Current Electrodeposition Method Research Articles

Symmetrically Controlled Design of Twin Alumina-Co Composite Thin Films

Self-assembled dual-working electrode electrolytic cells were designed to produce twin alumina-Co composite films with highly symmetrical microstructures using a deflected electric field-assisted alternating current electrodeposition method. The results show that the deposition current density, microstructure, and optical and magnetic properties of the twin composite films exhibit a high degree of symmetry. The distribution of magnetic Co particles in the alumina nanopores can be changed by adjusting the magnitude of the deflected electric field, resulting in a synchronous symmetrical change in the microstructure of the composite films, which enables the fine-tuning of the magneto-optical properties of the twin alumina-Co composite films at the microscopic scale. The current density distribution on the surface of the twin composite films along the direction of the deflected electric field was quantitatively analyzed by theoretical calculations and numerical simulations. The results show that the deposition current density gradually increases from 0.024 A/m2 in region C to 0.056 A/m2 in region A at 6 V deflection voltage. The saturation magnetization intensity gradually increases along the radial direction, which is 118, 130, and 150 kA/m, respectively

Design of alumina composite films with gradual structural color and magnetism using non-uniform electric field

Co@ alumina composite film with multicolor structural color was prepared following an alternating current electrodeposition method under a non-uniform electric field. After the electric field was established by adjusting the angle between electrodes, metal Co was deposited into the nanopores of alumina film. The results of theoretical calculations and numerical simulations show that the deposition current density on the surface of the composite film presents an arc distribution under the non-uniform deposition electric field. In addition, the microstructure of the film exhibited a gradient change along the radial direction, showing gradual structural color and magnetism. The experimental results further suggest that under a non-uniform electric field, the ability to fine-tune the microstructure and physical properties of the alumina composite film can be achieved by adjusting the angle between electrodes, thickness of the porous alumina layer, and deposition time.

Study on Nucleation and Growth Mechanism of Electrodeposited Pt-Ni Alloy

Pt-M (M=Ni, Co, Fe, et.al) alloy nanoparticle catalysts have been proved to be effective oxygen reduction reaction (ORR) catalysts with reduced Pt loading in proton exchange membrane fuel cells (PEMFCs). Electrodeposition methods have shown potential application on large-scale preparation of Pt catalysts by simplifying the synthetic settings as well as high controllability1,2. While their performance is unsatisfied due to the over-large particles and the difficulty of Pt-M co-deposition in aqueous solution. We herein modified the current electrodeposition method by switching aqueous electrolyte to water-soluble N, N-Dimethylformamide (DMF) for electrochemically co-depositing Pt-Ni alloy nanoparticles. Highly monodispersed Pt-Ni alloy nanoparticles are directly deposited on carbon substrate (Pt-Ni/C) via a facile potentiostatic technique from the selected DMF solution system and show promising specific activity towards ORR. Physiochemical characterizations, electrochemical tests and computational evaluations via density functional theory (DFT) were applied to uncover the internals of formation of highly monodispersed nanoparticles as well as the nucleation and growth of Pt-Ni nanoparticles. Our finding provides a hopeful extended Pt-M catalyst layer production strategy for PEMFCs and a new idea for the nucleation and growth mechanism for electrodeposited Pt-M alloy. Keywords: electrodeposition, Pt-Ni alloy nanoparticles, nucleation and growth mechanism, density functional theory Reference [1] A.J. Martín, A.M. Chaparro, M.A. Folgado, B. Gallardo, L. Daza, ECS Transactions, 2008, 13, 13.[2] P. Dhanasekaran, K. Lokesh, P.K. Ojha, A.K. Sahu, S.D. Bhat, D. Kalpana, Journal of Colloid and Interface Science, 2020, 572, 198. Acknowledgements This work was supported in part by National Natural Science Foundation of China (21975157) and the National Key Research and Development Program of China (2016YFB0101201 and 2016YFB0101312). Figure 1

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.

Effect of TiN concentration on microstructure and properties of Ni/W–TiN composites obtained by pulse current electrodeposition

In this study, Ni/W–TiN composites were fabricated by the pulse current electrodeposition (PCE) method. The effects of TiN concentration on the microstructure, microhardness, and wear properties of the resulting composites were investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), microhardness tester, and friction wear testing. Among the four obtained composites, Ni/W–TiN composite prepared at 8 g/L showed the densest and finest surface structure. The TiN contents in obtained Ni/W–TiN composites at 8 and 16 g/L were estimated to 8.1 and 5.4 wt%, respectively. The average Ni/W grain diameter in Ni/W–TiN composite obtained at 8 g/L TiN was recorded as 84.7 nm. The protrusion and depression heights of the composite deposited at 8 g/L were 81.8 and 45.4 nm, respectively. This composite also processed an average microhardness of 897.6 HV, with only a few shallow and narrow scratches on its worn surface, demonstrating its prominent wear resistance when compared to the other three composites.

