Journal of Electrochemistry

Table of Contents-2018,Vol 24(1)

2018, 24(1): 0.

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        Electroplating and surface finishing, which belongs in the category of electrochemical industry, is an ancient science having a long history and playing an important role in many fields of the national economy, for instance, machinery manufacturing, power electronics, instrumentation and aerospace. However, researches and developments in electroplating and surface finishing have been significantly impeded due to the resources constraints and environmental concerns. It is, therefore, urgent for the general electroplating scientists and engineers with unremitting efforts to develop new technologies and new processes to meed the new demands in order to relieve the pressures in resources and environments.
　　The disciplinary of electroplating and surface finishing covers a variety of fields including electroplating, electroless plating, anodizing, phosphating, passivation, and electrolysis. The common developing directions toward new technologies related to those areas are: (1) the preparation of surface layers with more excellent performances, namely, corrosion resistance, wear resistance, conductivity, weldability, stability; (2) the use of solutions containing less complex, lower toxic or nontoxic, and less expensive chemical compositions; (3) the application of more simplified operation process for achieving more convenient maintenance and management; (4) the decrease in production costs, and consumptions of power and heat; (5) the reduction or suppression in the production process for the emissions of waste water, waste gas and waste residue as far as possible to make an environment more friendly.
        In recent years, the researches in electroplating and surface finishing technology have been developed rapidly. From the aspects of green and environmental protections, new technologies such as trivalent chromium electroplating, cyanide free electroplating and chromium free passivation have been explored. In addition, electrodepositions of rare metals and their alloys from molten salts electrolytes and electrodepositions of special functional materials from ionic liquids electrolytes have also been studied. In terms of research methods, besides the traditional electrochemical techniques and surface analysis technologies, quantum chemical calculations and molecular dynamics simulations have been applied to optimize compositions of electrolytes and to predict the properties. Electroplating and surface finishing technologies have already broken through the traditional realm, making more and more wide applications in the manufactures of functional materials and nano materials.　　
　　Combining with the above research directions, I am glad to present in this special issue the latest publications, which are written by six distinguished professors in the fields. These publications include: two papers related to electroplating titled “Deposition Mechanism and Coating Characterization for the Trivalent Chromium Electrodeposition in Sulphate Electrolyte” and “Preparation and Characterization of Titanate-Phosphate Passivation Film on Tinplate", one paper related to metal surface modification titled “Superhydrophobic Surface on Aluminum Alloy by Hydrothermal Method and Its Electrochemical Performance”, two papers related to electroplating of nano materials titled “Preparation and Properties of Nanocrystalline Nickel by Pulse Electrodeposition on Glassy Carbon” and “Electrodeposition of CIGS Thin Film with Special Structure Using Laser Etching Template”; and one paper related to ionic liquid electroplating titled “Surface Ehancement of Nickel Ions on Cyanide Free Immersion Gold Deposited from a Chloroauric Acid-Choline Chloride Solution on Medium-Phosphorus Nickel”.
       I would like to take this opportunity to acknowledge all the participants, authors, reviewers, and editorial staffs of Journal of Electrochemistry for their excellent and professional contributions to this special issue.

Electrodeposition of CIGS Thin Film with Special Structure Using Laser Etching Template

