A two-step process was used to prepare a nickel-polyaniline nanocomposite (Ni (NPs)-PANI). The first step consisted of the electrodeposition of polyaniline (PANI) in the form of thin films on fluorine-doped tin oxide (FTO) substrates from a solution of aniline, lithium perchlorate, and sulfuric acid at a pH of 0.5. In the next step, the obtained Ni (NPs) were deposed in this polyaniline films. The structural, morphological, and electrocatalytic properties of the prepared nanocomposites were then investigated. X-ray diffraction (XRD) confirmed the cubic structure of the nanocomposites, and Fourier-transform infrared spectroscopy (FTIR) indicated the existence of nickel and polyaniline in the prepared nanocomposites. Morphological analysis carried out through SEM revealed that the nanocomposites exhibit uniform dispersion of nickel nanoparticles into the polyaniline matrix. Amperometry and cyclic voltammetry were employed to investigate the electrocatalytic glucose oxidation behavior of the nanocomposite electrode in the alkaline medium. The prepared nickel-polyaniline nanocomposite electrode exhibited high sensitivity (278.8 µA mM−1 cm−2) in a range from 0.02 to 1 mM at a sufficiently fast response time of 3 s and a low glucose detection limit of 1 µM (S/N = 3). A cost-effective and straightforward synthesis procedure to prepare Ni (NPs)-PANI nanocomposite would make this material an efficient glucose sensor with appropriate stability, higher reproducibility, and excellent sensitivity.

The electrochemical nucleation and growth of bismuth (Bi) crystallites on copper substrates were investigated using cyclic voltammetry and chronoamperometry measurements, and scanning electron microscopy (SEM). The experimental current transients were analyzed according to the Scharifker and Hills and Mirkin-Nilov and Heerman-Tarallo models. At relatively low overpotentials and low Bi concentration, Bi deposition can be described by a model involving progressive nucleation on active sites and 3D diffusion-controlled growth. At higher Bi concentration, the growth mechanism shifts to the instantaneous nucleation mode. These results were also confirmed by SEM analysis. The values of some kinetic parameters such as the nucleation rate, the number density of active sites and the diffusion coefficient of Bi3+ ions were also calculated using different theoretical approaches. X-ray diffraction measurements revealed that the Bi crystallites grow in the rhombohedral crystal structure along the [012] direction. The optical properties of the dispersed Bi nanoparticles on the Cu surface were discussed in the ultraviolet-visible (UV-Vis) wavelength range. It was found that the UV-Vis spectrum exhibit a strong resonant optical absorption on the surface with the smallest Bi crystallite size (200 nm).

To develop an efficient photocatalyst electrode for solar energy harvesting and photocatalysis application in the visible region, broadband plasmonic Cu film combined with Cu2O/TiO2 nanotube arrays heterojunction (Cu film/Cu2O/TiNT) has been successfully fabricated by anodization combined with electrodeposition method. Interestingly, linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and UV-Vis diffuse reflectance spectroscopy reveal that the combined consequence of both Cu film and Cu2O in the as-synthesized ternary composite considerably enhances light absorption in the visible spectral. This activity is attributed to the more efficient charge separation/transportation and the presence of Cu film with strong plasmon resonance (SPR) effect. Moreover, the combined effects of both Cu film and Cu2O on TiNT approved highest catalytic current density and highest photocatalytic activity on methylene blue (MB). The efficiency and the rate of MB photodegradation over the Cu film/Cu2O/TiNT were found to be triple compared to TiNT. Within only 30 min of reaction time, the photodegradation of MB reaches nearly 100%. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Herein, we report the study of the electrodeposition of copper oxides mainly Cuprite (Cu2O), paramelaconite Cu4O3 and tenorite (CuO) from a slightly acidic Cu(II) acetate solution on indium-doped tin oxide (ITO) substrate. A formation mechanism was proposed based on the observation of a series of reaction intermediates. The potential domain where the electrodeposition of copper oxides (CuxOy) is possible was investigated. The nucleation mechanism of (Cu2O) during electrodeposition was studied as a function of Cu2+ concentrations and deposition potential by exploiting the electrochemical techniques such as cyclic voltammetry and chronoamperometry. This study enabled us to demonstrate that the nucleation process and the growth of dendrites obey the model of Scharifker and Hills 3D instantaneous under diffusion control. Morphological and structural characterizations of the electrodeposit are performed by scanning electron microscopy (SEM) and X-ray diffraction (XRD).

