The effects of coumarin on the electrodeposition of nickel

Systematic variations in the thickness of the diffusion boundary layer over a rough surface are an essential factor in producing the levelling action of metals electrodeposited in the presence of levelling additives. Information on the behaviour of these additives at an electrode at which metal is being deposited and their effects on metal deposition under conditions of known diffusion-layer thickness is therefore valuable for understanding the mechanism of levelling. Experiments are described which show that the behaviour of additives in the electrodeposition of metals can be studied under conditions of known rates of transport of additive to the electrode using a rotating disk electrode.

In the deposition of nickel from a Watts-type solution, coumarin reduces the current efficiency for nickel deposition. The current efficiency for hydrogen evolution is increased, the coumarin encouraging evolution from a few points on the electrode.

The analysis of products has confirmed that reduction to melilotic acid is the principal cathodic reaction of coumarin but there is a small amount of a second product. Coulomb balances show that this is a product involving the addition of many more than two electrons to each coumarin molecule.

The diffusion coefficient for coumarin in the Watts nickel solution has been measured and used to calculate rates of transport of coumarin to the cathode under various conditions. These have been compared with measured rates of coumarin consumption. The comparison has shown conditions where the rate of consumption is transport controlled and where it is electrochemically controlled.

The levelling power of coumarin on a rough surface has been derived from the results. This shows maxima in levelling power as a function of coumarin concentration resulting from the change over from transport to electrochemical control of the rate of coumarin consumption.     

Zinc deposition and dissolution in methanesulfonic acid onto a carbon composite electrode as the negative electrode reactions in a hybrid redox flow battery

Electrodeposition and dissolution of zinc in methanesulfonic acid were studied as the negative electrode reactions in a hybrid redox flow battery. Cyclic voltammetry at a rotating disk electrode was used to characterize the electrochemistry and the effect of process conditions on the deposition and dissolution rate of zinc in aqueous methanesulfonic acid. At a sufficiently high current density, the deposition process became a mass transport controlled reaction. The diffusion coefficient of Zn²⁺ ions was 7.5 × 10⁻⁶ cm² s⁻¹. The performance of the zinc negative electrode in a parallel plate flow cell was also studied as a function of Zn²⁺ ion concentration, methanesulfonic acid concentration, current density, electrolyte flow rate, operating temperature and the addition of electrolytic additives, including potassium sodium tartarate, tetrabutylammonium hydroxide, and indium oxide. The current-, voltage- and energy efficiencies of the zinc-half cell reaction and the morphologies of the zinc deposits are also discussed. The energy efficiency improved from 62% in the absence of additives to 73% upon the addition of 2 × 10⁻³ mol dm⁻³ of indium oxide as a hydrogen suppressant. In aqueous methanesulfonic acid with or without additives, there was no significant dendrite formation after zinc electrodeposition for 4 h at 50 mA cm⁻².     

Effect of Organic Additives on Electrochemical Surface Precipitation and Polymorphism of CaCO3

The inhibition effect of three organic additives on the precipitation and polymorphism of CaCO₃ deposited on gold surfaces was investigated using electrochemical and microscopic techniques. Additives, two polyacrylic acid (PAA) polymers with different molecular weights (Mw 2100, Mw 30,000), and 1,2,4,5‐benzenetetracarboxylic acid (BTCA), were either added to the solution before or during deposition. In the presence of 100 ppm of one of the three additives in solution, almost no scale was observed on the surface for at least 24 hours. In the presence of lower concentrations of PAA Mw 2100, only distorted calcite crystals were obtained while with PAA Mw 30,000 the polymorph was spherical vaterite. A mixture of calcite and vaterite was observed with the BTCA additive. Addition of the polymers inhibits further nucleation and growth even if added after partial deposition of CaCO₃ while BTCA has no effect once nucleation has started. The results indicate that the inhibit ion effect of the PAA polymers is due to adsorption on the electrode surface while the effect of BTCA is related to chelation of calcium ions in solution.     

Electrodeposition of palladium on the copper lead frame: Electrode reaction characteristics and the effects of primary additives

This study is mainly concerned with the electrodeposition of palladium on the copper alloy lead frame used for semiconductor assembly process. The role and effect of additives on palladium electrodeposition were studied by using various electrochemical methods. Ortho-formylbenzenesulfonic acid as a primary additive was used in palladium plating on the lead frame in this study. The electrochemical characteristics of electrode reaction were measured by the hanging mercury drop electrode for electrochemical system and the qualities of the plated surface of lead frames were also examined. The additive agent in Pd solution could have been classified as the grain refiner. It acted as the electroactive species, which increased the polarization and decreased the roughness, by adsorption on the electrode in palladium pre-plated process. The reduction of palladium ion was identified to be an irreversible reaction and the diffusion coefficient of palladium ion and the reaction rate constant were obtained from chronopotentiometry experiment.     

