Electrocatalysis of Nitrate Reduction at Copper‐Nickel Alloy Electrodes in Acidic Media

The cathodic reduction of NO in 1.0 M HClO₄ is investigated by voltammetry at pure Ni and Cu electrodes, and three Cu‐Ni alloy electrodes of varying composition, all configured as rotated disks. Voltammetric data obtained using these hydrodynamic electrodes demonstrate significantly improved activity for NO reduction at Cu‐Ni alloy electrodes as compared to the pure Ni and Cu electrodes. This observation is explained on the basis of the synergistic benefit of different surface sites for adsorption of H‐atoms, generated by cathodic discharge of H⁺ at Ni‐sites, and adsorption of NO at Cu‐sites on these binary alloy electrodes. Koutecky‐Levich plots indicate that the cathodic response for NO at a Cu₇₅Ni₂₅ electrode corresponds to an 8‐electron reduction, which is consistent with production of NH₃. In comparison, the cathodic response at Cu₅₀Ni₅₀ and Cu₂₅Ni₇₅ electrodes corresponds to a 6‐electron reduction, which is consistent with production of NH₂OH. Flow injection data obtained using Cu₅₀Ni₅₀ and Cu₂₅Ni₇₅ electrodes with 100‐μL injections exhibit detection limits for NO of ca. 0.95 μM (ca. 95 pmol) and 0.60 μM (ca. 60 pmol), respectively.     

Electrodeposition of Zn–Ni–P compositionally modulated multilayer coatings: An attempt to deposit Ni–P and Zn–Ni alloys from a single bath

The effects of bath composition and deposition variables on the electrodeposition of Zn–Ni–P alloys were studied in order to develop a single bath for deposition of Ni–P/Zn–Ni compositionally modulated multilayer coatings (CMMCs). The basis for development of the bath was a large increase in the Ni deposition rate compared to that of Zn at low deposition overpotentials combined with the impossibility of codeposition of Zn with P. EDS analysis demonstrated that the deposits obtained from the Zn–Ni–P bath at low overpotentials were practically all Ni–P, while the alloy deposited at high overpotentials was mainly Zn–Ni with around 3.2 wt% P content.     

Initial stages of Ni–P electrodeposition: growth morphology and composition of deposits

The evolution of growth morphology and composition of deposits during the initial stages of Ni–P electrodeposition is studied using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). Combined electrochemical and surface analytical measurements show that the deposition process starts at relatively low cathodic potentials by instantaneous formation and growth of hemispherical centres. The phosphorus content of deposits in the initial deposition stages is found to increase gradually with the deposition time. Additional electrochemical and XPS measurements, carried out on Ni substrates under same polarisation conditions in a Ni²⁺ ion free electrolyte solution, show the occurrence of a time dependent Ni–P surface alloy formation indicating a strong Ni–P interaction. It is suggested that the very early stages of Ni–P electrodeposition involve a primary instantaneous nucleation of Ni followed by a Ni–P alloy formation induced by the strong Ni–P interaction. AFM images show that in advanced deposition stages the coalescence of growing Ni–P centres leads to formation of larger growth mounds. The evolution of the resulting surface roughness is analysed on the basis of the so-called dynamic scaling concept. The estimated values for the roughness exponent and the growth exponent (α=1.07±0.05 and β=0.28±0.05) correspond to a model involving a smoothing of the growing surface driven by surface diffusion.     

A study on electroplating of zinc nickel alloy with HEDP plating bath

The electroplating of bright Zn-Ni alloy process using HEDP as coordinating agent, ZNP as additive agent is studied. The effect of coordinating agent, chloride content, [Zn²⁺]/[Ni²⁺], cathode current density, temperature, and supplementary coordinating agent on Ni content is investigated; composition and physical phase of alloy plating layer, brightness of plating layer, and stability of plating solution are comprehensive considered; and also, the optimum composition of plating solution for bright Zn-Ni alloy electroplating and technological condition is determined; finally, deposition mechanism is discussed. Published in Russian in Elektrokhimiya, 2006, Vol. 42, No. 1, pp. 25–30. The text was submitted by the authors in English.     

