Zn Ni Alloy Research Articles

Pt–Ni/ZnO-rod catalysts for hydrogen production by steam reforming of methanol with oxygen

Ni, Pt and a mixture of Ni and Pt supported on ZnO-rods were evaluated in autothermal steam reforming of methanol (ASRM) for hydrogen production as a function of the reaction temperature. The catalytic materials were characterized by SEM-EDS, XRD, TEM, HRTEM, TPR and BET. Analysis by SEM and TEM showed structural modifications on the surface of the ZnO rods after Ni impregnation. The reactivity of the catalytic materials in the range of 200–500 °C showed that the bimetallic sample had better catalytic activity among all the catalysts studied. This finding could be associated to PtZn and NiZn alloys present in this catalyst, which were identified by XRD and HRTEM analyses. Catalyst characterization by XRD after the catalytic testing showed that the intermetallic PtZn phase was stable during the reaction in the Pt/ZnO-rod sample. The cubic Ni0.75–Zn0.25 structure identified in the Ni/ZnO-rod sample was transformed to Zn0.1–Ni0.9–O and metallic Ni phases, respectively. On the bimetallic PtNi/ZnO-rod sample, the cubic Ni0.75–Zn0.25 structure remained, although the tetragonal NiZn structure is unstable and was destroyed during the ASRM reaction and then a new phase of Ni0.7Pt0.3 emerged. The promotion effect of Pt and/or Ni on the ZnO-rod was clearly shown.

Synergistic inhibition effect of poly(ethylene glycol) and cetyltrimethylammonium bromide on corrosion of Zn and Zn—Ni alloys for alkaline batteries

Abstract The synergistic inhibition effect of poly(ethylene glycol)-400 (PEG-400) and cetyltrimethylammonium bromide (CTMAB) on the corrosion of Zn and Zn—Ni alloys in 8 mol/L KOH solution saturated with ZnO was observed by potentiodynamic anodic/cathodic polarization (PDP), and electrochemical impedance spectroscopy (EIS) measurements. The electrochemical studies confirmed that there was a synergism between PEG-400 and CTMAB on corrosion inhibition of Zn and its alloys. Corrosion inhibition efficiency of the mixed inhibitors, 250 mg/L CTMAB + 250 mg/L PEG-400, was found to be much higher than that of the single inhibitor, 500 mg/L PEG-400 or 500 mg/L CTMAB. Scanning electron microscopic (SEM) investigations before and after the corrosion inhibition process emphasize the synergistic effect of the mixed inhibitors. Accordingly, it was found that the addition of the investigated inhibitors to the alkaline solution enhanced the discharge and capacity of the alkaline battery anodes. The obtained electrochemical data exhibited a good correlation with the computational one.

Electrochemical analysis of an electrodeposited Zn-Ni alloy films contained EDTA stable baths in 3.5 wt% NaCl solutions

The electrochemical analysis of an electrodeposited Zn-Ni alloy coating on steel substrate from a chloride bath containing ethylene-diamine-tetra-acetic acid (EDTA) was investigated in this study. Polarization tests demonstrated that the Zn-Ni alloy deposited from 0.119 M EDTA bath at 20 mA/cm2 current density exhibited lower corrosion current (Icorr) and more positive corrosion potential (Ecorr). The impedance modulus and corrosion resistance were improved with a fine and robust uniform coating. At 24 h of immersion time, the samples exhibit higher corrosion resistance leads to the formation of strong corrosion product layers. The morphological properties, crystalline phases, and topographical structures of Zn-Ni coatings were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and atomic force microscopy (AFM). The chemical composition analysis revealed that the Zn-Ni coatings deposited from EDTA baths have higher Zn content and intensity of Ni2Zn11 γ-phase, which exhibited better corrosion resistance properties.

Effect of Zn Content on Structure, Roughness and Corrosion Behavior of Zn-Ni Alloys

Abstract In this work, Zn-Ni alloys have been deposited on steel from sulfate bath, by electrodeposition method. The effect of Zn content on deposits properties was studied by cyclic voltammetry (CV), chronoaperometry (CA), linear stripping voltammetry (ALSV) and diffraction (XRD) and scanning electronic microscopy (SEM). The corrosion behavior in 3.5 wt. NaCl solution was examined using anodic polarization test and electrochemical impedance spectroscopy. X-ray diffraction of show that Zn-Ni alloys structure is composed of δ phase and γ phase, which increase with the decrease of Zn content in deposits. Results show that deposits obtained from bath less Zn2+ concentration exhibited better corrosion resistance.