YU Jin-zhi, LIAN Ye, ZHANG Jin-qiu, YANG Pei-xia, AN Mao-zhong

2018, 24(1): 4-12. doi:10.13208/j.electrochem.170446

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Copper indium gallium selenide (Cu_1.00In_xGa_1-xSe_2.00, CIGS) thin film solar cells have a wide application in semiconductor thin film batteries. The CIGS absorbing layer is the key of the thin film solar cell material. Therefore, it is of theoretical and practical significance to carry out researches in CIGS thin films. In this work, the CIGS thin films with special structures were prepared by using laser etching template. The copper thin film was firstly electrodeposited in aqueous solution with Laser etching template. The influences of temperature, current and concentration of copper sulfate on morphology and structure of the thin film were studied. The results showed that a hollow steamed bun shape and open bowl structure was formed at the surface of copper thin film electrodeposited at 30 ℃ and at the apparent current density of 4 A·dm^-2 in the aqueous solution with the concentrations of CuSO₄·5H₂O being 20 ~ 50 g·L^-1. The CIGS thin films were electrodeposited by using laser etching template in the ionic liquid 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([BMIm][TfO]) - 30 Vol% propyl alcohol mixed electrolyte solution at different deposition potentials, substrates and deposition time. It was demonstrated that the clusters of flowers with approximate columnar CIGS thin film could be prepared at 1.8 V for 1.5 h. Furthermore, the electrodeposition of CIGS thin films was done on the previously electrodeposited copper substrate by Laser etching template. A uniform and orderly spheroidal structure of Cu/CIGS composite film was obtained. The apparent surface area of the Cu/CIGS composite film, calculated by constant voltage square wave method, was about 8 times larger than that of the CIGS thin film prepared without using template, which greatly enhanced absorption of light on the thin film and increased the output of the carrier. Therefore, it can be expected that the CIGS thin film with globular special structure electrodeposited in ionic liquid by laser etching template may highlight the electric conversion efficiency.

Preparation and Characterization of Titanate-Phosphate Passivation Film on Tinplate

WANG Zi-yu，WANG Ming-hao，LI De-yu，LI Ning

2018, 24(1): 13-19. doi:10.13208/j.electrochem.170442

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A passivation film was prepared on tinplate surface with a composite passivating agent made of titanate and phosphate. The surface morphologies, chemical compositions and corrosion resistances of the passivation films were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), salt spray test, Tafel polarization measurement and electrochemical impedance spectroscopy (EIS). The results were compared with those films untreated and treated with titanate or phosphate passivation. It was shown that the titanate and phosphate passivation film was mainly composed of Ti₃(PO₄)₄·nH₂O and TiO₂. The finely crystallized surface could seal holes, therefore, a good passivation performance on tinplates could be achieved.

Deposition Mechanism and Coating Characterization for the Trivalent Chromium Electrodeposition in Sulphate Electrolyte

YAN Hui，HUANG Shuai-shuai，YANG Fang-zu，TIAN Zhong-qun， ZHOU Shao-min

2018, 24(1): 20-27. doi:10.13208/j.electrochem.170441

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Linear sweep voltammetry (LSV) and cyclic voltammetry (CV) were used to study the electrodeposition mechanism of trivalent chromium on a copper electrode in the novel sulphate electrolyte for thick trivalent chromium plating. The thickness, morphology, composition, microhardness, and structure, as well as the corrosion resistance in 3.5wt% NaCl solution of the trivalent chromium coatings were investigated by X-ray fluorescence gage, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), microhardness tester, X-ray diffraction (XRD) and Tafel curve measurements. The results showed that the electrodeposition of trivalent chromium involved two consecutive one electron reduction steps. The first step, Cr³⁺ + e → Cr²⁺,is controlled by the electrochemical reduction and diffusion processes, and the second step, Cr²⁺ + 2e → Cr, is an irreversible process under the diffusion control. The trivalent chromium coating exhibited nodular nanocrystalline structure and contained a small amount of iron (1.10wt%). The microhardness of the coating reached to 789.2 Hv. The corrosion potential (E_corr) and corrosion current density (j_corr) of the coating in 3.5wt% NaCl solution were determined to be -0.29 V and 9.26×10^-5 A·dm^-2, respectively.