Inhibited zinc electrodeposition: electrode kinetics and deposit morphology

The electrode kinetics of spongy and dendritic zinc deposition were studied in the presence of three inhibitors (lead acetate, tetrabutylammonium bromide and benzalacetone). It was shown that these additives increase the cathodic overvoltage, decrease the current efficiency, eliminate multiple steady states in acid electrolytes, and modify the impedance diagrams. Such changes in electrode kinetics were interpreted in terms of weaker autocatalytic adsorption of metal cations and enhanced hydrogen adsorption. It was also shown that a pH decrease had a similar effect on these reaction rates. It was concluded from very low frequency impedance measurements that the additives give rise to an accelerated nucleation rate ensuring a faster renewal of active growth sites.     

PEDOT修饰电极的制备及对对苯二酚的测定

采用恒电位沉积法,将EDOT沉积在玻碳电极表面,对玻碳电极进行修饰,制备修饰电极。利用循环伏安法在电化学工作站上进行对苯二酚的电化学测试,探究pH、扫描速率、待测液浓度等参数来制备最佳修饰电极。     

Cyclic voltammetric study of zinc and zinc oxide electrodes in 5.3 M KOH

The behaviour of zinc and zinc oxide in 5.3 M KOH in the presence of alkaline earth oxides, SnO, Ni(OH)₂ and Co(OH)₂ was examined by cyclic voltammetry. The influence of the alkaline earth oxides was compared with additives of established effects (Bi₂O₃, LiOH, Na₂CO₃ and CdO). The alkaline earth oxide each exhibits a distinct behaviour towards zincate. Whereas, a single process of interaction with zincate was shown by CaO; two modes of reaction were obtained with SrO and BaO. Solid solution formation was noticed with BeO and MgO. The other additives forming solid solution with ZnO were CdO, SnO. The ionic sizes of Ni(OH)₂ and Co(OH)₂ allow solid solution formation with Zn(OH)₂. Both Bi₂O₃ and Na₂CO₃ enter into complexation with zincate. LiOH forms two distinct zincates, of which one is an oxo zincate leaching the `hydroxyl' functionality. Cyclic voltammetry revealed the deposition of the oxide/hydroxide additives as metal prior to the onset of zinc deposition and the potential range for this additive metal deposition is almost the same for different additives (SnO, CdO, Ni(OH)₂). The beneficial action of these additives to zinc alkaline cells is associated with a substrate effect. The implication of this electrocatalytic deposition of metals on a zinc oxide electrode is also discussed.     

On the kinetics of lead electrodeposition in fluorosilicate electrolyte Part I: Inhibiting effect of sodium lignin sulphonate

The kinetics of lead electrodeposition in Betts type electrolytes was investigated by electrode impedance measurements. In the absence of additives, the complex plane impedance plots exhibit two separate capacitive features and a, low-frequency inductive loop. The sizes and proper frequencies of the capacitive loops are influenced by the current density, the electrode rotation speed and the presence of sodium lignin sulphonate (LS), a colloidal organic additive used in practice as levelling agent. The low-frequency inductive loop, connected to the active area where lead is deposited, disappears with the LS-containing electrolyte. A reaction model is proposed in which the charge transfer reaction is coupled to the formation of adsorbed complexed species able to inhibit lead deposition before diffusing towards the bulk solution. The inhibiting effect of LS additive is discussed in terms of changes in the kinetic parameters of reactions.     

Electrochemical nucleation of mercury on platinum in the presence of organic additives

The electrochemical nucleation of mercury on a platinum electrode has been studied in the presence of some organic compounds used in the deposition of bright galvanic coatings. It is established that these organic additives do not effect the thermodynamics of the nucleation process but block the electrode surface, thus decreasing the rate of nucleus formation. It is found that the growth of the stable metal clusters is inhibited in the presence of the organic substances which leads to a marked increase of the maximal number of nuclei formed on the electrode surface.     