Analysis and Growth Modeling of CuInSe2 Films by Electrodeposition for Photocell Applications

CuInSe2 (CIS) thin films were deposited onto FTO/glass substrates by continuous current potentiostatic electrodeposition method. The aqueous deposition bath was prepared from a pH = 3.0 NaBF4 supporting electrolyte, containing CuSO4, In2(SO4)3, and SeO2 precursors. The characterization of these samples was done by scanning electron microscopy, energy-dispersive X-ray spectrometry, X-ray diffractometry, Raman spectroscopy, and optical spectroscopy. The experimental techniques have allowed the understanding of the atomic concentration dynamics of samples, and its relationship with the concentration of precursors. It was obtained p-type polycrystalline semiconductor samples, with 0.95 eV gap energy; the crystalline quality of these samples was also verified. Besides this, the nucleation and growth of CIS were studied during its electrochemical deposition on top of FTO, and vitreous carbon electrodes. Chronoamperometry I-t plots permitted the study of current transients, through classic nucleation models, which were used to understand the nucleation mechanism which occurred during the electrodeposition process, besides predicting some of its characteristic properties, as its diffusion coefficient, density of active sites, and nucleation rate constant per active site. Atomic force microscopy measurements were used to investigate the first stages of growth of these CIS films, deposited at different overpotentials. Preliminary devices CIS/In2Se3/FTO were mounted, with In2Se3 (IS) film also deposited by continuous current electrodeposition. Its electrical properties were analyzed, revealing a Schottky diode like behavior; there were observed light dependent open circuit voltage generation and resistance drop, disclosing promising characteristics for photovoltaic production.

Electrochemical Synthesis of Uniform Cu2O Film and Its Photoelectrochemical Properties

Cu2O films as photocathodes were synthesized using direct current electrodeposition method. Utilizing a cyclic voltammetry (CV) test before potentiostatic electrodeposition increased the uniformity and transparency of the Cu2O film. The optical band gap of the Cu2O film obtained through electrodeposition for 7200 s was 2.1 eV, while the one electrodeposited for 1000 s showed a blue shift (2.4 eV). The high transparency of the Cu2O film electrodeposited after the CV test and increased thickness of the electrodeposited film for 7200 s did not affect the value of the photocurrent density. The photocurrent density of the electrodeposited films for time periods more than 200 s did not change considerably. The thickness of the Cu2O film electrodeposited for 200 s was measured to be 70 nm. Electrodeposition for above 200 s resulted in Cu2O films with thicknesses greater than the electron collection length, i.e. 20–100 nm, which was the reason why the photocurrent density was not improved. Electrochemical impedance spectroscopy (EIS) was used to explain charge transfer characteristics of the Cu2O photocathode. The Nyquist plot showed two semicircles, which can be attributed to the charge transfer process across the electrode/electrolyte interface and inside the electrode. The EIS data was fitted with an equivalent circuit and the parameters value was derived. Using the Mott–Schottky plot, the flat band potential and the carrier density were obtained to be 0.19 V vs. Ag/AgCl and 1.3 × 1018 cm–3, respectively.

Influence of Y2O3 nanoparticles on microstructures and properties of electrodeposited Ni–W–Y2O3 nanocrystalline coatings

In this study, Ni–W nanocrystalline alloy coatings incorporated with different amounts of Y2O3 nanoparticles (0–20 g/L in the electrolyte) were successfully synthesized via direct current electrodeposition method at an applied current density of 2 A/dm2. The microstructure, morphology, chemical composition, microhardness and electrochemical performance of the deposited coatings were comprehensively investigated to unveil the fundamental effects of the Y2O3 addition. Results indicate that Y2O3 nanoparticles were uniformly incorporated in the composite coatings. The incorporated Y2O3 nanoparticles contributed to a compact and smooth coating surface. The microstructures of the deposited coatings that determined from the broadening of X-ray diffraction peaks proved that the addition of nanoparticle resulted in microstructure refinements, and the composite coating deposited from an electrolyte containing 10 g/L Y2O3 nanoparticles showed the smallest crystallite size 15.5 nm and the largest microstrain 0.59%. The microhardness increased from 533 to 789 HV as the concentration of Y2O3 particles in the electrolyte increased from 0 to 20 g/L. Furthermore, the corrosion resistance of the composite coatings improved due to the incorporation of Y2O3 nanoparticles and the composite coating electrodeposited from an electrolyte containing 10 g/L Y2O3 nanoparticles exhibited the highest anti-corrosion performance.

Preparation of Pd/GO/Cu Electrode and Its Electrochemical Degradation for 2,4-Dichlorophenol.

