Electrodeposition Of Co Research Articles

Electrochemical Quartz Crystal Microbalance Study on the Electrodeposition of Fe, Co and Fe-Co Alloys

Cobalt-iron alloys are interesting soft magnetic materials which are used for example in magnetic sensors and transducers. They can be obtained by different techniques such as PVD, magnetron sputtering, or casting. One easy and not very expensive way to produce these alloys is the electrochemical deposition technique, which was also chosen in this study.This contribution will describe the electrodeposition of Co, Fe and Fe-Co alloys (Fe70Co30) from an aqueous sulphate-based electrolyte containing boric acid as a buffer and sodium citrate and citric acid besides the metal sulphates. Potentiostatic step experiments and cyclic voltammetry were performed in parallel to electrochemical quartz crystal microbalance. Thus, we could identify the potential at which the deposition of the metals sets in, the mass of the deposited species as well as the current efficiency. We could also extract the partial current due to hydrogen evolution reaction and the partial current due to individual metal or their alloys from the total current density. The morphology and structure of the deposited films were investigated by means of SEM and XRD, respectively. The grain size of the deposits was calculated from the XRD data using Scherrer equation. Addition of citric acid to the electrolyte results in the smaller grain size of the deposited Fe-Co films.

Growth of surfactant-free Au-Co bimetallic atom-bomb cracker-like microstructures: A highly active morphological dependent hybrid electrocatalyst for dioxygen reduction

This paper reports the formation of atom-bomb fire cracker (ABC) like Au-Co heterostructures by attaching folic acid-capped AuNPs (FA-AuNPs) on a glassy carbon (GC) electrode followed by cobalt electrodeposition. The characteristic absorption band at 516 nm from the UV–visible spectrum confirms the AuNPs formation and their average size was ∼6 nm as evidenced from HR-TEM. The AuNPs were then assembled on a GC electrode via 1,6-hexadiamine linker followed by the electrodeposition of Co at various applied potentials and time. XPS spectra of Au-Co clearly revealed the zero valent nature of Au and Co and Co2+ in the bimetallic assembly. The SEM results exhibited the variations in the morphology of Au-Co with respect to the applied potential and time. It was found that the deposition of Co at -0.50 V for 600 s leads to the formation of ABC-like structure only at FA-AuNPs surface. The specific atom-bomb morphology of Au-Co was not obtained at bare GC and citrate-capped AuNPs surfaces, indicating the influence of FA-AuNPs. The Au-Co showed higher electrocatalytic activity towards dioxygen reduction by shifting the onset potential by 230 and 280 mV towards zero respectively than Co and AuNPs alone. The Koutecky-Levich plot confirms the four-electron transfer mechanism of oxygen reduction at Au-Co fabricated electrode.

Improvement on solar selective absorption properties of anodic aluminum oxide photonic crystal films by electrodeposition of silver

Solar selective absorption films based on anodic aluminum oxide (AAO) photonic crystals were prepared by an anodization under periodic current-pulses, subsequently with an alternating current electrodeposition of Co and Ag in sequence. The phase structure, microstructure, and solar selective absorption properties of the Co–Ag electrodeposited film were investigated in comparison with a Co electrodeposited counterpart. Moreover, the stability of the properties against thermal annealing was examined for the two films. A one-dimensional photonic crystal structure was verified for the AAO part in both films, with the first-order photonic bandgap occurring at around 4 μm, while the metals were confirmed to be deposited at the bottom of the AAO part in the form of nanoparticles. For the Co–Ag electrodeposited film, the Ag nanoparticles were deposited over those of Co. The Ag electrodeposition not only was contributive to the solar selective absorption properties, but also substantially improved the stability of the properties against thermal annealing. The Co–Ag electrodeposited film exhibited an infrared emissivity of 0.12, a solar absorptivity of 0.94, and a spectral selectivity of 7.83 before experiencing thermal annealing, while retained a decent spectral selectivity of 6.00 after being annealed in air at 300 °C for 24 h.

