Study of the Properties of Electrodeposited Polypyrrole Films

Experimental and theoretical methods have been used for characterization of the properties of polypyrrole films. The AFM studies show that the morphology of polypyrrole (PPy) films on polycrystalline gold electrodes at the first stages of synthesis depends on the structure of the metal surface. It was established that mobility of anions depends remarkably on the rate of electrodeposition of the polymer film. If PPy film was deposited at relatively low current density, mobility of ClO^- ₄ anion was not high enough to guarantee electroneutrality during redox cycling and cations take part in this process especially when Li⁺ cations were replaced by more mobile ⁺ cations. Semiempirical (AM1 and PM3) quantum-chemical methods were used for theoretical studies. It was established that different size and charge of the anions together with the variation in doping levels give rise to a different optimal conformation of oligopyrrole cations which, in turn, define the resulting polymer to be either all-anti (common linear chains) or all-syn (formation of helical structures) or a combination of the two.     

Kinetics and thermodynamics of the electrodeposition of palladium, thallium, and tellurium from different baths

Some kinetic and activation thermodynamic functions for the electrodeposition of palladium, thallium, and tellurium from the best selected baths, viz. niclosamide bath [5-chloro-N-(2-chloro-4-nitrophenyl)-2-hydroxybenzamide] for Pd, alizarin red bath for Tl, and salicylaldehyde bath for Te, are determined. Reaction rate constant (k), half-lifetime (t _1/2), activation energy (E _a), and such activation thermodynamic parameters as entropy change (ΔS*), enthalpy change (ΔH*), and Gibbs free energy (ΔG*) are calculated by applying the rate theory of the first-order reaction and the Eyring theory of the reaction rate. The effect of temperature change in the range of 30–60°C on the above parameters is studied and thoroughly discussed. The effect of metal type on both the reaction rate and the activation energy is also investigated. Published in Russian in Elektrokhimiya, 2006, Vol. 42, No. 3, pp. 264–271. The text was submitted by the authors in English.     

How a Transition‐Metal(II) Chloride Interacts with a Eutectic AlCl3‐Based Ionic Liquid: Insights into the Speciation of the Electrolyte and Electrodeposition of Magnetic Materials

Electrostatic interactions are characteristic of ionic liquids (ILs) and play a pivotal role in determining the formation of species when solutes are dissolved in them. The formation of new species/complexes has been investigated for certain ILs. However, such investigations have not yet focused on eutectic liquids, which are a promising class of ILs. These liquids (or liquid coordination complexes, LCCs) are rather new and are composed of cationic and anionic chloro complexes of metals. To date, these liquids have been employed as electrolytes to deposit metals and as solvents for catalysis. The present study deals with a liquid that is prepared by mixing a 1.2:1 mol ratio of AlCl₃ and 1‐butylpyrrolidine. An attempt has been made to understand the interactions of FeCl₂ with the organic molecule using spectroscopy. It was found that dissolved Fe(II) species interact mainly with the IL anion and such interactions can lead to changes in the cation of the electrolyte. Furthermore, the viability of depositing thick magnetic films of Fe and Fe–Al has been explored.     

A Fast Electrochemical Quartz Crystal Microbalance,which Acquires Frequency and Bandwidth on Multiple Overtones

An electrochemical quartz crystal microbalance (EQCM) is described, which measures the shifts of frequency and bandwidth on multiple harmonics with a time‐resolution of 10 milliseconds. The technique requires the process under study to be repetitive. Examples are square wave amperometry and cyclovoltammetry. Data acquisition is fast because the raw data consist of traces of the electrical admittance at fixed frequencies . A few (∼10) such time traces are acquired sequentially at a set of frequencies evenly spaced around the crystal's resonance. Since all time‐traces are triggered by the same repetitive process, plots of the conductance G (ω_i , t ) and the susceptance B (ω_i , t ) from constant time delays, t , versus frequency can be produced a posteriori. The shifts, ΔG (ω_i ) and ΔB (ω_i ) quantify a difference between two resonance curves, pertaining to the sample's reference state and the state at time t . Fitting a difference of two resonance curves to these data, one obtains shifts of frequency, Δf (t ) and shifts of bandwidth, ΔΓ(t ), versus time. This procedure is repeated for the different overtones. Given the repetitive nature of the process, one may accumulate and average, which lowers the noise down to a few tens of mHz. The capabilities of this instrument are demonstrated with two examples, which are copper deposition/dissolution and electro‐responsivity of a polymer film containing weakly acidic side groups.     

