Pulse Current Electrodeposition Method Research Articles

Microstructure, hardness, and tribological properties of Ni-Co/ SiO2 nanocomposite coating produced through pulsed current electrodeposition

This study investigates the development of Ni-Co/SiO2 nanocomposite coatings on mild steel surface using pulsed-current electrodeposition method. The effects of incorporating SiO2 nanoparticle and varying its concentration on the coatings' microstructure, microhardness, wear resistance, and frictional properties were assessed using field-emission electron microscopy, X-ray diffraction, Vickers microhardness testing, and dry sliding wear tests. The results indicated that the coatings exhibited two-phases of Ni-Co solid solution (α) with a face-centered cubic (FCC) crystal structure and hexagonal Co, a refined crystallite size of approximately 31 nm for Ni-Co and about 25 nm for Ni-Co/SiO2, along with a colony-like morphology that did not show any preferred growth direction. The amount of Ni-Co solid solution increased with the addition of SiO2 nanoparticles. The composite coatings demonstrated enhanced microhardness of 581 HV, which is 52 % greater than that of the Ni-Co coating, as well as improved wear resistance and a reduced friction coefficient compared to the unreinforced alloy coating. However, higher SiO2 content adversely impacted the tribological properties due to nanoparticle agglomeration. Analysis of the worn surfaces revealed a transition from abrasive wear to oxidative wear with increasing applied force for the coatings.

Binder-free copper manganese sulfide nanoflake arrays electrodeposited on reduced graphene oxide-wrapped nickel foam as an efficient battery-type electrode for asymmetric supercapacitors

In the current study, 2D interconnected copper manganese sulfide (CMS) nanoflake arrays are successfully electrodeposited on nickel foam (NF) and reduced graphene oxide-coated NF (NF/rGO). A pulsed current electrodeposition method is used to prepare a uniform and homogeneous coverage of rGO on NF. By using rGO as a conductive carbon-based template, an ultrathin nanoflake structure of CMS with smaller dimensions and higher electrochemically active surface area (ECSA) is achieved. The results reveal the battery-type behavior of the as-synthesized CMS electroactive materials. At a current density of 5 A g−1 this electrode delivers a significant specific capacity of 667 C g-1 and maintained a considerable proportion of its initial capacity, with a retention value of 83.2 % even after undergoing 3000 charge/discharge cycles. In addition, an asymmetric supercapacitor is fabricated by setting up the synthesized NF/rGO/CMS sample as the positive electrode and activated carbon as the negative electrode. The constructed device not only delivers an impressive energy density of 63.3 Wh kg-1 accompanied by an outstanding power density of 11214.5 W kg−1, but also exhibits a considerable cycling durability, enduring only a 12 % decline in specific capacitance after 3000 charge/discharge cycles at a current density of 5 A g−1.

Electrodeposition of nanocrystalline Ni and NiCr alloy coatings: Effects of Cr content on microhardness and wear resistance improvement

The safety and reliability of high-speed trains depend on the brake disc. In order to improve the lifetime of brake disc and reduce the waste of resources, a coating with higher microhardness and well wear resistance is urgently needed. The effect of chromium content on the microstructure, microhardness and wear resistance of NiCr coating has been studied. Nano-crystalline Ni and NiCr coatings with superior mechanical properties were successfully prepared on the 30CrNiMo steel substrate by pulse current electrodeposition method. The inclusion of formic acid and sodium citrate was found to significantly expedite the co-deposition of Ni and Cr. The NiCr coatings with various Cr contents were prepared at current densities ranging from 200 to 300 mA/cm2. These coatings significantly enhance microhardness and wear resistance of the substrate. The microhardness of the NiCr coating increased to 603 HV, outperforming pure Ni coating by 119 HV. Additionally, the wear rate of the NiCr coating decreased by 50% at a load of 10 N in comparison to the Ni coating. The high microhardness is attributed to grain refinement and solution strengthening. This study successfully addresses the challenges associated with electrodepositing Ni-based coatings on 30CrNiMo steel substrate and lays a theoretical foundation for the utilization of Ni-based coatings to enhance the tribological properties of materials used in high-speed train brake disc.

Pulsed current electrodeposition of gold nanostructures on ITO: Control of particle density and optical transmission

With the advance in the plasmonics and metamaterials research field, it has become increasingly crucial to fabricate thin Au metal films cost-effectively and reliably. Here, we study the deposition of gold nanostructures onto the ITO surfaces, using the pulsed current electrodeposition (PED) method, with a pre-seeding step. It was demonstrated that Au nanostructure (AuNS) particle lateral sizes, when deposited onto ITO surfaces, are influenced by deposition current. The lateral size of the particles was found to affect the AuNS density and final form of the film. The study's findings also show that dense films (c.a. 75 %) of Au nanostructures with a thickness of around 5 nm can be formed using the PED method with an optimum current density of 2 A/dm2. Furthermore, the AuNS density has been shown to have a strong influence upon the resulting electrical conductivity and transmittance of the films in the visible and near-infrared wavelength.