促传剂强化臭氧氧化对硝基酚的研究

研究了传质促进剂（促传剂）对臭氧降解水中对硝基酚的影响，筛选出了两种效果较好的促进剂。实验测定了臭氧在鼓泡反应塔中的传质系数以及添加促传剂后传质系数增大的倍数。还测定了添加促传剂后酚溶液表面张力的变化，并初步探讨了促传剂的作用机理。     

Silver nucleation on mercaptoacetic acid covered gold electrodes

Silver nucleation on the mercaptoacetic acid coated gold electrode under potentiodynamic and potentiostatic conditions was investigated using cyclic voltammetry, chronoamperometry, scanning electron microscopy, and mathematical simulations. Silver was easily adsorbed on the modified electrode surface due to the complexation and electrostatic interaction of silver with the carboxyl groups of mercaptoacetic acid. The rate constants for the electrochemical reduction and oxidation of silver on the mercaptoacetic acid coated gold electrode were evaluated. The variation of the site density of silver nucleus with the deposition potential, the dependences of the nucleation rate on the deposition potential and on the driving force (the concentration of silver) were investigated. The deposition potential affected the activity of the nucleation sites but the driving force did not. These variations were explained by the existence of a distribution of site energies (mercaptoacetic acid molecules) on the electrode surface.     

Electrochemical copolymerization of aniline and aniline-2,5-disulfonic acid

Electrochemical copolymerization of aniline and aniline-2,5-disulfonic acid (ADSA) was carried out in HCl solutions. The presence of ADSA inhibited significantly the growth of polyaniline (PAn), although the voltammetry of the copolymer was still similar to that of conventional PAn. As the ADSA concentration increased, the deposition rate of the copolymer decreased rapidly and finally no solid film was deposited on the electrode surface. When the ADSA concentration was lower than ˜ 5 mM, the depression effect of ADSA on the growth rate of the copolymer is mainly due to its stronger adsorption at the electrode surface. For higher ADSA concentrations, the inhibiting effect of ADSA was dominated by its termination effects, which led to more soluble oligomers and in turn resulted in lower deposition efficiency. Electrolysis of ADSA solution might result in a water-soluble fully sulfonated PAn.     

Zinc deposition and dissolution in sulfuric acid onto a graphite–resin composite electrode as the negative electrode reactions in acidic zinc-based redox flow batteries

Electrodeposition and dissolution of zinc in sulfuric acid were studied as the negative electrode reactions in acidic zinc-based redox flow batteries. The zinc deposition and dissolution is a quasi-reversible reaction with a zinc ion diffusion coefficient of 4.6 × 10^?6 cm² s^?1 obtained. The increase of acid concentration facilitates an improvement in the kinetics of zinc electrodeposition–dissolution process. But too high acid concentration would result in a significant decrease in charge efficiency. The performance of the zinc electrode in a three-electrode system with magnetic stirring was also studied as a function of Zn(II) ion concentration, sulfuric acid concentration, current density, and the addition of additives in 1 M H₂SO₄ medium. The optimum electrolyte composition is suggested at high zinc(II) concentration (1.25 M) and moderate sulfuric acid concentration (1.0–1.5 M) at a current density range of 20–30 mA cm^?2. Whether in acid-free solution or in sulfuric acid solution with or without additives, no dendrite formation is observed after zinc electrodeposition for 1 h at 20 mA cm^?2. The energy efficiency is improved from 77 % in the absence of additives in 1 M H₂SO₄ medium to over 80 % upon the addition of indium oxide or SLS–Sb(III) combined additive as hydrogen suppressants.     

铁镍复合助剂对煤热解过程中氮迁移规律的影响

为了减少煤炭燃烧过程中NO_x的排放,在管式炉中进行了煤与金属助剂（FeCl₃、NiCl₂）的热解实验,研究了助剂负载量、热解温度、助剂添加方式对氮迁移及N₂产率的影响并且对复合助剂作用机理进行了探讨。结果表明：随着助剂负载量的增加,氮脱除率及N₂产率呈现先增加后趋于稳定的趋势,且负载量以0.8%Fe复合1.0%Ni为最佳。在700~1000℃的热解温度范围内氮脱除率及N₂产率随热解温度的增加而增加。对煤进行溶胀处理添加复合助剂后,氮脱除率及N₂产率要优于未经处理的煤样。铁基助剂与镍基助剂在催化煤热解氮迁移过程中形成互补,铁基助剂的添加增加了镍基助剂的活性,弥补了单助剂的劣势,且复合助剂相比于单助剂有更强的氮脱除效果并且N₂产率达到最高39%。铁镍复合助剂对煤中N-5转化为N₂的催化效果更加明显,因为复合助剂对吡咯的内氢转移和开环有更强的催化作用。本研究能够为煤炭洁净化利用提供理论和实验依据。     

On the behaviour of copper in oxalic acid solutions

The behaviour of copper in oxalic acid solutions was studied both by cyclic voltammetry and electrochemical impedance technique. It was shown that, due to the easy complexation of copper with oxalate ions, the species present in the solution depend on the pH. During the dissolution, it was shown that the electrode was blocked by the precipitation of copper oxalate. On the other hand, a model was proposed to explain the copper deposition in concentrated oxalic acid solution. We found a rather good agreement between the experimental and calculated impedances.     