Electrodeposition of Ni-Co Alloys from Ionic Liquids and Their Electrocatalytic Properties

Amorphous and nanocrystalline Ni-Co alloys have been deposited on FTO glass in ethylammonium nitrate (EAN), a protic ionic liquid (PIL). In a first step, the physicochemical properties of EAN with Ni2+ and Co2+ salts have been studied as well as the electrochemical behavior of these metal cations in the PIL in order to optimize the electroplating process (Fig. 1). It was shown that when the electrodeposition of Co, Ni and Ni-Co alloys was performed on FTO glass in EAN at 60 ℃ in an oxygen-free environment, nanocrystalline Ni-Co alloys with different atomic ratios were obtained, depending on both the deposition potential and the ion concentration in solution.The electrocatalytic properties of these materials were then investigated towards the hydrogen evolution reaction (HER). It was shown that the addition of Co in Ni-based alloys can promote the HER, and most notably, amorphous Ni-Co alloys show lower overpotential or reaction rate. This work provides a new route to prepare nanocrystalline and amorphous Ni-Co alloys with different ratio in PIL for practical applications in electrocatalysis such as water splitting. Figure 1

Nanostructured Ir-based electrocatalysts for oxygen evolution prepared by galvanic displacement of Co and Ni

Proton exchange membrane (PEM) electrolysers are promising devices to produce hydrogen as a green fuel. Currently, this technology is limited by the sluggish kinetics of the oxygen evolution reaction (OER). In this work, we describe an environmentally safe method for the preparation of Ir oxide thin films (IrO2) for OER. Electrodeposition of Co and Ni was performed in the non-toxic choline chloride:urea deep eutectic solvent (ChCl:urea DES), followed by galvanic displacement reaction (GDR) of Co and Ni by Ir(IV). We evaluated how the GDR conditions, such as the metal replaced (Co or Ni), time and temperature affect both the activity and stability of the deposited IrO2 films on gold substrates. We observed that GDR of Ni at 90 °C induces morphological changes on the IrO2 nanostructures which resulted in higher activity and stability towards OER. We highlight that not only reducing mass loadings of Ir but also tuning the surface morphology and structure controlling the synthesis preparation, as well as investigating the role of the substrate, are key to design more active and stable OER electrocatalysts.

Size Effect in the Rate of Electrodeposition of Co–W Coatings from a Citrate Bath

Size Effect in the Rate of Electrodeposition of Co–W Coatings from a Citrate Bath

Electrodeposition of Ni-Co alloys from neat protic ionic liquid: Application to the hydrogen evolution reaction

Amorphous and nanocrystalline Ni-Co alloys have been deposited on FTO glass in ethylammonium nitrate (EAN), a protic ionic liquid (PIL). The physicochemical properties of EAN with Ni2+ and Co2+ salts have been studied as well as the electrochemical behavior of these metal cations in the PIL in aerated atmosphere. Electrochemical studies showed that the redox reactions of Ni2+ and Co2+ leading to metal deposit on glassy carbon are not reversible in those conditions due to the formation of an oxide film. Conversely, when electrodeposition of Co, Ni and Ni-Co alloys on FTO glass in EAN was performed at 60 °C in an oxygen-free environment, nanocrystalline Ni-Co alloys with different atomic ratios were obtained depending on both the deposition potential and ion concentration in solution. The composition and the morphology of the electroplated alloys were determined by several techniques such as SEM, TEM, XRD and XPS. The electrocatalytic properties of these materials were investigated towards the hydrogen evolution reaction (HER). It was shown that the addition of Co in Ni-based alloys can promote the HER, and most notably, amorphous Ni-Co alloys shows lower overpotential or reaction rate. Up to now, the better electrocatalytic results were obtained with the amorphous Ni51.9Co48.1 alloy, electrodeposited in EAN at high potential (-1.3 V/Ag/Ag+). This work provides a new route to prepare nanocrystalline and amorphous Ni-Co alloys with different ratio in PIL for practical applications in electrocatalysis such as water splitting.

Stainless steel as gas evolving electrodes in water electrolysis: Enhancing the activity for hydrogen evolution reaction via electrodeposition of Co and CoP catalysts

A facile electrodeposition strategy has been used to modify the stainless steel mesh with Co and CoP catalysts (Co-SSM and CoP-SSM) to be utilized as free-standing electrodes for hydrogen evolution reaction (HER) in alkaline media. The electrodeposition parameters have been optimized to achieve the high catalytic activity. The surface morphologies, the crystal phases and compositions have been identified by SEM, XRD and XPS analyses. The XRD results showed that the Co catalyst (Co-SSM) is present in two mixtures of hexagonal and cubic metallic phases, while the incorporation of P into Co in CoP-SSM resulted in the creation of an amorphous phase as detected by XRD and confirmed from XPS. The CoP-SSM electrode exhibited high electrocatalytic activity towards HER with an overpotential of 264 mV vs. RHE compared to 382 mV and 462 mV for Co-SSM and the pristine SSM electrodes; respectively. Moreover, the CoP-SSM electrode exhibited high stability after continues electrolysis at 50 mA cm−2 with only potential increase of 42 mV after 20 h. These results introduce the developed CoP-SSM electrodes as highly active and stable electrodes for the application in alkaline water electrolysis technology for hydrogen production.