Pulse Electrodeposited Super-Hydrophobic Ni-Co/WS2 Nanocomposite Coatings with Enhanced Corrosion-Resistance

The hydrophobicity and corrosion resistance of composite coatings can be effectively improved by changing the electrodeposition method and adding inorganic nanoparticles. In this work, the incorporation of WS2 nanoparticles significantly increased the surface roughness of Ni-Co coatings. The best hydrophobicity and corrosion resistance of the Ni-Co/WS2 nanocomposite coatings (water contact angle of 144.7°) were obtained in the direct current electrodeposition mode when the current density was 3 A/dm2 and the electrodeposition time was 50 min. Compared with direct current electrodeposition, the pulsed current electrodeposition method was more conducive to improving the electrodeposition performance of the nanocomposite coatings. Under the conditions of a current density of 3 A/dm2, pulse duty cycle of 70%, and pulse frequency of 1000 Hz, the nanocomposite coatings reached a superhydrophobic state (water contact angle of 153.8°). The nanocomposite coatings had a slower corrosion rate and larger impedance modulus in this state, and thus the corrosion resistance was superior. The wetting state of the Ni-Co/WS2 nanocomposite coating surface was closer to the Cassie–Baxter model. The protective air layer formed by the layered rough microstructures significantly reduced the actual contact area between the liquid and the substrate, achieving excellent hydrophobic and corrosion resistance properties.

Pulse electrodeposited FeCoNiMnW high entropy alloys as efficient and stable bifunctional electrocatalysts for acidic water splitting

High entropy alloys, possessing unique advantages of atomic scale synergy between multi-constituents, can be suitably designed to fulfill requirements of both activity and stability. Herein, a pulse current electrodeposition method is developed to grow a high entropy FeCoNiMnW alloy (H-FeCoNiMnW) in-situ on carbon papers to serve as an efficient robust bi-functional catalyst for acidic electrolytic water splitting. It exhibits an extraordinarily low overpotential of 15 mV and a serviceable overpotential of 512 mV for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively, both at 10 mA cm−2. The H-FeCoNiMnW//H-FeCoNiMnW couple delivers a current density of 10 mA cm−1 at 1.76 V for overall water splitting, and exhibits outstanding stability, a less than 10% increase in cell voltages after a 6-day operation. Tungsten in H-FeCoNiMnW forms a surface protection oxide layer during the water splitting, rendering the outstanding catalytic stability of H-FeCoNiMnW in acidic media.

The effect of pulse current density on the microstructure, magnetic, mechanical, and corrosion properties of high-entropy alloy coating Fe–Co–Ni–Mo–W, achieved through electro co-deposition

This paper describes the preparation of novel FeCoNiMoW high-entropy alloy coatings using the pulse current electrodeposition method and the effect of pulse current densities of 2, 6, and 10 A/dm2 on the coatings' characteristics. XRD, TEM, EDS, and FESEM were used to perform phase, elemental, and morphological evaluations, respectively. The coatings’ microhardness, magnetic, wear, and corrosion properties were also investigated. The results confirmed the formation of FeCoNiMoW alloy coatings with high entropy. When the current density increased, the morphology changed from a dome to a cauliflower structure. The coexistence of amorphous and nanocrystalline phases was demonstrated by XRD and TEM. Small coercivity (11 Oe-18 Oe) was achieved due to the unique microstructure. The lowest coercivity (11Oe), highest hardness (682 HV), highest wear resistance (COF= 0.5), and highest corrosion resistance (icorr = 3.2 μm/cm2) were obtained at a current density of 6 A/cm2.