Adsorption and Fenton-like removal of chelated nickel from Zn-Ni alloy electroplating wastewater using activated biochar composite derived from Taihu blue algae

A novel biochar composite impregnated with α-Fe2O3 in hierarchical porous structures (Fe(III)-ABC-20) was synthesized by means of pyrolysis combining with KOH activation using the yearly bloomed Taihu blue algae as resources. It was found that the biochar activated by KOH obtained the specific surface area of 1657.8 m2 g−1, nearly 92.6 times larger than that of the biochar without modification (17.9 m2 g−1). Meanwhile, abundant oxygen-containing functional groups such as COOH, OH, etc. are introduced onto the surface of algae biochar. Besides, Fe(III) was successfully loaded onto the porous structure of biochar from combined characterization of XRD, SEM, TEM, FTIR and XPS. Under the optimized operating conditions of pH at 6, Fe(III)-ABC-20 and H2O2 dosage of 0.5 g and 20 mM, adsorption equilibrium and Fenton-like reaction time at 20 and 60 min respectively, the biochar composite exhibited 98.87% removal rate of chelated nickel in electroplating wastewater. Moreover, the catalyst exerted better stability after four repeated experiments, as which still remained 93.26% of nickel removal. Meanwhile, electrochemical measurements revealed the presence of ligand to metal charge transfer (LMCT), indicating the promoting of Fenton-like reaction. Noticeably, degradation pathways of N,N,N′,N′-Tetrakis(2-hydroxypropyl) ethylenediamine (EDTP), one of the main complexing agents according to the component identification using mass spectrum within electroplating wastewater are proposed. EDTP might be first degraded to 2-hydroxypropanal or 2-Aminoethyl(ethyl) amine, then further degraded to acetaldehyde or ethylene, and finally oxidized to CO2 and H2O. Therefore, the biochar composite developed here could provide a novel route for the resource utilization of blue algae and heavy metal removal in electroplating wastewater containing refractory complexing agent.

Improvement of corrosion resistance of Zn-Ni alloy coatings by anodizing in selected alcoholic solutions

The subject of this investigation is the anodic treatment of galvanic Zn-Ni alloy coatings in alkaline solutions of selected alcohols and their characterization. The process was carried out galvanostatically at an anodic current density in the range 0.06–6.25 A/dm2 for 2–60 minutes. The characterization of the formed coatings was based on the morphological studies (OM), determination of the chemical and phase composition (XPS and GIXD), as well as film thickness (UV–vis spectroscopic ellipsometry) and corrosion investigations (EIS). It was found that the coatings have a mixed oxide-alkoxide passive character with the alkoxide-rich layer on the top. The anodic oxidation led to the coloration of the alloy; various colors (beige, blue, and violet) could be obtained depending on the process parameters. The colors were strongly related to the thickness of the films, which is similar to the passive layers found on valve metals (e.g. titanium). The thickest of the conversion coatings had ca. 250 nm. The EIS investigations showed the improvement of corrosion resistance of the substrate after the anodic treatment.

Catalytic performance of zinc-supported copper and nickel catalysts in the glycerol hydrogenolysis

Abstract Gas-phase catalytic conversion of glycerol to value added chemicals was investigated over zinc-supported copper and nickel catalysts. The addition of aluminum in the support was also investigated in glycerol conversion and the results indicate an increase in the acidity and adsorption capacity for both copper and nickel catalysts. HRTEM and XRD analysis revealed NiZn alloy formation in the Ni/ZnO catalyst. The XRD patterns of the prepared ZnAl mixed oxide catalysts show the presence of Gahanite phase (ZnAl2O4). In addition, H2 chemisorption and TPR results suggest a strong metal-support interactions (SMSI) effect between Ni and ZnO particles. Bare supports ZnO and ZnAl (Zn/Al = 0.5) were investigated in the glycerol conversion and they did not present activity. Copper supported on ZnO and ZnAl mixed oxide (Zn/Al = 0.5) was active towards hydroxyacetone formation. Nickel was active in the hydrogenolysis of glycerol both for C–C and C–O bonds cleavage of glycerol producing CH4. Strong metal-support interactions (SMSI) between Ni and ZnO has a remarkable suppression effect on the methanation activity during the glycerol conversion.

