermal emittance of 7% (at 100 °C). The galvanostatic electrodeposition process has been scaled up to collector size, and is demonstrated both for a flat plate and a tubular substrate. A copper flat plate of 193 cm × 12 cm connected to a riser tube was coated, and a single-fin solar thermal collector was evaluated under realistic outdoor conditions. The collector produced essentially the same amount of heat as an identical reference collector with a commercial TiNOX selective coating. In addition, the coating was applied to a copper tube for a 3 m parabolic trough collector . The selective coating is hydrophobic and withstands an accelerated weathering test, illustrating the viability of black cobalt electrodeposition for the fabrication of solar collectors for low and high temperature applications.

Investigation of polyvinylpyrrolidone as an inhibitor for trench super-filling of cobalt electrodeposition

Polyvinylpyrrolidone (PVP) is studied in this paper as an inhibitor of cobalt electrodeposition. The suppression effect of PVP was analyzed through electrochemical methods, including cyclic voltammetry (CV) and galvanostatic measurements (GM) tests. It is indicated that PVP effectively suppresses the electrodeposition of cobalt and chloride ion accelerates this suppression. Further experiments verify that PVP inhibits the deposition of cobalt through the adsorption on the electrode surface. Quantum chemical calculations were employed to calculate the molecular orbitals of PVP and the electrostatic potential (ESP) energy of the involved molecules. The simulation results imply that the amide group acts as the main electrophilic attack region and facilitates nucleophilic reactions to bond with cobalt. High aspect ratio trench filling on silicon wafer was achieved with the addition of PVP, which confirms that PVP is an applicable inhibitor for the practical electrodeposition of cobalt filling. The mechanism of cobalt trench filling was proposed to explain the role of PVP in the electroplating filling. Besides, crystalline and morphological characterizations reveal that PVP is able to inhibit the specific crystal growth of cobalt, especially the growth of 220 crystal plane, affect the crystal morphology of cobalt and improve surface compactness.

Discerning the oscillatory electrochemical response during electrodeposition of cobalt in the presence of but-2-yne-1,4-diol

We present a new observation of electrochemical oscillation during the reduction of Co2+ from sulfate solution in the presence of but-2-yne-1,4-diol (butynediol) as an additive. Cyclic voltammetry, hydrodynamic voltammetry at galvanostatic condition, and electrochemical impedance spectroscopic studies suggest that the electrochemical oscillation observed was a relaxation type and was the manifestation of adsorbed hydrogen formation by electrochemical reduction of protons on cobalt and their chemical removal by semi-hydrogenation of butynediol to butenediol during the initial stages of electrodeposition.

Nickel/Cobalt nanoparticles for electrochemical production of hydrogen

The electrolytic production of hydrogen (POH) from alkaline water electrolysis is at the forefront of technology for alternative energy sources of the future. The present work evaluates the improvement of electro-catalytic activity (ECA) on Ni electrodes for the POH by electrodeposition of cobalt (Co). Tests were conducted in alkaline solution and the ECA of Ni and Ni–Co electrodes for the POH were compared using alternative and direct current techniques. Tafel polarization tests exemplified a significant improvement in the ECA of the bimetallic electrode (Ni–Co) compared with the Ni-electrode. Besides, the bimetallic electrode required less input overpotential energy (η) for the given POH rate under constant current density. Electrochemical impedance spectroscopy (EIS) revealed a significant increase in the number of electrochemical active sites and changed the surface morphology following the electrodeposition of Co over Ni electrodes.

Electrodeposition of pore-confined cobalt in metal–organic framework thin films toward electrochemical H2O2 detection

In this study, cobalt is electrodeposited within solvothermally grown thin films of a zirconium-based metal–organic framework, MOF-808, to obtain electrochemically active cobalt confined in the pore of MOF-808 crystals. With the help of the highly porous but electrically insulating MOF-808 thin film and a step-wise electrodepositing technique, cobalt can be mainly deposited within the pore of MOF-808 crystals. The resulting Co@MOF-808 thin film is applied for electrochemical H2O2 sensor in aqueous electrolytes, and its electrocatalytic activity toward H2O2 significantly outperforms that of the electrodeposited cobalt on a bare substrate. The electrochemical behavior of Co@MOF-808 thin films and the corresponding electrocatalytic mechanism toward H2O2 are investigated. The material is further used for amperometric H2O2 detection, and a sensitivity, limit of detection, and linear range of 382.27 μA/mM-cm2, 1.3 μM, and 10–450 μM can be achieved, respectively.