The electrodeposition and properties of Zn-Ni + Ni composite coatings

The Zn-Ni+Ni coatings were deposited under galvanostatic conditions at the current density range from 20 to 60 mA cm^?2. The influence of deposition current density on surface morphology, chemical and phase composition and corrosion resistance of obtained coatings, was investigated. Structural investigations were conducted by X-ray diffraction method. Surface morphology and surface chemical composition of the obtained coatings were determined by a scanning electron microscope. Studies of electrochemical corrosion resistance were carried out in the 5% NaCl solution, using potentiodynamic and Scanning Kelvin Probe (SKP) methods. A possibility of incorporation of nickel powder from a suspension bath to the Zn-Ni matrix, during galvanostatic deposition was demonstrated. The results of chemical composition analysis show that the Zn-Ni + Ni coatings contain approximately 15?C18% at Ni. It was found that surface morphology, surface chemical and phase composition of Zn-Ni + Ni coatings depend in small degree on deposition current density. However, the current density influences distribution of nickel powder on the surface of these coatings. The optimal values of current density on account of corrosion resistance, are found to be j = 40?C50 mA cm^?2.     

Morphology and composition of Ni–Co alloy powders electrodeposited from ammoniacal electrolyte

In this paper, the morphology and phase structure of Ni–Co powders electrodeposited from ammoniacal electrolyte are investigated as a function of alloy powder composition. Composition of the electrolyte, i.e. the ratio of Ni²⁺/Co²⁺ concentration is found to influence both, the phase structure and the morphology of Ni–Co alloy powders. It is shown that the current density practically does not influence the morphology of Ni–Co alloy powders as well as alloy powder composition. At the highest ratio of the Ni²⁺/Co²⁺ ions typical spongy particles were obtained. With the decrease of the Ni²⁺/Co²⁺ ions ratio agglomerates of the size of about 100 μm, composed of a large number of fern-like dendrites on their surface were obtained. At the lowest Ni²⁺/Co²⁺ concentration ratio, among more dendritic particles, agglomerates typical for pure Co powder deposition were detected. It is also shown that depending on the Ni²⁺/Co²⁺ ratio different types of Ni and Co codeposition could be detected: anomalous and irregular. At the Ni²⁺/Co²⁺ ions ratio higher than 1 only β-Ni phase was detected, while at concentration ratios Ni²⁺/Co²⁺<1 h.c.p. α-Co phase together with β-Ni phase was detected in the alloy powder deposit.     

The electrocatalytic behavior of electrodeposited Ni–Mo–P alloy films towards ethanol electrooxidation

Ternary Ni–Mo–P thin films have been electrodeposited from citrate‐based electrolyte onto graphite substrates for application as anode catalysts for ethanol electrooxidation. The operating deposition parameters were optimized to produce Ni–Mo–P alloy films of outstanding catalytic activity. The phase structure of the deposits was evaluated employing X‐ray diffraction technique. Morphology and chemical composition of the deposited alloy films were studied using scanning electron microscopy and energy‐dispersive X‐ray analysis, respectively. The results demonstrated that the rate of Ni–Mo–P deposition increases with increasing the ammonium molybdate concentration in the plating electrolyte up to 10 g l^?1. Also, the amount of Mo in the deposits increases with increasing the ammonium molybdate concentration up to 7.5 g l^?1, and the maximum Mo content in the film was 9.1 at.%. The catalytic activity of Ni–Mo–P/C alloy films has been evaluated towards electrooxidation of ethanol in 1.0 M NaOH solution by using cyclic voltammetry and chronoamperometry. The catalytic performance of the prepared anodes as a function of the amount of Mo was studied. The results showed an increase in the oxidation peak current density of ethanol with increasing the Mo at.% in the deposited alloy films. Additionally, Ni–Mo–P/C electrodes displayed significantly improved catalytic activity and stability towards electrooxidation of ethanol compared with that of Ni–P/C electrode. Copyright © 2013 John Wiley & Sons, Ltd.     