Electrochemical nucleation and growth of Zn-Ni alloys from chloride citrate-based electrolyte

In this work, the effects of deposition potential, [Ni2+]/[Zn2+] molar ratio, pH and bath temperature on the electrocrystallization mechanism of ZnNi alloy from an aqueous solution containing zinc chloride (ZnCl2), nickel chloride (NiCl2) and tri‑sodium citrate as complexing agent were studied. The Zn–Ni alloys were deposited from solutions with different molar ratios (0.25; 1; 2; 4), pHs (1.5; 3; 4) and bath temperatures (20; 40; 60°C). Scharifker and Hills model, used to analyze the potentiostatic current transients, revealed that in a plating bath containing low [Ni2+]/[Zn2+] molar ratios (R≤1), the nucleation mechanism was instantaneous with a typical three-dimensional (3D) growth process, regardless of the bath pH and temperature. In Ni-rich electrolytes (R≥2), the nucleation becomes more consistent with the theoretical progressive nucleation type. The nuclei number density increased with increasing the applied cathodic potential and bath pH and decreases for both of high [Ni2+]/[Zn2+] molar ratios in solution and elevated plating temperatures. The morphological, compositional and structural characterizations of the deposits were carried out using Field-Emission Scanning Electron Microscopy (FESEM), Wavelength Dispersive X-ray Fluorescence Analysis (WDXRF) and X-ray diffraction (XRD) respectively. The obtained results revealed that nickel content of the coatings was increased by increasing cathodic potential and [Ni2+]/[Zn2+] molar ratio and ranged between 5.82 and 29.3wt% (6.44–31.59at.%). ZnNi alloys coated at room temperature from an equimolar ([Ni2+]/[Zn2+]=1) bath were composed of a mixture of two major phases: the δ-phase (Ni3Zn22) with a monoclinic structure and the γ-phase (NiZn3) with an orthorhombic structure, while for deposits obtained in Ni-rich bath, the γ-NiZn3 phase was particularly prevailing. A mechanism of anomalous co-deposition of zinc with nickel is proposed and discussed.

Microbial Corrosion Resistance and Antibacterial Property of Electrodeposited Zn-Ni-Chitosan Coatings.

Microbial corrosion is a universal phenomenon in salt water media such as seawater and wastewater environments. As a kind of efficient protective metal coating for steel, the damage of the Zn–Ni alloy coating was found to be accelerated under microbial corrosive conditions. To solve this problem, chitosan, which is considered a natural product with high antibacterial efficiency, was added to Zn–Ni electrolytes as a functional ingredient of electrodeposited Zn–Ni–chitosan coatings. It was found that the addition of chitosan significantly and negatively shifted the electrodeposition potentials and influenced the Ni contents, the phase composition, and the surface morphologies. By exposing the coatings in a sulfate-reducing bacteria medium, the microbial corrosion resistance was investigated. The results showed that compared to the Zn–Ni alloy coating, Zn–Ni–chitosan coatings showed obvious inhibiting effects on sulfate-reducing bacteria (SRB) and the corrosion rates of these coatings were mitigated to some degree. Further research on the coatings immersed in an Escherichia coli-suspended phosphate buffer saline medium showed that the bacteria attachment on the coating surface was effectively reduced, which indicated enhanced antibacterial properties. As a result, the Zn–Ni–chitosan coatings showed remarkably enhanced anticorrosive and antibacterial properties.

Role of the newly synthesized brightener in modification of surface properties of Zn-Ni alloy electrodeposited on steel substrate

In the present study, a new brightener was synthesized by condensation of salicylaldehyde and cysteine hydrochloride (SC). To examine the influence of SC on the nucleation mechanism of Zn-Ni alloy, electrodeposition, cyclic voltammetric and chronoamperometric studies were carried out. The model of Schariffker and Hills was used to analyze current transients which explained the electrocrystallization process of Zn-Ni alloy. It is revealed that Zn-Ni electrocrystallization process in presence of SC is regulated by instantaneous nucleation mechanism. The corrosion studies were done for the bright and dull zinc-nickel alloy coatings in 3.5 wt.% NaCl solution, using potentiodynamic polarization and electro­chemical impedance spectroscopic techniques. The phase structure, surface morphology and brightness of the deposit were characterized by means of X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and reflectance studies. These studies revealed the role of SC in producing a bright Zn-Ni alloy coating on mild steel substrate and also showed its improved corrosion resistant nature.