Edge electrodeposition effect of cobalt under an external magnetic field

The dynamic changes in the concentration and diffusion layer at the Ni/CoCl2 solution interface were studied by digital holography during the electrodeposition of cobalt on a nickel electrode in 0.15 M CoCl2 with and without an external magnetic field. Edge electrodeposition was observed under the condition of a non-uniform magnetic field on the electrode. The concentration distribution at the interface was consistent with the intensity of the magnetic field distribution. However, there was no “edge electrodeposition” during the electrodeposition of cobalt on copper electrodes under magnetic field conditions. It was proposed that the edge electrodeposition of cobalt on a nickel electrode under magnetic field conditions was mainly caused by the magnetic gradient force and the Lorentz force around the edges of the magnetised electrode.

Effect of Magnetic Co–CoO Particles on the Carrier Transport in Monolayer Graphene

Electrodeposition of cobalt on monolayer graphene synthesized by chemical vapor deposition produces Co–CoO/graphene composite structures, which is accompanied by increases in the electrical resistance and magnetoresistance. We show that the observed magnetoresistance effect is caused by two competing contributions: negative (NMR) and positive (PMR) magnetoresistance. In weak magnetic fields, the NMR is described by quantum localization correction to the Drude model of conductivity in graphene. The enhancement of PMR observed in strong magnetic fields is related to the Lorentz mechanism in Co–CoO particles.

Proton Sensitive Additive for Cobalt Electrodeposition

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

The Multi-Functional Role of Boric Acid in Cobalt Electrodeposition and Superfill

Although alternative metals such as cobalt are becoming increasingly important as candidates for filling interconnects, questions remain regarding the role of boric acid, one of the primary bath components, in the electroplating process. This work demonstrates that boric acid has multiple functions in cobalt electroplating and superfill. Raman spectroscopy was used to determine speciation of boric acid in solution as a function of concentration and pH. Combining this with titration experiments, it was found that polyborate formation coincides with an increase in buffering capacity in the range of pH that is typical for cobalt electroplating. Atomic force microscopy and secondary ion mass spectrometry confirmed the correlation between hydroxide/oxide in the deposited film and the amount of boric acid in solution. Electrochemical experiments demonstrated that boric acid adsorbs to the electrode surface under certain conditions. Interconnect fill quality was also shown to be directly related to boric acid concentration. Boric acid is shown to be a necessary bath component due to its role in pH buffering and surface adsorption, affecting both blanket film plating and superfill of interconnects in the presence of a suppressor.

A cobalt–phosphorus nanoparticle decorated N-doped carbon nanosheet array for efficient and durable hydrogen evolution at alkaline pH

In 1.0 M KOH, Co–P@NC/CC, prepared by electrodeposition of cobalt–phosphorus nanoparticles on a polyimide derived N-doped carbon nanosheet array supported on carbon cloth, shows outstanding catalytic activity with the demand of an overpotential of 75 mV to drive 10 mA cm−2.

Investigation of Supercapacitive Behaviour of Electrodeposited Cobalt Oxide Thin Film by Potentiostatic Mode

Investigation of Supercapacitive Behaviour of Electrodeposited Cobalt Oxide Thin Film by Potentiostatic Mode

Effect of cobalt deposition on Ni anodes for alkaline membrane water electrolyser

In this work, the performance of nickel-based anodes in an alkaline membrane electrolysis cell was investigated. In particular, the effect of the presence of a very low quantity of electro-deposited cobalt on a porous Ni electrode directly interfaced with a commercial anionic membrane was evaluated. The modified Ni–Co structure was investigated by XRD, SEM, EDS and XPS, and showed different characteristics compared to the starting Ni structure with a surface ratio of Co equal to Ni. The catalytic activity for the oxygen evolution reaction (OER) at the electrode/membrane interface increased considerably compared to pure nickel and reached the same level as a Ni/Pt reference electrode. We believe that this methodology, if further optimized, could open a new way to find an effective improved doping of the nickel anode able to work with alkaline membrane electrolysers.