Enhanced Electrocatalytic CO2 Reduction of Bismuth Nanosheets with Introducing Surface Bismuth Subcarbonate

The electrocatalytic CO2 reduction reaction (CO2RR) into hydrocarbon products is one of the most promising approaches for CO2 utilization in modern society. However, the application of CO2RR requires optimizing state-of-the-art catalysts as well as elucidating the catalytic interface formation mechanism. In this study, a flower-like nano-structured Bi catalyst is prepared by a facile pulse current electrodeposition method wherein the morphologies could be accurately controlled. Interestingly, nano-structured Bi is inclined to generate Bi2O2CO3 in the air and form a stable Bi2O2CO3@Bi interface, which could enhance the CO2 adsorption and conversion. In-situ Raman spectroscopy analysis also proves the existence of Bi2O2CO3 on the electrode surface. In a practical CO2 reduction test by a flow-cell reactor, the Bi2O2CO3@Bi electrode delivers a high faradaic efficiency of the CO2 to formate/formic acid (~90%) at −1.07 V vs. reversible hydrogen electrode (RHE) with no obvious decay during more than a 10 h continuous test. The introducing surface Bi2O2CO3 in nano-structured Bi supports a promising strategy as well as facile access to prepare improved CO2RR electrocatalysts.

Efficient and clean manganese electrowinning in an anion-exchange membrane electrolyzer by pulse current electrodeposition method

Manganese electrolysis experiments were carried out in an anion-exchange membrane (AEM) electrolyzer employing pulse current (PC) to develop a novel approach for Mn electrowinning. The effects of pulse frequency, duty radio, average cathodic current density, SeO2 concentration and electrolysis time on electrowinning indices were investigated. The morphology, crystalline structure, element distribution and chemical composition of Mn deposits were analyzed employing field emission scanning electron microscopy, X-ray diffraction, electron probe microanalysis, inductively coupled plasma/optical emission spectroscopy and energy dispersive spectroscopy. The experimental results indicated that the electrolysis conditions affected the surface morphology in varying degrees, while all the Mn deposits showed α-Mn structure. By optimizing the electrolysis conditions, the mass transfer limitation of Mn2+ was significantly relieved, the deposition of metallic Mn was obviously improved, and the current efficiency (CE) of 86.45% and the specific energy consumption (SEC) of 4284 kW h t−1 were obtained after electrowinning for 12 h. Compared with the traditional electrowinning technology, the CE increased by about 15%, the SEC declined by about 23% and the per unit yield was promoted by about 56% after employing the approach proposed in this work, which would realize a significant reduction in the waste and pollutant generated during the electrolytic manganese metal production process. The approach of Mn electrowinning in an AEM electrolyzer by PC electrodeposition is recommended as an efficient and clean way.

Comparative Study of Ni-Sn Alloys Electrodeposited from Choline Chloride-Based Ionic Liquids in Direct and Pulsed Current

This work presents, for the first time, the electrodeposition of Ni-Sn alloys in pulse current, from deep eutectic solvents (choline chloride: ethylene glycol eutectic mixture). Additionally, in this study, we report a comparison of the electrodeposition methods known as pulse and direct current. The elemental composition of the films, evaluated from EDX, remained almost constant independently on the electrodeposition parameters. The XRD data revealed the presence of the NiSn metastable phase, which has been confirmed by DSC analysis. This phase shows a nanocrystalline structure with crystallite sizes between 12 and 20 nm. The use of pulse current electrodeposition method has led to an improvement of alloys’ mechanical properties. Moreover, by controlling the electrodeposition parameters, we succeeded in tuning the mechanical properties of the coatings prepared through the PC method. We showed that the hardness parameters exhibited by the Ni-Sn alloys are strongly dependent on their crystallite sizes.

Pulse current electrodeposition of manganese metal from sulfate solution

In this study, pulse current (PC) electrodeposition method was successfully introduced to the process of manganese electrodeposition. The results showed that, due to the transient high current density, pulse electrolysis can rise cathode overpotential (larger 90–100 mV than the direct current (DC)) at the same current density. And high cathode overpotential can significantly suppress the hydrogen evolution and improve the reaction rate of manganese deposit. At the same time, the higher cathode potential promotes crystal nucleus formation, which tends to get smooth manganese metal product surface. Through electrolysis experiment, it was found that when the pulse frequency was 500Hz, the duty ratio was 0.5, the average current density was 300A/m2, after electrolysis for 2h under the condition, the current efficiency can reach 88.3%, being improved by 8.72% and anode slime was 0.49g, being reduced by 55.5% compare to 300A/m2 of DC electrodeposition. In addition, PC electrodeposition method may have a certain significance to the development of electrolytic manganese industry.