（Fe—Ni）—MoS2自润滑复合镀层的制备及性能研究

在酸性氯化物电解液中进行了ＭｏＳ２微粒与铁、镍共沉积的试验，确定了制备（Ｆｅ－Ｎｉ）－ＭｏＳ２复合镀层的最佳工艺参数。对所得到的复合镀层的摩擦磨损特性进行了研究。结果表明：铁镍合金镀层中弥散分布着６．４１ｗｔ％的ＭｏＳ２微粒后，与Ｆｅ－Ｎｉ合金镀层，４５＾＃淬火钢和球墨铸铁相比，其摩擦系数和损率显著降低，镀层的摩擦磨损性能得到改善。     

The microstructure and electrochemical properties of boron-doped nanocrystalline diamond film electrodes and their application in non-enzymatic glucose detection

Boron-doped nanocrystalline diamond (BDND) films were deposited on Si(100) by microwave plasma chemical vapor deposition using trimethyl boron as boron source. The surface morphology, microstructure, and electrochemical properties of the BDND films were investigated. Cyclic voltammograms indicated that the BDND film electrode exhibited good reversibility and repeatability of electrode reaction using [Fe(CN)₆]^3?/4? as redox couple. The non-enzymatic glucose sensor based on the as-prepared BDND film electrode without any modification was developed, and the selective detection of glucose in alkaline solution containing interference species of ascorbic acid and uric acid was demonstrated. The results showed that glucose can be directly oxidized with a wide linear range and high sensitivity, and selectively detected in the presence of uric acid and ascorbic acid in alkaline solution using the as-prepared BDND film electrode.     

Corrosion of cyanide copper deposits on zinc diecastings in acid solutions

The corrosion potential and morphology of copper films deposited from a cyanide solution on zinc diecast were studied in acid solutions similar to those employed in industry for the deposition of a second copper layer. Open circuit potential measurements and gravimetric methods were employed to determine the influence of the copper electrodeposition variables on the corrosion potential. The influence of variables such as the presence or absence of additives, the current density and the copper or cyanide concentrations were studied. The corrosion potential decreased with increasing copper film thickness. Less protection was obtained when a thin copper layer was electrodeposited from a solution without additives. Higher protection for the same thickness was obtained from a solution with high cyanide content. This result is related to the strong interaction between cyanides and the metal surface during the electrodeposition. A smooth surface structure was observed by SEM under these conditions.     

添加剂对氨基酸多晶型溶液结晶过程影响的研究进展

氨基酸的不同晶型往往表现出不同的理化性质和药用效果。因此通过调控氨基酸多晶型溶液结晶过程得到目标晶型非常重要,其中添加剂对不同晶型的影响直接且有效,是控制晶型生产常采用的手段。本文综述了不同种类添加剂对氨基酸多晶型溶液结晶过程的影响。首先,以水溶液中不能直接得到的甘氨酸γ晶型为例,阐明了酸、碱和无机盐对其成核的促进作用,从电荷补偿角度分析了该类添加剂对不同晶型生长过程的影响机理。其次,阐述了tailor-made添加剂对氨基酸晶体形态和晶型的调控作用,重点分析了不同结构的tailor-made添加剂对晶型转变的影响规律。介绍了醇-水等混合溶剂对不同氨基酸多晶型结晶过程的选择性影响。最后,在以上分析的基础上,对通过添加剂分子设计制备不同目标晶型进行了展望。     

Anodic stripping voltammetry of zinc at boron-doped diamond electrodes in ammonia buffer solution

This paper describes the deposition of zinc(II) with anodic stripping voltammetry on the boron-doped diamond electrode. We illustrate the dependency of several parameters on the magnitude of the oxidation peak and try to optimize the method. The supporting electrolyte was found to influence the oxidation peak magnitude. Compared with acetic acid, the most frequently used supporting electrolyte, ammonia buffer solution leads to a four times higher signal. We assume that the formation of zinc complexes, primarily tetraaminezinc(II), are responsible for the better response. Further factors studied and assessed include buffer pH, buffer concentration, deposition potential, deposition time and scan rate. With the improved conditions, a final detection limit of 5 ppb was accomplished.