Synthesis of CuCorePtShell Nanoparticles as Model Structures for Core–Shell Electrocatalysts by Direct Platinum Electrodeposition on Copper

The synthesis of Cu(core)Pt(shell) model catalysts by the direct electrochemical deposition of Pt on Cu particles is presented. Cu particles with an average diameter of 200 nm have been deposited on glassy‐carbon electrodes by double pulse electrodeposition from a copper sulfate solution. Subsequent deposition from a platinum nitrate solution under potential control allows for a high selectivity of the Pt deposition towards Cu. Using a combination of cyclic voltammetry, XPS and sputtering, the structure of the generated particles has been analyzed and their core–shell configuration proven. It is shown that the electrocatalytic activity for the oxygen reduction is similar to that of other PtCu catalyst systems. The synthesized structures could allow for the analysis of structure–activity relations of core–shell catalysts on the way to the simple and controlled synthesis of supported Cu(core)Pt(shell) nanoparticles as oxygen reduction catalysts.     

离子液体电沉积CuInxGa1-xSe2薄膜

采用循环伏安法(CV)对离子液体Reline中三元CuCl₂+InCl₃+SeCl₄体系和四元CuCl₂+InCl₃+GaCl₃+SeCl₄体系的电化学行为进行了研究。研究表明,In³⁺并入三元CIS(Cu-In-Se)薄膜体系和Ga³⁺并入四元CIGS(Cu-In-Ga-Se)薄膜体系均有两种途径：一是发生共沉积,二是直接还原。利用电感耦合等离子体发射光谱(ICP)和扫描电镜(SEM)对沉积电势、镀液温度和主盐浓度对CIGS薄膜组成、镀层表面形貌的影响进行了测试,结果表明通过工艺参数的选择可以控制Ga/(Ga+In)和CIGS薄膜组成并得到化学计量比为Cu_1.00In_0.78Ga_0.27Se_2.13的薄膜。     

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.     

Functional silver nanostructured surfaces applied in SERS and SIMS

Present article deals with functionality of silver nanostructured surfaces prepared by potentiostatic electrochemical deposition on the paraffin impregnated graphite electrode as template‐free substrates. The effect of the electrodeposition conditions on two silver surface functions: analytical signal enhancement in Surface‐enhanced Raman spectroscopy and pre‐ionization function, applied in secondary ion mass spectrometry (SIMS) is reported. Functional silver nanostructured substrate was prepared at a potential ?850 mV with a deposition duration of 20 min. Analytical signal enhancement factors of 3.2 ×10⁵ for Raman peak at 649 cm^?1, 3.0×10⁵ for peak at 810 cm^?1 and 2.7×10⁵ for peak at 1539 cm^?1 were determined for Rhodamine 6G at deposited surface. Slight pre‐ionization effect has been observed in SIMS, and 1.2×10⁵ fold signal enhancement was established for fragment of Rhodamine 6G with m/z 429 (M‐CH₃‐Cl). Electrochemical preparation of nanostructures represents a step towards surface integration directly into miniaturized systems and sensors. Copyright © 2013 John Wiley & Sons, Ltd.     

Mechanism for nucleation and growth of electrochemical deposition of palladium(II) on a platinum electrode in hydrochloric acid solution

Palladium(II)and chloride ions tend to form complexes in aqueous solution.Both theoretical and experimental(by UV spectrum)results indicate that there are four complexes formed in aqueous solution containing 3 mol/L hydrochloric acid and 20mmol/L PdCl2.This work evaluates the kinetics of electrochemical deposition of palladium on a Platinum electrode.For this purpose,palladium electrodeposition was investigated by means of cyclic voltammetry(CV),potentiostatic current-time transients(CTTs)and Tafel curve.By CTTs curves,the regions corresponding to the charge transfer control,mixed control and diffusion control were identified.In the diffusion control region,palladium electrodeposition mechanism was characterized as progressive nucleation with three-dimensional(3D)growth under diffusion control;as for the mixed control region,an adsorption(IAds),ion transfer(IIT),and nucleation and growth(ING)model were proposed to analyze the current-time transients quantitatively,which could separate the IAds,IIT and ING perfectly.     

Process prediction of Ni–SiC coatings based on RBF-BP model

The preparation of Ni–SiC coatings using magnetic field-assisted jet electrodeposition under various plating settings is described in this study. A RBF-BP composite neural network with 4 × 4 × 4 × 7 × 10 × 1 was used to predict the corrosion resistance of Ni–SiC coatings prepared by employing different plating parameters. The results show that the fitting degree between the expected value and the actual value of the RBF-BP composite neural network is 0.97497. Moreover, the hybrid neural network can accurately predict the corrosion resistance of Ni–SiC coatings prepared under different process parameters. The corrosion weight loss of the coating is the lowest at the current density of 4 A/dm², a jet rate of 3 m/s, a SiC particle concentration of 8 g/L, and at a magnetic field intensity of 0.8 T, demonstrating its corrosion resistance under these conditions. According to the coating characterization analysis, the coating's grain size was significantly refined, and the surface was smoother with a high amount of uniformly sized SiC nanoparticles.