A Study of Nickel Electrodeposition on Paraffin‐Impregnated Graphite Electrode

The aim of the present work was to elucidate the mechanism of electrolytic deposition of Ni on paraffin‐impregnated graphite electrode (PIGE). This process is influenced by H₂ evolution, which occurs in the same potential region. On the basis of the results obtained by linear and cyclic voltammetry, elimination voltammetry with linear scan (EVLS) was used to evaluate both processes. H₂ Evolution alone was studied in sulfate supporting electrolyte, and the previously suggested mechanism for this process according to Volmer–Heyrovsky was confirmed by EVLS. It was found that both the Ni²⁺ concentration and pH affect the polarization behavior of PIGE significantly. Two separated cathodic peaks were observed at low Ni²⁺ and high H⁺ concentrations, and the separation was better at higher scan rates. EVLS confirmed the most‐probable mechanism of Ni deposition as being controlled by slow transfer of the first electron under formation of [NiOH]⁺ as an intermediate. EVLS also indicated slow reduction of H⁺ preceding the reduction of Ni²⁺. The same was confirmed by studying the anodic dissolution at different switching potentials. The results were complemented by scanning electron microscopy (SEM).     

Synthesis of Ni–Ru Alloy Nanoparticles and Their High Catalytic Activity in Dehydrogenation of Ammonia Borane

We report the synthesis and characterization of new Ni_xRu_1?x (x=0.56–0.74) alloy nanoparticles (NPs) and their catalytic activity for hydrogen release in the ammonia borane hydrolysis process. The alloy NPs were obtained by wet‐chemistry method using a rapid lithium triethylborohydride reduction of Ni²⁺ and Ru³⁺ precursors in oleylamine. The nature of each alloy sample was fully characterized by TEM, XRD, energy dispersive X‐ray spectroscopy (EDX), and X‐ray photoelectron spectroscopy (XPS). We found that the as‐prepared Ni–Ru alloy NPs exhibited exceptional catalytic activity for the ammonia borane hydrolysis reaction for hydrogen release. All Ni–Ru alloy NPs, and in particular the Ni_0.74Ru_0.26 sample, outperform the activity of similar size monometallic Ni and Ru NPs, and even of Ni@Ru core‐shell NPs. The hydrolysis activation energy for the Ni_0.74Ru_0.26 alloy catalyst was measured to be approximately 37 kJ mol^?1. This value is considerably lower than the values measured for monometallic Ni (≈70 kJ mol^?1) and Ru NPs (≈49 kJ mol^?1), and for Ni@Ru (≈44 kJ mol^?1), and is also lower than the values of most noble‐metal‐containing bimetallic NPs reported in the literature. Thus, a remarkable improvement of catalytic activity of Ru in the dehydrogenation of ammonia borane was obtained by alloying Ru with a Ni, which is a relatively cheap metal.     

Intermediate molybdenum oxides involved in binary and ternary induced electrodeposition

The first stages of Co–Ni and Co–Ni–Mo deposition in sulphate–citrate medium at pH 4.0 were analysed. In both cases, the formation of non-hydrogenated nickel on the electrode before alloy deposition was detected by linear sweep voltammetry and inductively coupled plasma mass spectrometry. Co–Ni electrodeposition was anomalous since the Co/Ni ratio in the alloy was higher than the corresponding [Co(II)]/[Ni(II)] ratio in solution. The adsorption of Co(II) over the initial nickel could explain the anomalous codeposition, which persisted with the addition of molybdate to the Co–Ni bath. However, the formation of intermediate molybdenum oxides also took place. A mechanism has been proposed to describe the sequence of steps for Co–Ni–Mo electrodeposition. Under our conditions, the alloy is formed mainly from free Co²⁺ and Ni²⁺ cations, whereas molybdate is reduced firstly to molybdenum oxide from MoO₄(H₃Cit)²⁻ and, secondly, NiCit⁻ catalyses the subsequent reduction to molybdenum metal of the intermediate [MoO₂–NiCit⁻]_ads species.     