Superhydrophobic Surface on Aluminum Alloy by Hydrothermal Method and Its Electrochemical Performance

CHEN Xiao-hang, CHEN Mo-jing, MIN Yu-lin, XU Qun-jie

2018, 24(1): 28-35. doi:10.13208/j.electrochem.170443

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Superhydrophobic film formed on a metal surface is an effective way for corrosion protection. In this paper, the superhydrophobic film was prepared on the surfaces of aluminum alloy by hydrothermally treating with a solution containing CeCl₃·7H₂O and CO(NH₂)₂ , and a self-assemble process. The electrochemical measurements and surface morphology results confirmed that the best superhydrophobicity and electrochemical performance could be achieved with the contact angle of 155.5^o after six hours of hydrothermal reaction. Furthermore, the inhibition efficiency of 99.6% was obtained in 3.5 wt% NaCl aqueous solution, indicating the excellent corrosion resistance of superhydrophobic film.

Surface Ehancement of Nickel Ions on Cyanide Free Immersion Gold Deposited from a Chloroauric Acid-Choline Chloride Solution on Medium-Phosphorus Nickel

XU Tian-yu，WANG Shi-ying，WANG Wen-chang，CHEN Zhi-dong

2018, 24(1): 36-39. doi:10.13208/j.electrochem.170445

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The nickel ions (Ni²⁺) were introduced into choline chloride (ChCl) cyanide free immersion gold solution to improve the surface quality of electrodeposition on medium-phosphorus nickel substrate. The addition of Ni²⁺ had no significant impact on the plating speed. However, the hyperactive corrosion of nickel substrate could be effectively alleviated by the addition of 500 mg·L^-1 NiCl₂·6H₂O, and the surface morphology of gold coating could be greatly improved. The choline chloride bath has great potential for industrial production due to its high Ni²⁺ carrying capacity (2000 mg·L^-1) and superior applicability to medium-phosphorus nickel substrate.

Preparation and Properties of Nanocrystalline Nickel by Pulse Electrodeposition on Glassy Carbon

ZHANG Ya-li, ZHANG Ming-xian, GUO Teng-da, ZHAO Yan-jie, YU Sheng-xue

2018, 24(1): 40-45. doi:10.13208/j.electrochem.170444

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Nanocrystalline nickel exhibits electrocatalytic activity for methanol. In this work, nanocrystalline nickel coating has been obtained by using the double pulse method on glassy carbon materials surface. The influence of pulse conditions on the grain size of nanocrystalline nicke was studied. The concentrations and compositions of the plating bath were 300 g·L^-1NiSO₄·6H₂O，45 g·L^-1NiCl₂·6H₂O，40 g·L^-1H₃BO₃，5 g·L^-1C₇H₅NO₃S，and 0.05 g·L^-1C₁₂H₂₅NaO₄S. The optimal pulse process parameters including the average pulse current density of 100 mA·cm^-2, pulse duty ratio of 30%, pulse frequency of 1000 Hz, pH of 1.5, and treatment temperature of 55 ℃ were determined. The grain size, surface morphology, structure and electrochemical properties of the prepared nanocrystalline nickel were investigated by XRD, TEM, cyclic voltammetry and electrochemical impedance spectroscop. Accordingly, the dense, smooth, and continuous uniform electrodeposition layer with the typical face-centered cubic structure was developed. The average size of the nanocrystalline nickel was about 18 nm. Cyclic voltammetric and electrochemical impedance spectroscopic results showed that the nanocrystalline nickel electrodeposited on the glassy carbon surface had good electrocatalytic activity for methanol in an alkaline environment.

Applications of Electrospinning in Lithium-Air Batteries

FU Yue, Wang Jin, YU Hai-yang, TIAN Jing-hua, YANG Rui-zhi

2018, 24(1): 46-55. doi:10.13208/j.electrochem.161121

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Lithium-air batteries have received increasing attention as the “ultimate batteries” due to their extremely high theoretical capacity and environment friendly. However, there are still many obstacles hindering the wide applications of the lithium-air batteries owing to the limitations of large charge-discharge over-potentials, poor Columbic efficiency and cycling performance. Exploring of high-efficiency, low-cost and eco-friendly catalysts is one of the vital issues for lithium-air batteries. Meanwhile, electrospinning techniques have been under substantial developments due to its simple fabrication process, high efficiency and production. This paper reviews the recent progresses in fabrications of various novel catalysts for lithium-air batteries with electrospinning techniques, which mainly focuses on the non-precious metals catalysts, carbon-based catalysts, metal oxides catalysts and their hybrid composites.