KINETICS OF ELECTRODEPOSITION OF ZINC-NICKEL ALLOY FROM SULFATE-GLYCINATE ELECTROLYTE

Kinetics of electrodeposition of a zinc-nickel alloy from the acid sulfate-glycinate electrolyte and the properties of the formed coating have been studied depending on the composition of the electrolyte and the deposition mode. Chronoamperometric studies of the electrodeposition of the zinc-nickel alloy made it possible to establish that at polarization potentials of -1.00 -1.05 V relative to the CSE, processes on the electrode proceed with diffusion control. Changing the potentials to the region of more negative values leads to kinetic difficulties. The formation of the zinc-nickel alloy from the sulphate-glycinate electrolyte is affected by the concentration of the nickel salt. The process polarization, crystallization overvoltage, the amount of nickel in the alloy depends on its content in the solution. The maximum crystallization overvoltage corresponds to the NiSO4 content in the electrolyte in the amount of 0.12-0.14 mol/l. Large partial densities of the electroreduction current of nickel during the formation of the Zn-Ni alloy correspond to the same range of concentrations. It was found that with the content of nickel sulphate more than 0.16 mol / l, the amount of nickel in the precipitate decreases. During electrodeposition of the alloy, the pH of the near-electrode layer increases as a result of hydrogen evolution. It is assumed that with the cathode current density of more than 10 mA/cm2, the formation of the zinc-nickel alloy occurs with the participation of neutral and electronegative complexes. Determination of the protective ability of samples in a 3 % NaCl solution using both chronovoltamperometry and impedance spectroscopy showed that samples with a nickel content of 14.4 % obtained in the solution with a nickel sulfate concentration of 0.12-0.14 mol/l are characterized by maximum corrosion resistance.

ZnO-promoted surface diffusion on NiO-Ce0.8Sm0.2O1.9 anode for solid oxide fuel cell

Ni1-xZnxO-Ce0.8Sm0.2O1.9 is studied as an anode material for solid oxide fuel cells with hydrogen and methanol as fuels. After reduction, Zn is incorporated into the lattice of Ni when x is less than 0.5, while NiZn alloy accompanied with ZnO is formed when x reaches 0.8. The electrochemical oxidation process of H2 on the anode is investigated with a symmetric cell under various H2 partial pressures. The addition of Zn increases the electron cloud density of Ni and thus weakens the adsorbing strength of H on Ni, accelerating the surface diffusion of H species, which is the rate determining step when the content of Zn is lower than 0.5. ZnO in the reduced Ni0·2Zn0·8O- Ce0.8Sm0.2O1.9 anode facilitates H spillover, resulting in the variation of the rate determining step and the highest activity of the anode. The cell with Ni0·2Zn0·8O- Ce0.8Sm0.2O1.9 anode shows the highest performance with both H2 and methanol fuels at 700 °C. ZnO also improves coking resistance of NiO-Ce0.8Sm0.2O1.9 anode.

Electrodeposition of composition controllable Zn[sbnd]Ni coating from water modified deep eutectic solvent

Because of the anomalous co-deposition, the preparation of Ni content controllable ZnNi sacrificial coatings with excellent corrosion resistance from aqueous solutions is a great challenge. In this paper, a novel method was developed to deposit Ni content controllable ZnNi coating by adding appropriate water (0–7 wt%) to the deep eutectic solvent. It was found that the electrochemical windows of ChCl-2urea deep eutectic solvent were nearly unchanged when the water content was <5 wt%. The Ni content in ZnNi alloy can ranged from ~96 wt% to ~4 wt% by regulating the water content and deposition potential. The Zn alloy coating with ~14 wt% Ni and single γ phase exhibited the best protective effects to carbon steel, which was deposited from reline-5 wt% water at −1.2 V. Deep eutectic solvent-water system provides a promising way of preparing ZnNi alloy coatings with controlled composition and excellent corrosion resistance.

Catalytic deoxygenation of methyl laurate as a model compound to hydrocarbons on hybrid catalysts composed of Ni–Zn alloy and HY zeolite