Electrochemical fabrication of cobalt films in a choline chloride–ethylene glycol deep eutectic solvent containing water

The electrodeposition of cobalt from alternative electrolytes, including ionic liquids and deep eutectic solvents (DES), has become a topic of great interest to the scientific community, with a significant impact in both academic circles and in the development of commercial industrial electrochemical processes. However, very few studies have considered the effects of water on the electrodeposition of metals from deep eutectic solvents. In this work, the electrodeposition of Co from a choline chloride (ChCl) ethylene glycol (EG)-based deep eutectic solvent (DES) containing 10%, 20% and 30% water has been studied, and for the first time a uniform and bright Co deposit has been obtained when the deposition was achieved from an electrolyte containing 20% water. The speciation of Co in a mixed 1:2 ChCl:EG-based liquid (Ethaline 200) has been studied in both the absence and presence of water. The conductivities of the Co electrolyte were increased with increasing amounts of water. The electrochemical properties of the Co electrolytes have been studied using cyclic voltammetry, where it was found that the redox peak current gets larger and shifts in a positive direction when water was included in the Co solution. The resultant surface morphologies, topography, and roughness of the Co deposits were revealed by scanning electron microscopy (SEM) and atomic force microscopy (AFM), which demonstrated that a highly uniform and smooth cobalt coating had been produced when the deposition occurred in Ethaline 200 containing 20% water.

Effects of pH and annealing on microstructure and magnetic properties of fabricated Co100-xWx nanowire arrays by AC electrodeposition

Co100-XWX (0 ≤ Χ ≤ 8) nanowire arrays with mean diameters of ~33 nm were synthesized by alternating current electrodeposition of Cobalt and Tungsten into template of anodic aluminum oxide. Effects of W concentration, pH and annealing process on magnetic properties and crystal structure of the fabricated nanowires were studied using Scanning electron microscopy, Energy dispersive X-ray spectroscopy, X-ray diffraction, and alternating gradient force magnetometer. The obtained results demonstrated that the crystal structure of prepared nanowires was hcp and fcc and a mixture of both, and the magnetic parameters such as coercivity and squareness (Sq = Mr/Ms) of nanowire arrays decreased with increasing the tungsten content and pH. For the study the effect of annealing temperature on the nanowire magnetic properties, the fabricated nanowires were annealed at different temperature (300 °C–600 °C). It is observed that the coercivity for all nanowire arrays with the different value of W content and pH increases with annealing temperature and the maximum variation is related to Co97W3 nanowire at pH = 3, which is explained by shape and magnetocrystelline anisotropy that is discussed in detail.

Effect of Cl– and $${\text{SO}}_{4}^{{2 - }}$$ Ions on Electrodeposition of Cobalt from Acidic Gluconate Solutions

A role of anions in potentiostatic electrodeposition of cobalt from acidic gluconate solutions was investigated. Equilibrium distribution of soluble species in the solutions was calculated and compared with absorption spectra. Cyclic voltammetry and potentiostatic measurements confirmed that cathodic process was inhibited mainly by free sulfate ions. Improved buffer capacity of gluconate baths by addition of sulfate ions protected against contamination of metal deposits by products of cobalt salt hydrolysis. Mathematical models of metal nucleation were tested indicating progressive mode responsible for the formation of the metal phase. Diffusion coefficients of cobalt species were also calculated using various approaches. Thickness, morphology and structure of cobalt deposits as well as cathodic current efficiency were also discussed.