Kinetic studies of glucose electrocatalytic oxidation on GC/Ni electrode

Nickel‐modified glassy carbon electrode (GC/Ni) prepared by galvanostatic deposition was used for the electrocatalytic oxidation of glucose in alkaline solutions where different electrochemical methods were employed. In cyclic voltammetry studies, in the presence of glucose an increase in the peak current of the oxidation of nickel hydroxide is followed by a decrease in the corresponding cathodic current. This suggests that the oxidation of glucose is being catalyzed through mediated electron transfer across the nickel hydroxide layer comprising nickel ions of various valence states. Under the chronoamperometric regime, the reaction followed a Cottrellian behavior and the diffusion coefficient of glucose was found to be 8 × 10^?6 cm² s^?1. A mechanism based on the electrochemical generation of Ni³⁺‐active sites and their subsequent consumptions by glucose has been discussed, and kinetic parameters have been derived. The heterogeneous rate constants for the oxidation of glucose at the surface of modified electrodes were determined by rotating disk electrode using the Koutecky–Levich plots, which are in agreement with the data obtained by chronoamperometry. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 712–721, 2012     

Electrodeposition and characterization of zinc–nickel–iron alloy from sulfate bath: influence of plating bath temperature

The electrodeposition of ternary zinc–nickel–iron alloy was studied in acidic sulfate bath. The comparison between Zn, Ni, and Fe deposition and Zn–Ni and Zn–Ni–Fe co-deposition revealed that the remarkable inhibition of Ni and Fe deposition takes place due to the presence of Zn²⁺ in the plating bath. The increase in corrosion resistance of ternary deposits is not only attributed to the formation of γ-Ni₂Zn₁₁ phase but also to iron co-deposition and formation of iron phase. It was also found that the bath temperature has a great effect on the surface appearance and the deposit composition. The investigation was carried out using cyclic voltammetry and galvanostatic techniques for electrodeposition, while linear polarization resistance and anodic linear sweeping voltammetry techniques were used for corrosion study. Morphology and chemical composition of the deposits were characterized by means of scanning electron microscopy and atomic absorption spectroscopy.     

In situ green synthesis of Cu‐Ni bimetallic nanoparticles supported on reduced graphene oxide as an effective and recyclable catalyst for the synthesis of N‐benzyl‐N‐aryl‐5‐amino‐1H‐tetrazoles

In the present work, for the first time we have designed a novel approach for the synthesis of N‐benzyl‐N‐aryl‐5‐amino‐1H‐tetrazoles using reduced graphene oxide (rGO) decorated with Cu‐Ni bimetallic nanoparticles (NPs). In situ synthesis of Cu/Ni/rGO nanocomposite was performed by a cost efficient, surfactant‐free and environmentally benign method using Crataegus azarolus var. aronia L. leaf extract as a stabilizing and reducing agent. Phytochemicals present in the extract can be used to reduce Cu²⁺ and Ni²⁺ ions and GO to Cu NPs, Ni NPs and rGO, respectively. Analyses by means of FT‐IR, UV–Vis, EDS, TEM, FESEM, XRD and elemental mapping confirmed the Cu/Ni/rGO formation and also FT‐IR, NMR, and mass spectroscopy as well as elemental analysis were used to characterize the tetrazoles. The Cu/Ni/rGO nanocomposite showed the superior catalytic activity for the synthesis of N‐benzyl‐N‐aryl‐5‐amino‐1H‐tetrazoles within a short reaction time and high yields. Furthermore, this protocol eliminates the need to handle HN₃.     

Optimization of CuW alloy electrodeposition towards high-tungsten content

With the help of the factorial design of experiments, optimization of the deposition of the CuW alloy was successfully done. The important deposition parameters were identified as pH, current density, and—the most important one—copper ion concentration. All of them were examined in their wide ranges. Under optimal conditions, in a citrate bath, with copper ion concentration of 1.0 mM, at current density of −100 mA cm⁻² and at pH ca. 8.3, the alloy layer had the highest tungsten content (circa 30 wt.%), satisfactory adhesion and a smooth and crackless morphology. The structure of the electrodeposited alloy can be described as an amorphous solid solution of Cu in W with built-in Cu nanocrystals.