Synthesis and Electrochemical Properties of Nickel-Rich Cathode Material LiNi_0.6Co_0.2Mn_0.2O₂ with High Initial Coulombic Efficiency

GUAN Xiao-yun, HONG Chao-yu, ZHU Jian-ping, WANG Wei-li, LI Yi-xiao，YANG Yong

2018, 24(1): 56-62. doi:10.13208/j.electrochem.170317

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Nickel-rich cathode materials LiNi_0.6Co_0.2Mn_0.2O₂（NCM622）were synthesized by a co-precipitation-solid state sintering method at different temperatures. The structure, morphology and electrochemical performance of the as-prepared materials were investigated by X-ray powder diffraction (XRD) /Rietveld refinement, scanning electron microscope (SEM) and electrochemical experiments. It is found that NCM622 calcined at 800 ℃ showed the lowest degree of cation disorder (~1.97%) with a high initial Coulombic effiency of 92.2% and the capacity retention of 81.4% after 100 cycles.

Preparation and Electrocatalytic Activity of Nitrogen-Doping Tungsten Carbide Catalyst

YANG Pian-pian, HUANG Li-zhen, LI Ying-ying, SHI Mei-qin, MA Chun-an

2018, 24(1): 63-71. doi:10.13208/j.electrochem.170222

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Tungsten carbide (WC) is a promising electrocatalyst, however, its electrocatalytic activity is far inferior to Pt and Pt-group metal. In this work, nitrogen-doping tungsten carbide (WN|WC) catalysts with a nanoplate morphology were prepared via the tungsten nitride (WN) as the precursor and sodium tungstate as the tungsten source. The SEM and TEM results indicated that carbon atoms entered into the WN lattice to form the hexagonal close packed WC phase. In this way, an atomic scale heterostructure involving the closely linked interfaces between WN and WC was created . The XRD data confirmed that the cubic crystal structure of WN was still reserved after carbonization. The XPS analyses also verified the existences of W-N and W-C. In order to discuss the effect of nitrogen doping on the catalytic performance of WN|WC, Pt/WN|WC catalyst was prepared by ethylene glycol reduction with microwave-assisted heating method. The electrochemical properties of Pt/WN|WC catalyst in methanol oxidation reaction were evaluated and compared with those of pure WC and commercial Pt/C catalysts. Electrochemical tests demonstrated that the peak current density of Pt/WN|WC was three times as that of commercial Pt/C. In addition, the excellent exchange current density, rate constant and the stable Ep_f and Ep_b values suggested that the nanoplate Pt/WN|WC has a promising application as an anode material for direct methanol fuel cells.

Effects of Carboxylic Acids on Structure and Performance of 10% Vanadium Modified Li₂FeSiO₄/C Composites

