Showing papers in "Journal of Applied Electrochemistry in 2008"
TL;DR: Two triazole derivatives, 3,4-dichloro-acetophenone-O-1'-(1,3,4'-triazolyl)-methaneoxime (4-DTM) and 2,5-Dichloron-acethenone- O-1]-(1',3, 4'-triaxolyl)methANEoxime, were synthesized, and the inhibition effects for mild steel in 1 M HCl solutions were investigated by weight loss measurements, electrochemical tests and scanning electronic microscopy (SEM
Abstract: Two triazole derivatives, 3,4-dichloro-acetophenone-O-1'-(1',3',4'-triazolyl)-methaneoxime (4-DTM) and 2,5-dichloro-acetophenone-O-1'-(1',3',4'-triazolyl)-methaneoxime (5-DTM) were synthesized, and the inhibition effects for mild steel in 1 M HCl solutions were investigated by weight loss measurements, electrochemical tests and scanning electronic microscopy (SEM). The weight loss measurements showed that these compounds have excellent inhibiting effect at a concentration of 1.0 x 10(-3) M. The potentiodynamic polarization experiment revealed that the triazole derivatives are inhibitors of mixed-type and electrochemical impedance spectroscopy (EIS) confirmed that changes in the impedance parameters (R-ct and C-dl) are due to surface adsorption. The inhibition efficiencies obtained from weight loss measurements and electrochemical tests were in good agreement. Adsorption followed the Langmuir isotherm with negative values of the free energy of adsorption Delta G(ads)(o). The thermodynamic parameters of adsorption were determined and are discussed. Results show that both 4-DTM and 5-DTM are good inhibitors for mild steel in acid media.
493 citations
TL;DR: The historical development, current status and future prospects of chlor-alkali electrolysis with oxygen depolarized cathodes (ODCs) are summarized in this paper, and the Finite-gap falling film cells appear to be the technically most mature design among the several ODC electrolysis cells that have been investigated.
Abstract: The historical development, current status and future prospects of chlor-alkali electrolysis with oxygen depolarized cathodes (ODCs) are summarized. Over the last decades, membrane chlor-alkali technology has been optimized to such an extent that no substantial reduction of the energy demand can be expected from further process modifications. However, replacement of the hydrogen evolving cathodes in the classical membrane cells by ODCs allows for reduction of the cell voltage and correspondingly the energy consumption of up to 30%. This replacement requires the development of appropriate cathode materials and novel electrolysis cell designs. Due to their superior long-term stability, ODCs based on silver catalysts are very promising for oxygen reduction in concentrated NaOH solutions. Finite-gap falling film cells appear to be the technically most mature design among the several ODC electrolysis cells that have been investigated.
286 citations
TL;DR: In this article, the efficiency of three heterocyclic compounds, 3-amino-1,2,4-triazole, 4-hydroxy-2H-1-benzopyran-2-one and 4-Hydroxy-3-(1H 1, 2, 4, 4 triazole-3-ylazo)-2H 1-bensopyrans-2.1-one, respectively, as steel corrosion inhibitors in 3.5% NaCl was investigated by Tafel extrapolation and linear polarization methods
Abstract: The efficiency of three heterocyclic compounds, 3-amino-1,2,4-triazole, 4-hydroxy-2H-1-benzopyran-2-one and 4-hydroxy-3-(1H-1,2,4-triazole-3-ylazo)-2H-1-benzopyran-2-one (abbreviated 3-ATA, 4-HQ and 3-ATA-Q, respectively) as steel corrosion inhibitors in 3.5% NaCl has been investigated by Tafel extrapolation and linear polarization methods. Corrosion parameters and adsorption isotherms were determined from current-potential curves. It was found that inhibition efficiencies (η%) and surface coverage (θ) increase with an increase in the concentration of 3-ATA and 3-ATA-Q. However, 4-HQ accelerates the corrosion rate as its concentration increases. The adsorption of 3-ATA and 3-ATA-Q on the steel surface obey Langmuir isotherm. A clear correlation was found between corrosion inhibition efficiency and theoretical parameters obtained by the density functional B3LYP/6-31g(d) method. The experimental results are supported by the theoretical data.
158 citations
TL;DR: In this article, the influence of the PTFE content in commercial Toray graphite paper gas diffusion layer (GDL) on the performance of a PBI-based polymer electrolyte membrane fuel cell (PEMFC) has been studied.