Ultrasound-assisted pulse electrodeposition of cobalt films

Pulse electrodeposition of cobalt was conducted in a sodium saccharin contained sulfate bath under silent or insonated conditions. The effects of pulse duty cycle, pulse frequency and ultrasonic agitation on the crystallographic structure and surface morphology of cobalt deposits were studied. All deposits obtained have a hexagonal close-packed structure, with its basal plane preferentially aligned parallel to the substrate surface. With the increase in duty cycle, texture coefficient for (100) plane increased whether ultrasonic agitation was imposed or not, while the imposition of ultrasonic agitation clearly decreased the texture coefficient for (100) plane. A finer-grained and smoother cobalt electrodeposit was obtained at 62.5 Hz and 25% duty cycle under insonated condition. To understand the roles that these operating parameters played in the electrodeposition, chronopotentiometry and linear sweep voltammetry were used to record the cathodic potential in cobalt deposition and hydrogen evolution current, respectively, which were associated with the morphological and structural change of cobalt deposits. Transmission electron microscopy was also employed to investigate the microstructure and crystal defect of cobalt films. A high density of stacking faults was detected in the cobalt films by high-resolution transmission electron microscopy.

Surface Engineering of 3D Gas Diffusion Electrodes for High‐Performance H2 Production with Nonprecious Metal Catalysts

AbstractIn this work, a methodology is demonstrated to engineer gas diffusion electrodes for nonprecious metal catalysts. Highly active transition metal phosphides are prepared on carbon‐based gas diffusion electrodes with low catalyst loadings by modifying the O/C ratio at the surface of the electrode. These nonprecious metal catalysts yield extraordinary performance as measured by low overpotentials (51 mV at −10 mA cm−2), unprecedented mass activities (>800 A g−1 at 100 mV overpotential), high turnover frequencies (6.96 H2 s−1 at 100 mV overpotential), and high durability for a precious metal‐free catalyst in acidic media. It is found that a high O/C ratio induces a more hydrophilic surface directly impacting the morphology of the CoP catalyst. The improved hydrophilicity, stemming from introduced oxyl groups on the carbon electrode, creates an electrode surface that yields a well‐distributed growth of cobalt electrodeposits and thus a well‐dispersed catalyst layer with high surface area upon phosphidation. This report demonstrates the high‐performance achievable by CoP at low loadings which facilitates further cost reduction, an important part of enabling the large‐scale commercialization of non‐platinum group metal catalysts. The fabrication strategies described herein offer a pathway to lower catalyst loading while achieving high efficiency and promising stability on a 3D electrode.

Determination of cathode current efficiency for electrodeposition of ferromagnetic cobalt nanowire arrays in nanochannels with extremely large aspect ratio

Cathode current efficiency for the electrodeposition of cobalt from an acidic aqueous solution, which took place in anodized aluminum oxide (AAO) nanochannels with an average diameter of ca. 25 nm, was determined by Faraday’s first law of electrolysis. The electrodeposited metallic cobalt crystals were grown as an array of nanowires embedded in the nanochannels. The amount of charge consumed for the electrochemical reduction in the nanochannels was estimated considering the time dependence of the cathode current during the electrodeposition of the cobalt nanowires. Meanwhile, the volume of electrodeposition on the cobalt nanowires was determined from the saturated magnetic moment of the nanowires, which was obtained from the magnetization curves. The cathode current efficiency for the electrodeposition of the cobalt nanowire arrays remained at a high level (over 75%) in the cathode potential ranging from −0.70 V to −0.85 V vs. Ag/AgCl. At the cathode potential of −0.80 V, the cathode current efficiency reached 97%. The texture coefficient TC(0 0 2) of the cobalt nanowire arrays increased as the cathodic overpotential for the electrodeposition of cobalt decreased. Due to the extremely large aspect ratio (more than 1000), the cobalt nanowire arrays were spontaneously magnetized in the direction parallel to the long axis of the nanowires. With increasing TC(0 0 2), the coercivity and squareness of the cobalt nanowire arrays also increased up to ca. 1.6 kOe and 0.8, respectively, at room temperature.