Chlorinated aromatic compounds (CACs) are a class of persistent organic pollutants, which have serious damage to water environment due to their own stable structure. But a good many of CACs were abandoned because of their tremendous yields and wide applications, so it is urgent to find the effective degradation methods for CACs. The electrochemical method is supposed to be a simple, environmentally friendly and effective pathway to degrade CACs. In this paper, a Pd/GO/Cu composite electrode was prepared by a combination of impregnation method and constant current electrodeposition method, which showed good electrochemical degradation efficiency for the 2,4-dichlorophenol. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to characterize the surface structure, functional group composition, crystal structure and surface element valence of the electrode. Moreover, the stability of the electrode was investigated, and the preparation conditions of the electrode were optimized.

Effects of duty cycle and pulse frequency on microstructures and properties of electrodeposited Ni–Co–SiC nanocoatings

In this study, Ni–Co–SiC nanocoatings were fabricated using pulse current electrodeposition (PCE) method. Effects of duty cycle and pulse frequency on surface appearance, microstructure, phase structure, wear behavior, and corrosion resistance of as-deposited Ni–Co–SiC nanocoatings were evaluated by scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, nanoindentation, and both wear and corrosion tests. Results indicate that numerous small-sized grains formed on Ni–Co–SiC nanocoatings at 20% duty cycle to provide smooth, uniform, and fine microstructures. The content of SiC nanoparticles in Ni–Co–SiC nanocoatings decreased from 11.2 wt% to 7.4 wt% as duty cycle increased from 20% to 60%. However, the content of SiC nanoparticles in Ni–Co–SiC nanocoatings increased from 6.3 wt% to 9.7 wt% as pulse frequency increased from 100 Hz to 300 Hz. Ni–Co–SiC nanocoatings prepared at pulse frequency of 300 Hz and duty cycle of 20% exhibited average microhardness of 934.4 Hv and average thickness of 43.2 μm. Weight loss of Ni–Co–SiC nanocoatings at 300 Hz was only 17.2 mg, indicating significant wear resistance. In addition, Ni–Co–SiC nanocoatings produced at duty cycle of 20% and pulse frequency of 300 Hz exhibited the maximum impedance, indicating optimal corrosion resistance.

Oxidation and electrical behaviour of direct and pulse current electroplated cobalt coatings on Crofer22APU stainless steel interconnect

ABSTRACTResearches keep on to improve oxidation resistance and electrical conductivity of solid oxide fuel cell (SOFC) interconnects. In this work, Co coating was applied on Crofer22APU ferritic stainless steel interconnect by pulse current electrodeposition (PCE) method. The surface and cross-section of the samples were characterised by the SEM-EDX and XRD techniques. Investigations showed that pulse current resulted in decrease of grain size, roughness and porosity of Co deposits compared to the Co coating formed by the direct current electroplating (DCE) method. The steels were exposed to air at 800°C for 500 h and their oxidation rates were calculated. Oxidation rates were decreased for PCE-Co coated samples relative to for DCE-Co coated and uncoated samples. Electrical conductivity of the samples as a function of the temperature was also evaluated in air at 800°C. The PCE-Co coated Crofer22APU exhibited electrical conductivity as high as 54.64 S cm2 at 800°C.

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.

Excellent cyclic performance of electrolytic MnO2 in Li/MnO2 rechargeable batteries

The electrolytic MnO2 particles with α∙γ-MnO2 is successfully prepared using one-step acid constant current electrodeposition method. Scanning electron microscope, N2 adsorption/desorption method and X-ray diffraction are employed for the material characterization. Scanning electron microscope result shows that the diameter of MnO2 particle is about 350–500 nm. A lot of mesoporous exist in the as-prepared MnO2 particles, which exhibit high specific surface area and can provide significantly more electrochemical active sites for the redox reaction. The as-prepared MnO2 particles as cathode in rechargeable Li/MnO2 battery displays high discharge capacity of 202 mAh g−1 in the 1st cycle at a current density of 46 mA g−1, and its discharge capacity retention ratio can achieve 82% over 100 cycles. The discharge capacities of the 100th cycle are 152, 127 and 114 mAh g−1 at different current densities of 151, 350 and 755 mA g−1, respectively, indicating excellent rate capability. The promising electrochemical performance of α∙γ-MnO2 can make researchers focus again on using metal oxide as the cathode materials in the rechargeable Li-ion batteries.

Preparation of Pd/GO/ITO composite electrode and degradation of 2,4-chlorophene

2,4-Dichlorophenol (2,4-DCP) is a kind of toxic organic compound listed as a priority pollutant by the environmental protection agency, which will endanger the environment and human health. The accumulation of 2,4-DCP in the environment has become a serious problem today since 2,4-DCP is difficult to be degraded by traditional methods. In this study, a novel palladium/graphene oxide/indium tin oxide (Pd/GO/ITO) composite electrode was prepared by constant current electrodeposition method. And the surface morphology, crystal structure and surface element valence state of the electrode were observed and analyzed by SEM, XRD and XPS, respectively. Finally, by studying the influence of different conditions on the performance of the electrodes, the electrochemical degradation efficiency of the new electrodes on 2,4-DCP was investigated. It was found that the degradation of the Pd/GO/ITO electrodes on 2,4-DCP followed a quasi-first-order reaction under different conditions.