Abstract: The influence of the PTFE content in commercial Toray graphite paper gas diffusion layer (GDL) on the performance of a PBI-based polymer electrolyte membrane fuel cell (PEMFC) has been studied These materials have been characterised by evaluating the porosity, pore size distribution, SEM micrographs, hydrophobicity, air permeability and electrical resistance Fuel cell results show that the lower the Teflon content, the better the cell performance and the lower the losses when oxygen was replaced by air These results led to non-Teflonized carbon paper to be postulated as the most suitable candidate, provided that its mechanical integrity can be maintained throughout the whole process of preparation and testing of the MEA However, some practical problems with this type of commercial non-Teflonized carbon paper were experienced in this work and led to damage of the support The detrimental effects are described and discussed As conclusion, the use of a minimally PTFE-loaded (10%) carbon paper is suggested because the inclusion of this level of Teflon improved properly the mechanical properties of the carbon support and only caused a very small drop in the performance
127 citations
TL;DR: In this paper, the effect of the final potential, time and number of steps on the quantity, distribution and size of the platinum nanoparticles was analyzed through the application of theoretical modelling.
Abstract: Electrodeposition of Pt nanoparticles under potentiostatic conditions was performed on several types of carbon electrode supports: commercial macroporous carbon (a three-dimensional electrode), glassy carbon and graphite. Conducting polymers (poly-aniline and poly-o-aminophenol) were also used. The platinum nanoparticles were obtained by different Potential Step Deposition (PSD) methods in 5 mM H2PtCl6 + 0.5 M H2SO4 aqueous solutions. The effect of the final potential, time and number of steps on the quantity, distribution and size of the platinum nanoparticles was analysed. The mechanism of the electrochemical deposition of platinum was studied through the application of theoretical modelling. The progressive nucleation mechanism provided the closest agreement with the results obtained. In addition, the chemical state and morphology of the electrodeposited materials were determined by means of SEM, TEM and XPS. The results show that the carbon material structure has a strong influence on the Pt particle structure and this, in turn, affects the catalytic activity.
122 citations
TL;DR: In this paper, the authors combined electrochemical and XPS surface analytical methods to gain a deeper insight into the mechanisms underlying the corrosion resistance of electroless deposited Ni-P alloys with phosphorus content between 18 and 22.
Abstract: Electroless Ni–P alloys are produced as coatings on a broad variety of substrates. They exhibit a corrosion resistance that is superior to pure nickel but do not form a NiO oxide film (passive film) as pure nickel does. Despite the fact that many mechanisms have been proposed to explain this superior corrosion behaviour, no consensus has yet been reached. In this work electrochemical and XPS surface analytical methods have been combined in order to gain a deeper insight into the mechanisms underlying the corrosion resistance of electroless deposited Ni–P alloys with phosphorus content between 18 and 22 at.%. The anodic polarization curves in acidic and neutral solutions confirm a broad current plateau followed by a region with increasing current density. During potentiostatic polarization in the plateau region the current decays according to a power law with exponent ca. −0.5 indicating diffusion-limited dissolution of nickel. XPS/XAES measurements performed after potentiostatic polarization show that phosphorus is present in three different chemical environments. Based on the Auger parameter concept and on the chemical state plot, the three phosphorus states were assigned to phosphorus in the bulk alloy, phosphates and an intermediate phosphorus compound attributed to elemental phosphorus. Angle-resolved XPS analysis has shown that the elemental phosphorus is enriched at the interface between the alloy and the outermost surface in contact with the corrosive solution. These results suggest the following conclusions: the high corrosion resistance of electroless deposited Ni–P alloys can be explained by a strong enrichment of elemental phosphorus at the interface which limits the dissolution of nickel via a diffusion mechanism. A complementary explanation––not yet advanced––for the high corrosion resistance may lie in the electronic state of nickel in the Ni–P alloys.
102 citations
TL;DR: In this paper, two disks covered with either boron doped diamond (BDD) or PbO2 were used as anodes in a one compartment flow cell under the same hydrodynamic conditions.
Abstract: This work compares two electrode materials used to mineralize phenol contained in waste waters. Two disks covered with either boron doped diamond (BDD) or PbO2 were used as anodes in a one compartment flow cell under the same hydrodynamic conditions. Efficiencies of galvanostatic electrolyses are compared on the basis of measurements of Total Organic Carbon (TOC) and Chemical Oxygen Demand (COD). Galvanostatic electrolyses were monitored by analysis of phenol and of its oxidation derivatives to evaluate the operating time needed for complete elimination of toxic aromatics. The experimental current efficiency is close to the theoretical value for the BDD electrode. Other parameters being equal, phenol species disappeared at the same rate using the two electrode materials but the BDD anode showed better efficiency to eliminate TOC and COD. Moreover, during the electrolysis less intermediates are formed with BDD compared to PbO2 whatever the current density. A comparison of energy consumption is given based on the criterion of 99% removal of aromatic compounds.
95 citations
TL;DR: In this article, the results of an experimental study on electrochemical disinfection of water are presented, with particular regard to the selectivity of the process towards the production of oxidising agents.