Electrodeposition of NiFe films, on hydrogen-terminated n-Si (111)-H from acidic dilute sulphate solution, was studied by electrochemical measurements at room temperature in the presence and absence of saccharin. The electroplating process kinetics was investigated by voltammetric study and the effect of Fe2+ concentration on the deposit composition was studied as well with energy dispersive spectrometry analysis. The average composition of the Ni45Fe55 film was obtained for Fe2+ concentration in the range of [0.030–0.035] mol L−1 at a current density of −6 mA cm−2. Correlation between Fe2+ concentration in the NiFe deposit and electronic properties was examined by electrochemical impedance spectroscopy. Film roughness depends on Fe2+ concentration and a smoother deposit was obtained for the Ni45Fe55 film. Very low coercivity (less than 1.3 Oe) was measured in the Ni45Fe55 film with a nominal thickness of 640 nm. The very soft magnetic properties of the NiFe films provide information about the low level of inhomogeneities present in these films.

In the present study, electrochemical impedance spectroscopy (EIS) has been used to determine how saccharin (SAC) affects the electronic properties of the hydrogen terminated Si(111) (n-Si(111)-H)/electrolyte interface. The presence of surface states energy levels on the n-Si(111)-H surface is well demonstrated by surface states capacitance measurements. Absorption of SAC on the n-Si(111)-H is evidenced by the changes observed in surface states distribution and density. Two monoenergetic state levels situated at nearly −0.3V and 0.11V vs. SCE were found in SAC containing bath. The first surface states level have been related to the penetration of hydrogen into subsurface region, whereas the second surface states level is expected to be associated with oxidation intermediates.

Bismuth (Bi) is a semimetal, which has proved particular behavior as a plasmonic photocatalyst/cocatalyst. In the present work, we for the first time successfully synthesized Bi/alpha-Bi2O3 with a porous nanodendritic morphology on TiO2 nanotubes (TiNT) using a one-step electrodeposition process to achieve both efficient surface plasmon resonance (SPR) effect enhancement and high specific surface area. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) characterizations were employed to evaluate the physico-chemical and surface characterization of the materials. Electrochemical impedance spectroscopy (EIS) was performed to evaluate the electronic properties and charge transport of the considered materials. The photoelectrochemical characterizations of the composite were carried out through linear sweep voltammetry (LSV). LSV and UV-Vis diffuse reflectance spectroscopy demonstrate that the incorporated Bi significantly enhances light absorption in the UV and visible spectral. Significant improvement in photocurrent density, up to 5 mA cm(-2) at 1.5 V vs SCE, and a low onset potential, -0.4 V vs. SCE were found. The photoelectrochemical activity improvement can be attributed to enhanced absorption in the UV and visible light regions due to the presence of semimetallic Bi NPs with plasmon resonance (SPR) effect, more efficient charge separation/transportation due to the high specific surface area. (C) 2017 Elsevier Ltd. All rights reserved.

In this work, a simple strategy was used to prepare Ti3+ surface defect states through the simple IN irradiation of TiO2 nanotubes (TiNT) formed in ethylene glycol/NH4F/H3PO4/H2O mixture at different anodizing potentials. The band gap electronic states created by Ti3+ are mostly responsible for the effective narrowing of band gap.The effect of anodizing potential on surface states of TiO2 nanotubes/electrolyte interface has been studied under UV irradiation. A quantitative and qualitative analysis of surface states of TiNT formed at different anodizing potential was performed using capacitance measurements. These measurements allow us to provide evidence for the presence of monoenergetic surface states in the band gap. The energy levels and the density of surface states have been determined. Both density and energetic location are very dependent on the geometric characteristics. Relatively wide distribution of these states in a range of electric energy of 0.17-0.35 eV below the edge of the conduction band was obtained according to the anodizing potential. The optical absorption at 630 nm may be attributed to deep level states originated from oxygen vacancies associated with Ti3+. The presence of energetic level states and elevated surface solid fraction factor of TiNT are the determining factors in enhancing the photoactivity in visible light as evidenced by high photocurrent densities up to 16 mA cm(-2). (C) 2016 Elsevier B.V. All rights reserved.

Mn-Bi thin films were electroplated on Cu (111) substrates in an acidic chloride bath. In order to determine the deposition potential of each element, cyclic voltammetry using a rotating disk electrode was performed. Two types of thin films were obtained using two deposition mode: the first one called thin Mn-Bi layers by using a single applied potential and the second one called Mn-Bi/Bi bilayers by using a double pulse potential. Annealing treatments at 300 degrees C for 1 hour under vacuum condition were carried out in order to cause an interdiffusion between manganese and bismuth. The morphological and crystalline structure of the various deposits was investigated by scanning electron microscopy with field effect (SEM-FEG) and by X-ray diffraction analysis (XRD). Magnetic characterizations were also made using a superconducting quantum interference device (SQUID) magnetometer.The morphological and the structural properties of the thin layers and the bilayers are completely different, indicating that the growth process changes according to the plating mode. After annealing a mixed MnBiCu phase with a coercivity of 300 Oe and 400 Oe was observed on the thin layers and the bilayers respectively. (C) 2016 Published by Elsevier Ltd.