AbstractBACKGROUNDThe deoxygenation of renewable vegetable oils in a hydrogen atmosphere is feasible for yielding diesel‐like hydrocarbons. In this work, hybrid catalysts composed of Ni–Zn alloy and HY zeolite were designed to achieve a highly efficient deoxygenation.RESULTSNiZn‐LDH‐HY, NiZn‐O‐HY and NiZn/HY hybrid catalysts composed of Ni‐rich Ni–Zn alloy and HY zeolite were prepared by various methods. NiZn/HY prepared by a deposition–precipitation method gave higher Ni dispersion than NiZn‐LDH‐HY and NiZn‐O‐HY obtained by mortar milling. In the deoxygenation of methyl laurate as a model compound at 330 °C and 3.0 MPa, the hybrid catalysts led to higher reaction rates (ca 9.0 × 10−5 mol g−1Ni s−1) than NiZnAl not combined with HY (2.5 × 10−5 mol g−1Ni s−1). Particularly, NiZn/HY gave higher total selectivity to C11 and C12 hydrocarbons (80.2%) than NiZn‐O‐HY and NiZn‐LDH‐HY (47.4 and 41.5%, respectively).CONCLUSIONSThis work provides an approach for preparing highly efficient catalysts for deoxygenation of esters to hydrocarbons by combining Ni–Zn alloy and HY zeolite. We deem that the closer proximity between metallic Ni and acid sites facilitates the deoxygenation via a synergetic effect between the two kinds of sites. © 2019 Society of Chemical Industry

Tribocorrosion performance of Zn, Zn[sbnd]Ni with magnesium electrodeposited on medium carbon steel in a chloride environment

The damage of materials due to both wear and corrosion has a significant impact on engineering systems. Therefore, the industry has recently been more focused on the life cycle costs of the systems and has sought to improve reliability. The reliability and efficiency of machines and equipment depend on tribocomponents operating in a chloride environment. Crucial components are subjected to a wide range of devastating tribocorrosion effects, and in many operations combined with mechanical loadings.A number of protection systems to mitigate corrosion in the marine environment have been employed to counter these problems. One of them are electrodeposited coatings such as Zn and ZnNi which were documented in numerous research. Much of it has been conducted in areas of corrosion behavior, mechanical properties, and tribology. In order to enhance the corrosion resistance of zinc film, various metals have been implemented. One of them is magnesium. The influence of Mg content in the alloy on the corrosion resistance has been noted by many researchers. However, one cannot find recent scientific publications and papers presenting tribocorrosion performance of Zn-Ni-Mg alloy coatings. Therefore, tribocorrosion behavior of ZnNi alloy coating with magnesium was investigated.The main aim of this study is to investigate tribocorrosion performance of Zn, and Zn-Ni-Mg alloys coatings with a possibility to replace Zn coating in engineering systems. All coatings were provided on AISI 1045 medium carbon steel with trivalent chrome passivation. The study was carried out in a ball-on-plate combination in 3.5% solution of NaCl. A triple electrode system with a precision four-channel ATLAS 9833 potentiostat was used for monitoring the electrochemical phenomena. The reference electrode was a calomel electrode, SCE. Polarization curves for all samples in 3.5% NaCl were utilized. The evaluation of the surface wear of all samples with coatings was done. The measure of the wear was the depth of the wear trace which was defined on the basis of profilometric measurements. The value of hardness of coatings was identified.

In situ grown nanosheet Ni[sbnd]Zn alloy on Ni foam for high performance hydrazine electrooxidation

The electrocatalyst with cost effective and high performance towards hydrazine electrooxidation is critical to promote the practical application of direct hydrazine fuel cell (DHFC). Herein, an effective approach is developed to study the NiZn alloy as promising hydrazine electrocatalyst by the combined experimental and theoretical investigations. 3D nanosheet NiZn alloy with single α-NiZn phase was successfully synthesized on Ni foam (NF) substrate through the electrodepostion of NiZn alloy and followed electrochemical leaching. The NiZn catalyst exhibits the synergetic capabilities of impressively high activity with a superior current density of 370 mA cm−2 at 0.3 V, excellent durability with a retention rate of 88.7% after 5000 s and almost 100% selectivity for the complete electrooxidation of hydrazine, which is at the top level among the reported electrocatalysts for hydrazine oxidation up to now. The reason for the excellent durability of NiZn catalyst was studied. Specially, first principles calculations were employed to shed light on the catalytic mechanism of high performance NiZn catalyst.

Green diesel production over nickel-alumina nanostructured catalysts promoted by zinc