Mechanism and kinetic study of pulse electrodeposition process of Pt/C catalysts for fuel cells

The growth mechanism and the corresponding kinetic parameters are valuable to improve the electrodeposition method for preparing Pt-based catalysts. In this paper, the effect of the operation condition on the electrodeposition mechanism has been investigated through experiments and theoretical analysis, and the corresponding kinetic parameters were acquired. The catalytic activity of the deposited Pt catalyst prepared by the pulse current (PC) electrodeposition method was improved, compared with that of the commercial Pt catalyst and the Pt catalyst prepared by the direct current electrodeposition method. The results show that both high current density and high ton/toff in PC electrodeposition could cause large cathode overpotentials, resulting in faster nucleation rate and smaller catalyst particle size, which leads to the better reaction activity of the Pt catalyst. Finally, kinetic parameters including the constants, which relate the nucleation rate with the overpotential, the transfer coefficient and the exchange current density of the electrodeposition process, were determined.

Interface microstructure and magnetic properties of α-Sm2Co17/β-Sm2Co17 dual phase nanowire magnetic composite

The α-Sm2Co17/β-Sm2Co17 dual phase nanowire magnetic composite have been successfully electrodeposited into the highly self-ordered AAO templates using a direct current (DC) electrodeposition method and annealing process. Based on the relevant physical formula and chemical principle of atomic size and electronegativity applied in bulk amorphous alloys, the author explained the formation mechanism and amorphous characteristics of Sm–Co amorphous nanowires. It is proved that this theory coincides with the experimental results quite well. In addition, adopting the method of calculation and graph simulation, we explain the crystallization mechanism of phase transformation of Sm–Co amorphous nanowires electrodeposited in AAO template, give out a schematic illustration of the corresponding microstructures and morphologies of Sm–Co phases, and indicate the relationship between interface microstructure and magnetic properties of the α-Sm2Co17/β-Sm2Co17 dual phase nanocomposite.

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.

Characterization of Pulse and Direct Current Methods for Electrodeposition of Ni-Co Composite Coatings Reinforced with Nano and Micro ZnO Particles

Ni-Co composite coatings reinforced with ZnO particles are prepared by either pulsed current (PC) or direct current (DC) electrodeposition methods. X-ray diffraction, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and EDX mapping are employed to investigate phase structure, surface morphology, elemental composition, and elemental distribution of coating, respectively. The effects of electrodeposition parameters such as stirring rate, average current density, and ZnO particles concentration on the microhardness of electrodeposited composite coating reinforced with nano and micro ZnO particles are investigated. Optimal values are determined for all of the above-mentioned parameters, which result in the maximum hardness of the coating. Any deviation from the optimal parameters leads to a reduction of the coating’s microhardness. The SEM, atomic force microscopy (AFM), wear test, and electrochemical examinations revealed that changing the electrodeposition method from DC to PC and varying the size of ZnO particles from micro to nano affect the surface morphology from rough to smooth and reduce the surface friction coefficient, both of which enhanced the wear resistance of the coating and improved its corrosion resistance. The SEM results from worn surfaces illustrated that the size of reinforcing ZnO particles and the electroplating method change the wear mechanisms and worn surface morphology.

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.

Assessment of the Polyphenol Indices and Antioxidant Capacity for Beers and Wines Using a Tyrosinase-Based Biosensor Prepared by Sinusoidal Current Method.

The application of a novel Poly(3,4-ethylenedioxythiophene)-Tyrosinase/Sonogel-Carbon electrode (PEDOT-Tyr/SNGC) biosensor to beers and wines analysis is proposed. This biosensor implies a new Sinusoidal Current (SC) electrodeposition method to immobilize the enzyme generating a nanostructure surface. The biosensors were characterized electrochemically, employing cyclic voltammetry and electrochemical impedance spectroscopy. Sensitivity, limit of detection, and correlation coefficients of the linear fitting were 2.40 × 10−4 µA·µM−1, 4.33 µM, and R2 = 0.9987, respectively. Caffeic acid is used as the reference polyphenol. A sampling of nine beers (four lager, three stout, and two non-alcoholic beers), and four wines (three red and one white wine) purchased in a local store was performed. The Polyphenol indeces for beers and wines have been assessed using the proposed biosensor, and the obtained values are in agreement with the literature data. Antioxidant properties of the samples using the 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS) radical spectrophotometric method were also evaluated. The correlation between the polyphenol index and the antioxidant capacity was obtained for beers and wines.