In the present work, amorphous and crystalline TiO2 nanotubes (TiNT) were fabricated via anodization and characterized as an alternative cathode for Microbial Fuel Cells (MFCs). The morphology of TiNT is characterized by scanning electron microscopy (SEM). The crystalline structure and chemical composition are examined by X-ray diffraction (XRD) and Energy dispersive X-ray spectroscopy (EDX). The electrical conductivity characteristics were examined by electrochemical impedance spectroscopy (EIS). MFCs based on the alternative cathodes were evaluated in terms of energy generation and wastewater treatment. The performances of the as-anodized nanotubes and TiNT annealed at 450 degrees C and at 550 degrees C were investigated in double-chamber MFCs with carbon rod and graphite granules as anode and polymer inclusion membrane based on ionic liquid as separator. Industrial wastewater was the source of carbon and inoculum for the experiments. The as grown amorphous nanotubes exhibited the best output power density of 15.16 mWm(-2). The results reported here indicate that the specific surface area and the oxygen vacancies of the TiNT cathode can influence the MFCs performance together, because both factors play crucial role in the oxygen reduction reaction (ORR). As-anodized TiNT, due to its higher specific surface provide more active sites for electrode reactions.The final oxygen demand (COD) for all systems achieved a COD removal within the interval 54-71% after 10 days. This approved the suitability of MFCs for wastewater treatment. (C) 2016 Elsevier B.V. All rights reserved.

We report the effect of deposition potential on the morphology, structure and magnetic properties of Ni80Fe20 (Permalloy: Py) deposits, elaborated by electrochemical process onto silicon nanowires (SiNWs). The morphology of SiNWs and Py/SiNWs were performed with scanning electron microscopy (SEM). The SEM micrographs reveal the formation of SiNWs and clearly show a change in the morphology with the deposition potential. The analysis of X-ray diffraction spectra shows a change in the texture with the deposition potential. The grain size, the lattice parameter and the strain were studied as a function of the deposition potentials. From hysteresis loops, we have shown that the magnetization easy axis is the plane of the samples.

This paper examines the corrosion behaviours of carbon steel immersed in sterile natural sea water with and without strain Bacillus cereus. Electrochemical studies, including Tafel plots and electrochemical impedance spectroscopy (EIS) were performed to evaluate the variation of the corrosion behaviour of carbon steel in medium containing B. cereus as compared to the sterile control samples. The results of Tafel plot measurements showed significant reduction in the corrosion rate in the presence of bacterial biofilm produced by strain B. cereus. The EIS data showed that the charge transfer resistance is greater in a medium containing B. cereus and increases with immersion time.

Cerium oxide (CeO2) nanoparticles (NPs) possessing defined size and crystallinity have been synthesised by a co-precipitation method. The effect of several parameters, such as the nature of the solvent and the calcination process, on the crystallite size was studied by XRD, TEM and BET methods. These CeO2 nanoparticles were then incorporated in dodecylsulfate (DS) doped PPy films during their electrodeposition in potentiodynamic conditions in order to produce PPy-DS/CeO2 NPs nanocomposite thin films on gold coated quartz crystals. Simultaneous EQCM experiments revealed successful incorporation of increasing amounts of cerium oxide nanoparticles in the polypyrrole matrix during each of the consecutive CV scans. This was confirmed using FEG-SEM and EDS microanalysis.The ion exchange phenomena occurring in the resulting nanocomposite materials were studied by ac-electrogravimetry in NaCl aqueous electrolyte. PPy-DS films appear to be mainly cation exchangers, independently from the incorporation of CeO2 nanoparticles (NPs), even though chloride anions in smaller amounts, and free water molecules, are simultaneously transferred at the film/electrolytic solution interface. This study also reveals that the kinetics of Cl- ion insertion occurring at the film/electrolyte interface upon oxidation is persistently slower in PPy-DS/CeO2 NPs films than in PPy-DS films throughout the entire potential window of investigation. However, the relative concentration changes of Cl- ions in PPy-DS/CeO2 NPs films is about two times greater than that occurring in pristine PPy-DS films. Such conclusion tends to demonstrate that CeO2 NPs have the ability to modify the morphology of electrodeposited PPy-DS thin films as well as their subsequent permeability towards ions contained in the electrolytic solution, possibly via the perturbation of polymer chain interactions and organisation. (C) 2014 Elsevier Ltd. All rights reserved.