     

Redox non-innocence of thioether crowns: spectroelectrochemistry and electronic structure of formal nickel(III) complexes of aza-thioether macrocycles

The Ni^II complexes [Ni([9]aneNS₂‐CH₃)₂]²⁺ ([9]aneNS₂‐CH₃=N‐methyl‐1‐aza‐4,7‐dithiacyclononane), [Ni(bis[9]aneNS₂‐C₂H₄)]²⁺ (bis[9]aneNS₂‐C₂H₄=1,2‐bis‐(1‐aza‐4,7‐dithiacyclononylethane) and [Ni([9]aneS₃)₂]²⁺ ([9]aneS₃=1,4,7‐trithiacyclononane) have been prepared and can be electrochemically and chemically oxidized to give the formal Ni^III products, which have been characterized by X‐ray crystallography, UV/Vis and multi‐frequency EPR spectroscopy. The single‐crystal X‐ray structure of [Ni^III([9]aneNS₂‐CH₃)₂](ClO₄)₆?(H₅O₂)₃ reveals an octahedral co‐ordination at the Ni centre, while the crystal structure of [Ni^III(bis[9]aneNS₂‐C₂H₄)](ClO₄)₆?(H₃O)₃? 3H₂O exhibits a more distorted co‐ordination. In the homoleptic analogue, [Ni^III([9]aneS₃)₂](ClO₄)₃, structurally characterized at 30 K, the Ni? S distances [2.249(6), 2.251(5) and 2.437(2) Å] are consistent with a Jahn–Teller distorted octahedral stereochemistry. [Ni([9]aneNS₂‐CH₃)₂](PF₆)₂ shows a one‐electron oxidation process in MeCN (0.2 M NBu₄PF₆, 293 K) at E_1/2=+1.10 V versus Fc⁺/Fc assigned to a formal Ni^III/Ni^II couple. [Ni(bis[9]aneNS₂‐C₂H₄)](PF₆)₂ exhibits a one‐electron oxidation process at E_1/2=+0.98 V and a reduction process at E_1/2=?1.25 V assigned to Ni^II/Ni^III and Ni^II/Ni^I couples, respectively. The multi‐frequency X‐, L‐, S‐, K‐band EPR spectra of the 3+ cations and their 86.2 % ⁶¹Ni‐enriched analogues were simulated. Treatment of the spin Hamiltonian parameters by perturbation theory reveals that the SOMO has 50.6 %, 42.8 % and 37.2 % Ni character in [Ni([9]aneNS₂‐CH₃)₂]³⁺, [Ni(bis[9]aneNS₂‐C₂H₄)]³⁺ and [Ni([9]aneS₃)₂]³⁺, respectively, consistent with DFT calculations, and reflecting delocalisation of charge onto the S‐thioether centres. EPR spectra for [⁶¹Ni([9]aneS₃)₂]³⁺ are consistent with a dynamic Jahn–Teller distortion in this compound.     

Synthesis and characterization of graphene oxide‐based hybrid ligand and its metal complexes: Highly efficient sensor and catalytic properties

A new graphene oxide‐based hybrid material (HL) and its Co(II), Cu(II) and Ni(II) metal complexes were prepared. Firstly, graphene oxide and (3‐aminopropyl)trimethoxysilane were reacted to give graphene oxide–3‐(aminopropyl)trimethoxysilane (GO‐APTMS) hybrid material. After that, hybrid material HL was synthesized from the reaction of GO‐APTMS and 2,6‐diformyl‐4‐methylphenol. Finally, Co(II), Cu(II) and Ni(II) complexes of HL were obtained. All the materials were characterized using various techniques. The chemosensor properties of HL were investigated against Na⁺, K⁺, Cd²⁺, Co²⁺, Cu²⁺, Hg²⁺, Ni²⁺, Zn²⁺, Al³⁺, Cr³⁺, Fe³⁺ and Mn³⁺ ions and it was found that HL has selective chemosensing to Fe³⁺ ion. All the graphene oxide‐supported complexes were used as heterogeneous catalysts in the oxidation of 2‐methylnaphthalene (2MN) to 2‐methyl‐1,4‐naphthoquinone (vitamin K₃, menadione) in the presence of hydrogen peroxide, acetic acid and sulfuric acid. The Cu(II) complex showed good catalytic properties compared to the literature. The selectivity of 2MN to vitamin K₃ was 60.23% with 99.75% conversion using the Cu(II) complex.     