A Pt cathode with high mass activity for proton exchange membrane water electrolysis

To reduce the fabrication cost of proton exchange membrane water electrolyzers (PEMWEs), low-loading platinum-based cathodes were fabricated through constant potential (−1.1 VSCE) electrodeposition of Co, galvanic displacement with Pt in K2PtCl4 + NaCl solution, and subsequent chemical (immersion in 0.5 M H2SO4 for 5 min) or electrochemical dealloying (2000 potential cycles at −0.2 to −0.5 VSCE in 0.5 M H2SO4) processes. These simple electrochemical steps produced a bimodal structure of layered Pt/Co/carbon paper (CP) and particulate Pt/CP catalysts on a porous transport layer of carbon fiber. Heat treatment of Co deposits (500 °C for 2 h, H2/Ar atmosphere) prior to Pt displacement was found to strongly affect the stability of Co and the electronic structures of subsequently placed Pt, resulting in high activity (an overpotential of 18.4 mV at −10 mA cm−2) and durability (∼6000 potential cycles) of the electrochemically dealloyed catalyst in hydrogen evolution reaction. A single cell with this catalyst at low cathode Pt loading of 18.4 μg cm−2 further demonstrated excellent performance of 2.39 A cm−2 @ 1.9 V. The cathode Pt mass activity is superior to previous works on other low Pt electrode fabrication methods using pulse electrodeposition or self-terminated electrodeposition, providing a new lower limit of precious metal usage for PEMWE.

(Invited, Digital Presentation) Electrocatalyst and Electrolyte Engineering for Oxygen Evolution in Acidic Media

The slow kinetics of the oxygen evolution reaction (OER) limits the performance of proton exchange membrane (PEM) electrolysers. Only iridium-based oxides are both reasonably active and stable for the OER in acidic electrolytes [1], and high amounts of Ir are needed at the anode of PEM electrolysers. In addition, the lack of stable support materials limits the utilisation of Ir. Designing novel electrocatalysts with enhanced OER activity and stability in acidic media remains a great challenge. In this talk, I will present some recent strategies aiming to understand and engineer the interfacial structure and properties for oxygen evolution electrocatalysis. We have developed self-supported high surface area nanostructured Ir-based networks as highly active electrocatalysts for OER [2]. These networks, prepared by alternating sputtering of Ir and Co, followed by selective Co leaching, show a unique morphology and combine excellent mass activity with promising stability [2]. In addition, our group is working in the development of an easy and affordable method to prepare IrOx catalysts by controlled electrodeposition of Co and Ni in a deep eutectic solvent followed by galvanic displacement [3]. By controlling the conditions during the galvanic displacement, we tune the morphology and thus the electrocatalytic properties for OER. Finally, we have investigated the role of both composition and concentration of the acidic electrolyte (perchloric and sulphuric acid) on the OER electrocatalytic performance of Ir nanoparticles [4]. Our work highlights the key role the electrolyte plays in the performance of Ir-based electrocatalysts during rotating disc electrode measurements.REFERENCES[1] M. Escudero-Escribano et al., Journal of Physical Chemistry B 2018, 122, 947.[2] A.W. Jensen, G.W. Sievers, K.D. Jensen, J. Quinson, J.A. Arminio-Ravelo, V. Brüser, M. Arenz, M. Escudero-Escribano, Journal of Materials Chemistry A 2020, 8, 1066.[3] F.B. Holde, K.N. Dalby, H. Falsig, P. Sebastián-Pascual, M. Escudero-Escribano, in prep., 2022.[4] J.A. Arminio-Ravelo, A.W. Jensen, K.D. Jensen, J. Quinson, M. Escudero-Escribano, ChemPhysChem 2019, 20, 2956.