Abstract: The results of an experimental study on electrochemical disinfection of water are presented. Attention was paid to the behaviour of chlorine compounds during electrolysis of water containing chlorides, with particular regard to the selectivity of the process towards the production of oxidising agents. Two reactor configurations were tested: a stirred tank cell and a filter press cell inserted in a hydraulic circuit. Both cells were equipped with boron doped diamond (BDD) anodes. Experiments were performed in batch and continuous mode. The effect of such operating parameters, current density, stirring rate or recirculating flow rate, on the behaviour of the process was investigated. The results at BDD anodes show that low current densities and perfect mixing of the system should be adopted in order to obtain high values of the concentration of oxidising agents avoiding the formation of such undesired by-products as chlorite, chlorate and perchlorate ions. Runs were also performed in which BDD was substituted by a commercial (Ti/RuO2) DSA anode and the results obtained with the two materials are compared.
88 citations
TL;DR: In this paper, the performance of MnOx/C-based electrocatalysts was evaluated in their as-synthesized state and after ageing, either in ambient air for a year (mild ageing) or in an O2-saturated molar KOH solution at 80°C for three weeks (premature ageing).
Abstract: MnOx/C-based electrocatalysts, prepared by the chemical deposition of manganese oxide nanoparticles on carbon, were tested towards the Oxygen Reduction Reaction (ORR) in their as-synthesized state and after ageing, either in ambient air for a year (mild ageing) or in an O2-saturated molar KOH solution at 80 °C for three weeks (premature ageing). For each electrocatalyst, the morphology and composition were characterised using TEM, XRD and chemical analysis. ORR kinetic parameters were evaluated using the Rotating Disk Electrode (RDE) and Rotating Ring Disk Electrode (RRDE) setups. Whilst the oxygen reduction activity of the electrocatalysts barely changes after mild ageing, it decreases after premature ageing following dramatic modifications to both the chemical and crystalline structures of the carbon-supported MnOx nanoparticles. The peroxide yield also sharply increases after premature ageing. Doping MnOx/C with nickel or magnesium divalent cations is beneficial since it improves both the catalytic activity and selectivity towards the 4-electron ORR pathway, even after ageing.
88 citations
TL;DR: In this article, the effect of anode material on the performance of microbial fuel cells (MFC), which utilise oxidisable carbon compounds and other components present in sediments on ocean floors, estuaries and other similar environments is reported.
Abstract: The effect of anode material on the performance of microbial fuel cells (MFC), which utilise oxidisable carbon compounds and other components present in sediments on ocean floors, estuaries and other similar environments is reported. The MFC anode materials were carbon sponge, carbon cloth, carbon fibre, and reticulated vitreous carbon (RVC). Power was produced through the microbial activity at the anode in conjunction with, principally, oxygen reduction at a graphite cloth cathode. After a period of stabilisation, open circuit voltages up to 700 mV were observed for most cells. Steady state polarisations gave maximum power densities of 55 mW m−2 using carbon sponge as the anode; which was nearly twice that achieved with carbon cloth. The latter material typically gave power densities of around 20 mW m−2. The performance of the cell was reduced by operation at a low temperature of 5 °C. Generally, for cells which were capable of generating power at current densities of 100 mA m−2 and greater, mass transport was found to limit both the anode and the cathode performance, due primarily to the low concentrations of electro-active species present or generated in cells.
78 citations
TL;DR: In this article, the authors examined interfacial voiding in solder joints formed with Sn-Ag-Cu solder alloys and electroplated Cu and found that the propensity for voiding could be correlated with specific electroplating parameters.
Abstract: Interfacial voiding in solder joints formed with Sn–Ag–Cu solder alloys and electroplated Cu was examined as a function of the plating solution chemistry and parameters. Galvanostatic Cu plating of ~10 μm thick Cu films was performed in a commercially available plating solution, and in model generic plating solutions. Analysis of the current voltage behavior along with Secondary Ion Mass Spectrometry studies of organic impurity content of two plated and a wrought copper samples, yielded a conclusion that for certain chemistry solutions (e.g., H2SO4 + CuSO4 + Cl− + PEG) and current density ranges above 2.5 mA cm−2, organic impurities were incorporated into the growing Cu. Solder joints were produced with a variety of electroplated Cu samples. These joints were, then, annealed at a temperature of 175 °C for 1 week, cross sectioned and examined. In general, it was observed that interfacial voiding in laboratory electroplated Cu layers was qualitatively similar to the unexplained voiding observed in some industrially plated Cu products. More specifically, it was found that the propensity for voiding could be correlated with specific electroplating parameters that in turn were associated with significant incorporation of organic impurities in the Cu deposit.