Effect of 3-S isothiuronium propyl sulfonate on electroless nickel deposition

The effects of organic additive, 3-S isothiuronium propyl sulfonate (UPS) on bath stability, deposition rate, reaction activation energy, and Ni-P coating composition in acidic electroless nickel (EN) plating were investigated. The study was performed by measuring the polarization curves and X-ray fluorescence spectrometer (XRF) in combination with X-ray photoelectron spectroscopy (XPS) analysis. The results show that UPS improves bath stability and increases the reaction activation energy. At lower concentration, UPS is an effective accelerator for EN deposition; whereas, at higher concentration, it decreases deposition rate. It also reveals that UPS inhibits the anodic oxidation of hypophosphite and accelerates the cathodic reduction. In addition, UPS decreases the phosphorus content in Ni-P deposit and can be adsorbed on the deposit surface and compound with Ni²⁺. On the basis of these results, the effect mechanism of UPS on electroless nickel deposition was deduced.     

Fe-Ni-S软磁薄膜的电沉积

酸性镀液中以硼酸为缓冲剂、柠檬酸三钠为配合剂,在紫铜箔上电沉积得到非晶Fe-Ni-S合金薄膜。 采用扫描电子显微镜和能谱分析技术(EDS)研究了镀液组成和沉积条件对镀层表面形貌和组成的影响。 结果表明,在镀液中加入2 g/L C7H5O3NS（糖精）和0.4 g/L 1,4-丁炔二醇可获得表面平整无裂缝和较小内应力的合金镀层;电流密度和镀液pH值对镀层组成影响较小,但施镀温度对镀层组成影响较大。 获得了理想的镀液组成和沉积条件,所得Fe73Ni9.5S17.5薄膜的X射线衍射表明其为非晶结构,在室温下具有较高的饱和磁化强度(Ms约为876.25 kA/m)和较低的矫顽力(Hc约为4.96 kA/m),具有良好的软磁性能。 循环伏安曲线和阴极极化曲线均表明,镀液中CS(NH2)2会促进Fe-Ni-S共沉积。     

ALSV investigation of the phase composition of electrolytic Cu + Sn alloys

Anodic linear sweep voltammograms (ALSVs) have been recorded for thin layers of Cu + Sn alloys electrochemically deposited on graphite from a pyrophosphate bath. Three characteristic peaks were found. The first peak, appearing in the ALSVs of all samples, could be ascribed both to pure Cu (in the deposit obtained at low cathodic polarization) and to the η-Cu₆Sn₅ phase, while one of the other two peaks appearing only in the samples obtained at low cathodic polarization should reflect the presence of the -Cu₃Sn phase. The other peak, appearing only in the samples obtained at high cathodic polarization, is likely to reflect the presence of the tin-rich β-solid solution. The phase composition, in terms of the content of different phases, was determined as a function of the thickness of the alloy as well as of the deposition potential.     

Preparation of Amorphous Film on Ni-S Alloy by Electroplating Method

IntroductionRecently,amorphousalloyshaveattTactedconsiderableattentionasnewfunctionalmaterial.Theycanbeattainedbyelectroplating,suchasplatingNi-P,Ni-B,Fe-W,Ni-Mo,Fe-P,etc..ThestructureofcodepositednickelandsulfurwasfirststudiedbyBrilllwithXRD.He,however,didnotdiscussthemethodofcodepositingnickelandsulfur.Afterwards,thereweresomereportsonNi-Sdeposit.Ingeneral,aNi-SdepositcanbeobtainedbyelectroplatingfromaWattsbathcontainingsuchsulfursourcesasthiocyanateKCNS',thioureaNH,CSNH,',andso…