Electrochemical routes for environmentally friendly recycling of rare-earth-based (Sm–Co) permanent magnets

The consumption of critical raw materials, especially those in permanent magnets of Nd–Fe–B and Sm–Co-type, has significantly grown in the past decade. With predictions on further electrification growing exponentially the demand for these materials will even increase. This implies that efforts in assuring sustainability must involve recycling from secondary resources. In recent years the electrochemical approaches in recycling have been extensively investigated and applied owing to their advantages of high efficiency and selectivity, easy operation, low energy consumption, and environmental friendliness. In this paper, we investigate the Sm2(Co,Fe,Cu,Zr)17 permanent magnet leaching process using the anodic oxidation to be paired with the metal deposition on the cathode. Linear sweep voltammetry was performed from − 0.15 to 1 V versus Pt quasi reference electrode that indicated current peaks that would correspond to some preferential leaching of the crystal phases contained in the magnet. The latter was confirmed using the SEM/EDXS analysis. The continuous leaching of the Sm2(Co,Fe,Cu,Zr)17 magnet was performed at a direct current density of 2, 4 and 8 mA cm−2 at the time period of 0–240, 240–480 and 480–720 min, respectively. The ICP-MS results confirmed the leaching of all the metals from the original Sm2(Co,Fe,Cu,Zr)17 permanent magnet. The concentration of Sm3+, Cu2+, Fe2+ and Zr2+ increases linearly along with the leaching time. Reversely the concentration of Co2+ decreases linearly due to its consumption by electrodeposition of Co, Fe and Cu on the cathode. The presented paired electrochemical process could serve as a starting point for the recycling and recovery of critical raw materials without any acid usage and waste generation.Graphical abstract

Ideally Ordered Anodic Porous Alumina on Si Substrate Prepared by Anodization of Sputtered Al–Mg Thin Film

Anodic porous alumina with an ideally ordered hole arrangement was formed on a Si substrate by nanoimprinting and subsequent anodization. In this process, the arrayed shallow dimples formed by nanoimprinting using a mold act as initiation sites of hole development during the anodization. To realize the precise transfer of the mold patterns to the Al surface during nanoimprinting, we used sputtered Al alloy film as a starting material. This is because the Al alloy with appropriate impurities as a sputtering target can suppress the crystal grain growth during sputtering and allow the formation of Al alloy films with smooth surfaces on the substrate. Dimple arrays with 100 nm intervals could be formed on the flat surface of the Al–Mg film on the Si substrate. Ideally ordered anodic porous alumina with an interpore distance of 100 nm was successfully obtained by subsequent anodization. A Co/alumina composite was also obtained by the electrodeposition of Co into the alumina holes. The obtained samples are expected to be applied to various functional devices requiring an ideally ordered structure on a substrate.

Enhancing the Effectiveness of Oxygen Evolution Reaction by Electrodeposition of Transition Metal Nanoparticles on Nickel Foam Material

Electrochemical oxygen evolution reaction (OER) activity was studied on nickel foam-based electrodes. The OER was investigated in 0.1 M NaOH solution at room temperature on as-received and Co- or Mo-modified Ni foam anodes. Corresponding values of charge-transfer resistance, exchange current-density for the OER and other electrochemical parameters for the examined Ni foam composites were recorded. The electrodeposition of Co or Mo on Ni foam base-materials resulted in a significant enhancement of the OER electrocatalytic activity. The quality and extent of Co, and Mo electrodeposition on Ni foam were characterized by means of scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) analysis.

Electrodeposition of Co in an Amide-Type Ionic Liquid under an External Magnetic Field

Electrodeposition of Co was investigated in an amide-type ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (BMPTFSA), under an external magnetic field. Neodymium magnets were used as a source of the magnetic field, which was parallel to the ionic current during the electrodeposition of Co on a glassy carbon electrode. Potentiostatic cathodic reduction applying –1.6 and –2.0 V vs Ag∣Ag(I) under the magnetic field in BMPTFSA containing Co(TFSA)2 at 25 °C gave nanowire-shaped deposits on the electrode surface. The deposits were found to be composed of Co, which 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 nanowires were further examined by transmission electron microscopy. The lattice fringe corresponding to (111) plane of Co was found in the deposits, indicating the nanowires were composed of metallic Co nanoparticles. Therefore, crystalline Co nanoparticles were considered to be formed in the presence of the magnetic field.