Evaluation of pulse electroplated cobalt/yttrium oxide composite coating on the Crofer 22 APU stainless steel interconnect

Ferritic stainless steels have been evaluated as favorable materials for utilization in SOFC interconnects. However, there are difficulties in utilizing these metallic interconnects, including the quick decrease of their electrical conductivity and cathode poisoning due to the evaporation of Cr species. In this work, Co and Co/Y2O3 composite coatings have been deposited onto Crofer 22 APU stainless steels by the pulse current electrodeposition method and the oxidation and electrical properties of uncoated and coated steels have been evaluated. Cyclic oxidation was performed in air at 800 °C for 500 h, oxidation rates were calculated, and oxide layer microstructures were examined. SEM–EDS and XRD investigations exhibited the created oxide layer on both coated samples made up of two scale after oxidation. The internal thin scale was composed of Cr and O and the external scale comprised of Co, Mn, Cr, Fe, and O. Y2O3 was observed as dispersed particles in the external oxide scale after the cyclic oxidation test. The thicknesses of internal oxide scale were reduced and oxidations rates also were meaningfully decreased for Co/Y2O3-coated steels relative to uncoated and Co-coated steels. Finally the ASR values of coated and uncoated substrates was also tested as a function of temperature and time in air. Results showed that the ASR value of the Co/Y2O3-coated steel was 13.1 mΩ cm2 after 500 h of cyclic oxidation at 800 °C, which was significantly lower than that of bare steel and the Co-coated sample.

Improved high-rate performance of a supercapacitor electrode from manganese-oxide-coated vertically aligned carbon nanotubes prepared by a pulsed current electrodeposition method

Although manganese oxide (MnO2) can be incorporated with vertically aligned carbon nanotubes (VACNTs) to improve supercapacitor performance potentially, one of the hurdles that hampers this embodiment is a difficulty of coating MnO2 on VACNTs homogeneously. As a way of overcoming this hurdle, we present here a facile method of pulsed current electrodeposition that turns out to exceed conventional methods in coating quality. Such improvement leads to a clear enhancement in gravimetric specific capacitance, reaching a state-of-the-art value of 243.3 F/g at a high scanning rate of 100 mV/s. In the course of this characterization, diffusion hindrance through a MnO2 layer clogging over VACNTs is found out to limit the device performance at high mass loading. An empirical relationship is proposed to explain such phenomenon and demonstrates good application in various conditions. The optimized VACNTs/MnO2 electrode also reveals outstanding high-rate performances.

Studies on the Optical and Electrical Properties of Transparent, Conductive Gallium-Doped Zinc Oxide with Ag Nanoparticles

Ag nanoparticles were deposited on top of a gallium-doped zinc oxide (GZO) layer utilizing a pulsed current electrodeposition method. Scanning electron microscopy images confirmed that the formation of Ag nanoparticles spanning several tens of nanometers in diameter occurred, which were able to reduce the sheet resistance of GZO film by approximately 28% compared with the bare GZO film. The reduced sheet resistance of the GZO film was mainly attributed to the increase in the electron concentration on the GZO surface. Absorption and photoluminescence (PL) data showed that both the increased absorption and the PL intensity of the GZO films with Ag nanoparticles were due to the surface plasmon resonance phenomenon of the Ag nanoparticles' conduction electrons.

Modified crystal quality of Cu(In,Ga)Se2 solar cells: Elimination of island-shaped indium layer by pulse current electrodeposition method

The island-shaped surface morphology of electrodeposited In film is one of the major obstacles to improve the efficiency of Cu(In,Ga)Se2 (CIGSe) solar cells, which detrimentally affects the composition and thickness uniformity of the stacking Cu/In/Ga precursors and absorbed layers. In this study, pulse current electrodeposition method was used to deposit smooth and uniform In film on Mo/Cu substrate. Flat In film with smooth surface and compact structure was deposited with pulse current density j ≥ 62.5 mA cm−2, pulse frequency f ≥ 1000 Hz, and duty cycle γ = 25%. CIGSe absorber films with flat surface and large grains were prepared by selenizing the stacking metal layers deposited by pulse current method. Finally, the CIGSe solar cell with conversion efficiency of 10.78% was fabricated based on the smooth In films, which was better than that with island-shaped non-uniform In films.

Pulse Plating of Copper onto Gas Diffusion Layers for the Electroreduction of Carbon Dioxide

ABSTRACTThis paper discusses a pulse electroplating method for preparing copper (Cu)-coated gas diffusion electrodes (GDEs) for the electrochemical conversion of carbon dioxide (CO2) to hydrocarbons such as ethylene. Ionomer coating and air-plasma surface pre-treatments were explored as means of hydrophilizing the carbon surface to enable adhesion of electrodeposited material. The pulsed-current electrodeposition method used successfully generated copper and copper oxide micro- and nano-particles on the prepared surfaces. Copper(I) species identified on the ionomer-treated GDEs are presumed to be highly active for the selective generation of ethylene as compared to other gaseous byproducts of CO2 reduction. Conversely, copper catalysts deposited onto plasma-treated GDEs were found to have poor activity for hydrocarbon production, likely due to substantial metallic character. Of note, plasma treatment of an ionomer-treated GDE after copper plating yielded further improvements in catalytic activity and durability towards ethylene production.