Perpendicular Silicon nanowires (SiNWs), having 20 micrometer in length, were fabricated by metal assisted chemical etching of n-type Si(100) wafers in aqueous HF-solution. In a second step, NiFe films were electrodeposited onto theses SiNWs. The structure and magnetic properties of as deposited NiFe layers were studied by X ray diffiaction (XRD) and vibrating sample magnetometer (VSM). From X-ray diaction, the FCC NiFe structure was evidenced with a lattice constant, a, equal to 3.5270 angstrom. From hysteresis curves, we compute the coercive field, Hc, values. We found that the Hc(//) values range from 102 Oe to 236 Oe.

Three generations of TiO2 nanotubular arrays (TiNT) were obtained by anodization of titanium foil in three different solutions: Aqueous acid containing fluoride media, organic based containing fluoride media and chloride containing electrolyte.This paper investigates the effect of the electrolyte composition on barrier layer characteristics of TiNT. Correlation between the dimensional aspect of TiNT and the electrochemical properties was investigated. Electrochemical characteristic from Electrochemical Impedance Spectroscopy (EIS) were discussed. EIS is considered to be a highly sensitive technique that allows determining barrier oxide layer characteristics. Semiconducting properties as well as thicknesses are discussed in correlation with anodizing electrolyte. Scanning electrochemical microscopy (SECM) was employed for in situ characterization of surface chemical activity of titanium in chloride containing electrolyte. The SECM has detected corrosion pits as well as the surrounding cathodic reaction. Nucleated pits on titanium takes place on the top of grain most probably with surface orientation (0001). (C) 2014 Elsevier Ltd. All rights reserved.

In this paper, we report on the nucleation and the growth of heterogeneous Mn-Bi thin films on Cu substrate from a mixed sulfate-nitrate bath using direct current plating. The electrolytic bath is characterized by the presence of ammonium sulfate which was used as complexing agent to avoid the precipitation of Mn hydroxides. Cyclic voltammetry and chronoamperometry measurements are used to study the reaction mechanisms of the Mn-Bi electrodeposition as a function of the ammonium sulfate concentration and the pH value: the optimized conditions for a stable bath are obtained for 2.5 mol. L-1 of ammonium sulfate and pH 2.3. The Scharifker and Hills (SH) model was used to analyze the current transients at the initial stage of deposition; it was revealed that Mn-Bi electrocrystallization process is governed by three-dimensional nucleation. But as the electrochemical deposition clearly involves the simultaneous presence of the proton cathodic reaction, another model developed by Palomar-Pardave and co. was used to explain the nucleation mechanism and to describe the individual contribution of both the metallic ions and the proton reduction process. The morphology and chemical composition of the films were examined by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The deposits have a cauliflower-shaped appearance with a heterogeneous distribution of manganese and bismuth. The energy dispersive spectroscopy analysis reveals the presence of manganese and bismuth peaks with almost the same relative intensities. The X-rays diffraction analysis shows characteristic peaks of manganese and bismuth. (C) 2014 The Electrochemical Society. All rights reserved.

The effect of zinc and tin addition to pure aluminum was investigated in 3 wt.% NaCl solution. The corrosion behavior of the elaborated samples (Al, Al-Zn and Al-Zn-Sn) was studied by open circuit potential, Tafel plot and electrochemical impedance spectroscopy. For the microstructure characterization, Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy were used. The aluminum activation increases in the following order: Al < Al-5Zn < Al-5Zn-0.1Sn < Al-5Zn-0.2Sn < Al-5Zn-0.4Sn. The impedance measurements and the microscopic observations confirmed the great activity of Al-Zn and Al-Zn-Sn compared to pure Al. The segregation at the grain boundaries leads to intergranular corrosion. (c) 2014 Elsevier Ltd. All rights reserved.

Thermally grown oxide films on carbon steel and titanium were investigated with electrochemical impedance spectroscopy (EIS). EIS data were analyzed in two different ways: by the analysis of imaginary part of the impedance in the high frequency domain and by the electrical equivalent circuit fitting. Three approaches for estimating effective capacitances from constant phase element have been used in this work: Brug, Hsu–Mansfeld formulas and power-law model. The approaches yield different semiconducting characteristics as well as different oxide layer thicknesses.

In the present work, well ordered nanoporous anodic aluminum oxides (AAO) have been prepared on aluminum by a two step anodization process in 0.5 M oxalic acid at various potentials. We report the properties and semiconducting characteristics of the porous alumina barrier layers by electrochemical impedance spectroscopy analysis (EIS). EIS is considered to be a highly sensitive and non-destructive technique that allows determining barrier oxide layer characteristics. Aluminum oxide barrier is considered as a semiconductor which acts as a p-n heterojunction at anodizing voltages up to 20 V. The alumina barrier layer structure consists of a hole transport inner layer and an electron transport outer layer. Doping densities, flatband potential as well as space charge layer thickness are discussed in correlation with anodizing potential. Barrier layer thicknesses measurements obtained by EIS were compared with those obtained after EIS measurements by direct scanning electron microscopy observations. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.068208jes] All rights reserved.