Promoting the formation of Co (III) electrocatalyst with diamond anodes

In this work, the catalytic effect of electrode substrate on the electrochemical oxidation of cobalt (II) using boron doped diamond (BDD) anodes was studied. A significant increase of the Co (III) formation was observed in using BDD coatings on tantalum substrate (91.43% at around 90 min of galvanostatic electrolysis), with respect to the Si-BDD anode, which only attained a poorer Co (III) conversion (8.33%) after applying the same electric charge. Electrochemical impedance spectroscopy showed that the Ta/BDD electrode has a lower charge-transfer resistance for the Co (II)/Co(III) metallic pair and the process is controlled by diffusion of cobalt towards the electrode surface, due to its rapid adsorption at the interface. This was further confirmed by cyclic voltammetry (CV) where the electrodeposition of Co (II) on the electrode surface is obviously significant if we compare it with that of Si/BDD anode. This difference in the electrode behavior, caused by the substrate on which the diamond coating is deposited, opens a line of research to improve the efficiency of mediated electrolytic treatments based on the use of Co, with important industrial applications in the treatment of many pollutants including volatile organic compounds (VOCs).

Additive-free electrodeposition of cobalt on silicon from 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid

This study describes the use of the ionic liquid (IL), 1-butyl-3-methylimidazolium tetrafluoroborate ([BMI][BF4]) as an efficient and environmental-friendly electrolyte to obtain nanocrystalline cobalt (Co) electrodeposits on a silicon substrate without any additives. Co films were successfully electrodeposited from CoCl2 dissolved in a Lewis basic [BMI]Cl-[BF4] IL system, at 25 °C and 50 °C. Electrochemical techniques were employed to evaluate electrochemical parameters and to investigate the nucleation/growth mechanism involved. Results show that the electrodeposition of Co, under both temperatures, takes place by three-dimensional instantaneous nucleation with diffusion-controlled growth. Considerably small diffusion coefficients of the dissolved Co(II) species were found (1.60 × 10−10 cm2.s−1 and 8.21 × 10−10 cm2.s−1 for 25 °C and 50 °C, respectively). Chemical composition, surface morphology and crystallinity of the electrodeposits were characterized by energy-dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM) and X-ray diffraction (XRD), respectively. High-quality and purity metallic cobalt electrodeposits were obtained. Co films were compact, smooth, bright and adhering to the substrate, exhibiting hcp single-phase structure with nanosized metallic particles of Co. Elevated current efficiencies (94.8% and 96.8% for 25 °C and 50 °C, respectively) were found, showing that [BMI][BF4] IL shows a large potential for the Co electrodeposition on a silicon substrate.

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).

Preparation and Characterization of Electrodeposited Co/p-Si Schottky Diodes

Schottky diodes were prepared by photoinduced electrodeposition of Co on p-Si, probing the influence of different concentrations of CoSO4 (26 and 104 mM) in the electrolyte on the electrical properties of the metal-semiconductor interface. Current density versus voltage (JxV) and capacitance versus voltage (CxV) measurements were performed in diodes with different Co thicknesses to obtain the barrier heights and ideality factors. Atomic force microscopy (AFM) and vibrating sample magnetometry (VSM) were additional techniques used to determine the surface morphology and the magnetic response. Devices with improved electrical properties were observed by increasing the thickness of the metal, i. e., saturation currents with values of about 0.1 mA.cm-2, ideality factors close to 1.19 and barrier heights of about 0.65 eV were determined.

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.

Improving adhesion strength of sol-gel coating on CoCrMo by electrochemical pretreatment

CoCrMo is commonly used as the femoral head material in the artificial hip joint. In order to increase the wear and corrosion resistance of the femoral head, the use of ceramic coating has been reported. Besides the tribological properties of the coating, coating adhesion is of paramount importance in prolonging the service life of the implant. The present study aims at improving the adhesion of ZrO2 sol-gel coating on CoCrMo substrate via pretreatment of the substrate. Two types of pretreatment, namely, electro-etching and electrodeposition of Co, were attempted to create different surface topography on the substrate. It is found that electrodeposition under appropriate conditions (current density of 100 mA/cm2 for 150 s) could effectively increase the adhesion strength, by about 37% and 83% for the load of first crack (Lc1) and the load of breakthrough (Lc2), respectively. The improvement could be attributed to the creation of a densely populated “prolate spheroids”, which provided an increased contact area for bonding and mechanical interlocking.