Repair of concrete crack by pulse electro-deposition technique

Electro-deposition is a new technique that has been developed recently to rehabilitate cracked reinforced concrete. While pulse current has been proven to be superior to direct current in the electro-deposition method, there is lack of research on applying pulse current electro-deposition method in repair of concrete cracks. Using electro-deposition method with two different types of current, this study investigated the healing effect of reinforced concrete cracks, and the behavior was compared between pulse current and direct current. The results indicate that using pulse current brings a better healing effect in terms of higher ratios of weight gain, surface coating, crack closure and crack filling depth. In addition, X-ray diffraction and scanning electron microscopy were used to assess the effectiveness of the electro-deposition method, and it is found that the pulse current has no impact on the composition of the sediments, but changes the morphology.

Corrosion resistance and micro-tribological properties of nickel hydroxide-graphene oxide composite coating

The nickel hydroxide-graphene oxide (Ni(OH)2-GO) composite coating was facilely formed on the 316 stainless steel (SS) by a pulse current electrodeposition method. The aggregation of Ni(OH)2 particles and GO in the deposition process resulted in the formation of a compact composite coating on the SS substrate. The compact composite coating provided an excellent barrier against corrosion of the SS as the corrosion inhibition efficiency and protection efficiency reached 97.1% and 98.7%, respectively. In addition, the micro-tribological test by AFM demonstrated that the coatings greatly decreased the friction on the SS surface. The lubrication of the coatings strongly depended on their compositions.

Nano-Engineered Materials for Energy Conversion and Storage Applications: Synthesis, Characterization, and Mathematical Modeling

Pulsed current electrodeposition (PCE) was employed to deposit a number of metals on different substrates for various applications. Influence of key PCE parameters, including duty cycle, peak deposition current density, pulse on-time-on and off-time and type of pulse waveform, on the morphology, size, distribution and catalytic activity of the electrodeposited layers were investigated. Platinum and palladium were electrodeposited on carbon substrates for fuel cell applications and nickel, copper, cobalt and platinum were electrodeposited on highly ordered titania nanotubes (TNTs) for solar hydrogen generation and wastewater treatment processes. The presence of nanocrystalline platinum and palladium, ranging from 2-10 nm in diameter, on carbon paper and cloth were confirmed by scanning electron microscopy and x-ray diffractometry. Their catalytic activity also was examined by fabricating membrane-electrode assemblies and testing them in single-cell proton exchange membrane and direct methanol fuel cells. Doped TNTs also were characterized by microscopy, x-ray diffractometry and UV-Vis spectroscopy. Structural investigation of the prepared TNTs via a simple anodization technique followed by metal doping, utilizing the aforementioned PCE method, confirmed the presence of anatase nanocrystalline TNTs after annealing in air and vacuum at elevated temperatures. The presence of nickel and copper nanoparticles 10-50 nm in diameter also was observed and, subsequently, confirmed. The efficiency of the photoanodes was found to increase as the amount of dopant increased to 3%. Further increase in metal dopants, however, resulted in a decrease in efficiency. A comprehensive mathematical model based on progressive nucleation was developed to accurately predict the influence of the aforementioned electroplating parameters on the resulting layers and films with the aim of process optimization for a particular plating system. The model takes into account contributions from both nucleation and growth currents and assumes a dynamic; i.e., changing, diffusion coefficient during electrodeposition. According to this model, high peak deposition current densities, low duty cycles, pulses delivered in microsecond range and employing a ramp-down waveform yielded the highest nucleation rates, leading to the smallest average grain size of the deposited nanoparticles, and confirming the experimental findings.

Effect of Pulse Frequency on the Deposition of Cu-Fe Alloy via Pulsed Current Electrodeposition Method

In an attempt to reduce the oxidation and Cr evaporation rates of solid oxide fuel cells (SOFCs) interconnect, Cu-Fe coating was developed on the AISI 430 ferritic stainless steel substrate by a pulsed current electrodeposition method. Effects of pulse frequency on properties and performance of the fabricated coating were investigated. Results show that Cu-Fe alloy was sucessfully fabricated using pulse deposition methods. The variation of pulsed frequency during pulse current deposition strongly influence the coating morphology and its composition. The increase of pulse frequency tend to increase the Cu-Fe grain size. Moreover, the amount of Cu particles decreases with the increase of pulse frequency.