Abstract Following the one step co-precipitation technique we have synthesized a series of Ni-Zn catalysts supported on alumina. The series involves one non-promoted sample containing 60 wt % Ni and three zinc promoted samples containing 1, 2 and 5 wt % Zn and 59, 58 and 55 wt % Ni, respectively. The specimens were characterized using nitrogen sorption isotherms, H2-TPR, NH3-TPD, XRD, SEM-EDX, TEM and XPS. The catalytic performance of the samples prepared was evaluated in the selective deoxygenation of sunflower oil using a semi-batch reactor (310 °C, 40 bar of hydrogen, hydrogen flow rate equal to 100 mL/min and reactant to catalyst ratio equal to 100 mL/g). The control of the co-precipitation procedure and the direct reduction of dried precipitate resulted to mesoporous nano-structured catalysts with high surface area (247–290 m2 g−1). The non-promoted sample was mainly comprised from NiAl2O4 particles and the promoted ones from Ni-Zn alloys and intermetallic oxo-phases (IMPs) supported on largely amorphous Al2O3 nano-grains. Zinc increased the total yield of alkanes in the diesel range (n-15, n-16, n-17, n-18) though it does not affect the mechanistic scheme of the selective deoxygenation of sunflower oil which is largely realized via decarbonylation/decarboxylation. The promoting action of zinc was attributed to the favoring of the Ni-Zn alloys and IMPs formation. It is more pronounced in the sample with the medium zinc content (58 wt % Ni, 2 wt % Zn, 40 wt % Al2O3) in which an increase of 18% in the total yield of hydrocarbons has been obtained. The maximization of the zinc promoting action in this sample reflects the good compromise between the extent of alloying and surface acidity.

Effect of Additives on Electrodeposition of Zinc-Nickel Alloy On Mild Steel

Considering the good corrosion resistance of Zn-Ni alloy, it is selected in the present study to be the protective coating on mild steel and it is considered as a strong candidate for the replacement of environmentally hazardous cadmium. Zn-Ni alloy coating is applied by electrodeposition at optimum temperature, current density and time. The bath solution used is consisting of EDTA as complexing agent. The electrodeposition is also carried out with tartaric acid and benzaldehyde additives to have good corrosion resistance and brightness. The electrodeposits obtained with and without additives are examined for nature and alloy composition. The corrosion behaviour of the electrodeposits is studied by Tafel polarization and electrochemical impedance spectroscopy.

Catalytic performance of Ni supported on ZnO‐Al2O3 composites with different Zn content in methane dry reforming

AbstractBACKGROUNDBecause of increasing environmental contaminations, hydrogen has attracted much attention as an effective and clean energy source. In addition, hydrogen and syngas are raw materials used in the production of valuable compounds. Methane dry reforming is one common method for syngas production. In this work, Ni catalysts supported on different ZnO–Al2O3 composite oxides were prepared. The effects of variation in Zn/Al ratio (Zn/Al = 0, 0.33, 0.5, 1, 2 and 3) on physico‐chemical properties and their activity and stability in methane dry reforming were investigated.RESULTSThe results indicated that Zn addition led to decreasing surface area, weakening the interaction between active phase and support, improving Ni reduction and therefore enhancing initial activity.CONCLUSIONWhen Zn content was low or just enough to produce ZnAl2O4 phase, only metallic Ni particles were detected after reaction which led to carbon filaments formation and deactivation of catalysts. Increasing Zn content formed NiZn alloy that played essential roles in activity and stability. High amounts of Zn (Zn/Al = 3) did not favor promoting effects due to the increasing active phase sizes and decreasing contact area. Ni/ZnO–Al2O3 with Zn/Al = 2 exhibited the highest activity and stability in methane dry reforming. © 2018 Society of Chemical Industry

Electrochemical studies of 2-aminopyridine on nanocrystalline Zn[sbnd]Ni alloy electrodeposition

Nanocrystalline alloy exhibit superior characteristics that are not typically found in conventional coating and its formation is usually induced by additives. However, the influence mechanism of additives on the electrodeposition process was rare to be investigated, especially in the molecular scale. In this study, nanocrystalline ZnNi alloy was electrodeposited from the bath containing 2-aminopyridine as a novel additive and the influence mechanism of 2-aminopyridine in contrast with triethylenetetramine, vanillin and coumarin on electrodeposition of nanocrystalline ZnNi alloy was studied by the combined theoretical and experimental studies. It is found that intermediate Znad+ can catalyze the reduction of Zn2+ and Ni2+. The electrodeposition mechanism of ZnNi alloy is unchanged both without and with 2-aminopyridine, however an increased overpotential is observed with 2-aminopyridine, which is related to its strong adsorption on electrode surface. Triethylenetetramine increase the ZnNi deposition overpotential by complexing with metal ions. Vanillin and coumarin is achieved mainly by their spot adsorption of oxygen atoms on electrode surface. While synergistic surface adsorption of the amine group and adsorption ring plane in 2-aminopyridine maximizes the ZnNi deposition overpotential, leading to the formation of nanocrystalline ZnNi alloy.