WEI Xue-xia，HUANG Jia-qi，LIU Shi-yang，CHENG Xuan，ZHANG Ying

2018, 24(1): 72-80. doi:10.13208/j.electrochem.170316

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The carbon coated 10% vanadium modified lithium iron silicate (Li₂Fe_0.9V_0.1SiO₄/C) composites were prepared by sol-gel method to form precursor and followed by solid state reaction. Effects of different carboxylic acids, namely, citric acid, acetic acid and oxalic acid, on the crystal structures, surface morphologies, interfacial characteristics and electrochemical properties of the composites were systematically investigated. It was found that a mixed P2₁ and Pmn2₁ phase was formed with the major impure phase of iron (Fe) and minor impurity of lithium silicate (Li₂SiO₃). The initial discharge capacities of 144.7, 140.3 and 168.7 mAh•g^-1 were achieved at 0.1C and room temperature, while the maximum capacities of 155.9, 145.3 and 172.0 mAh•g^-1at the 7^th, 15^thand 2^nd cycles with the capacity retention values of 68.2%, 76.7% and 59.4% were obtained upon 50 cycles for the uses of citric acid, acetic acid and oxalic acid, respectively. Consisting of three carboxyl functional groups, the citric acid based composite contained higher amount of 7.8% residual carbon, the formation of impure Fe phase was promoted, and the larger charge-transfer resistance of 147 Ω was obtained, leading to lower coulombic efficiency and poorer cycle performance. On the contrast, the acetic acid based composite containedone carboxyl functional group only, resulted in the least amount of Fe and the smaller charge-transfer resistance of 73 Ω ,which showed the best cycle performance with the largest capacity retention. However, carrying two carboxyl functional groups the oxalic acid based composite led to 6.0% residual carbon and larger flower-like morphology, which slightly improved the lithium ion diffusion coefficient, achieving more than one lithium ion (1.05) per formula unit intercalation.

Intrinsic Kinetic Properties of Ternary Material for Lithium Ion Batteries Assessed by Single Particle Microelectrode

WEI Yi-min

2018, 24(1): 81-88. doi:10.13208/j.electrochem.170209

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Electrochemical performances such as capacity, rate, cycle and thermal stability of the nickel (Ni), cobalt (Co) and manganese (Mn) ternary cathode material, LiNi_xCo_yMn_zO₂ (x + y + z = 1), are significantly influenced by the proportion of Ni, Co, and Mn elements. To obtain higher specific capacity, LiNi_0.6Co_0.2Mn _0.2O₂ (NCM622) and LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) with high amounts of Ni element were employed for the lithium ion batteries. By now, many studies have been focusing on the thermal and cycling stabilities of NCM622 and NCM811. However, there is lack of reports on the intrinsic kinetic properties of these two cathode materials. In this work, single particle microelectrode has been employed to investigate the intrinsic kinetic properties of NCM622 and NCM811 without the influences of binder, conductive agent, and electrode structure. Charge-discharge test, electrochemical impedance spectroscopy (EIS), and potentiostatic intermittent titration (PITT) methods were used for the evaluation of the kinetic properties of NCM622 and NCM811. Due to the increased Ni²⁺/Ni³⁺ and decreased Mn⁴⁺ amounts, the NCM811 material presented better kinetics properties and higher columbic efficiency compared with NCM622. The discharge capacity retention of NCM811 was above 80.8% at 20C compared to 0.5C, which is much higher than that of NCM622 with 68.6%.

An Electrochemical Investigation in the Anticorrosive Properties of Silver Nanoparticles for the Acidic Corrosion of Aluminium

H. A. Fetouh, B.A. Abd-El-Nabey, Y.M. Goher, M. S. Karam

2018, 24(1): 89-100. doi:10.13208/j.electrochem.160427

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The mass loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques were used for the determinations of the corrosion rates for aluminium in 1.0 mol·L^-1 hydrochloric acid (HCl) solutions both in the absence and presence of silver nanoparticles (SNPs) at 30 ℃. The protection efficiency was evaluated to be 96.4% for 0.014 g·L^-1 of the SNPs. It has been found that the capacity of the electrical double layer at the aluminium/solution interface was decreased with increasing the concentration of the SNPs, indicating that the SNPs were adsorbed at the aluminium surface. The Langmuir adsorption isotherm and the kinetic-thermodynamic model were fitted to the experimental data. The potential of zero charge (PZC) for aluminium was determined in order to clarify the type of interaction between the metal surface and the SNPs. The experimental data obtained by scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) spectroscopy, together with the visual inspections at the surfaces of the aluminium electrodes after the electrochemical tests, all gave very good support to those obtained by the mass loss and electrochemical measurements.