TL;DR: In this article, a voltage plateau was observed on the first galvanostatic charging curve of NMC in the extended voltage region positive to 4.5 V vs. Li/Li+ for compounds with x > 0 (overlithiated compounds).
Abstract: Li1+x(Ni1/3Mn1/3Co1/3)1−xO2 (NMC) oxides are among the most promising positive electrode materials for future lithium–ion batteries. A voltage “plateau” was observed on the first galvanostatic charging curve of NMC in the extended voltage region positive to 4.5 V vs. Li/Li+ for compounds with x > 0 (overlithiated compounds). Differences were observed in the cycling stability of the overlithiated and stoichiometric (x = 0) NMC oxides in this potential region. A differential plot of the charge vs. potential profile in the first cycle revealed that, for the overlithiated compounds, a large irreversible oxidative peak arises positive to 4.5 V vs. Li/Li+, while in the same potential region only a small peak due to the electrolyte oxidation is detected for the stoichiometric material. Differential Electrochemical Mass Spectrometry (DEMS) was used to investigate the high voltage region for both compounds and experimental evidence for oxygen evolution was provided for the overlithiated compounds at potentials positive to 4.5 V vs. Li/Li+. No oxygen evolution was detected for the stoichiometric compound.
TL;DR: In this article, the effect of five S-containing amino acids on the corrosion of mild steel in 5% sulfamic acid solution at 40 °C was investigated using potentiodynamic polarization curves and EIS.
Abstract: Rp, potentiodynamic polarization curves and EIS techniques were applied to study the effect of five S-containing amino acids on the corrosion of mild steel in 5% sulfamic acid solution at 40 °C. The compounds are effective inhibitors and the inhibition efficiency follow the order: N-acetylcysteine (ACC) > cysteine (RSH) > S-benzylcysteine (BzC) > cystine (RSSR) ≅ methionine (CH3SR). The inhibitors affect the anodic dissolution of steel by blocking the anodic sites of the surface. EIS measurements indicated that charge transfer is the rate determining step in the absence and presence of the inhibitors and the steel/solution interface can be represented by the equivalent circuit Rs(RctQdl). Adsorption of RSH, CH3SR and RSSR follows the Langmuir model while the Temkin isotherm describes the adsorption of ACC and BzC. From the application of the Flory–Huggins isotherm, the number of water molecules displaced by the adsorbing inhibitor molecules was estimated. The potential of zero charge pzc of mild steel without and with the inhibitors is calculated and the mechanism of corrosion inhibition is discussed in the light of the molecular structure.
TL;DR: In this article, the Pechini-Adams modified method on carbon Vulcan XC-72 was used for the preparation of ternary Pt-based catalysts for ethanol fuel cell.
Abstract: Binary and ternary Pt-based catalysts were prepared by the Pechini–Adams modified method on carbon Vulcan XC-72, and different nominal compositions were characterized by TEM and XRD. XRD showed that the electrocatalysts consisted of the Pt displaced phase, suggesting the formation of a solid solution between the metals Pt/W and Pt/Sn. Electrochemical investigations on these different electrode materials were carried out as a function of the electrocatalyst composition, in acid medium (0.5 mol dm−3 H2SO4) and in the presence of ethanol. The results obtained at room temperature showed that the PtSnW/C catalyst display better catalytic activity for ethanol oxidation compared to PtW/C catalyst. The reaction products (acetaldehyde, acetic acid and carbon dioxide) were analyzed by HPLC and identified by in situ infrared reflectance spectroscopy. The latter technique also allowed identification of the intermediate and adsorbed species. The presence of linearly adsorbed CO and CO2 indicated that the cleavage of the C–C bond in the ethanol substrate occurred during the oxidation process. At 90 °C, the Pt85Sn8W7/C catalyst gave higher current and power performances as anode material in a direct ethanol fuel cell (DEFC).
TL;DR: In this paper, Pd-PEDOT films were synthesized through an electrochemical route and characterized using scanning electron microscopy and atomic force microscopy (AFM) techniques.
Abstract: Palladium (Pd) incorporated poly (3,4-ethylenedioxythiophene) (PEDOT) films were synthesized through an electrochemical route and characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The electrochemical study showed catalytic oxidation of dopamine (DA) with optimum loading of Pd. DA and uric acid (UA) were detected using differential pulse voltammetry (DPV). In the presence of ascorbic acid (AA), DA-AA showed peak potential separation of 0.19 V while 0.32 V between UA-AA on Pd-incorporated PEDOT. These peak separations are large enough for sensing DA and UA in the presence of AA. DA and UA exhibited linear calibration plots and the minimum detection limits are 0.5 and 7 µM respectively. On Pd-PEDOT, the reversibility of DA oxidation was found to increase compared to bare glassy carbon electrode (GCE) and PEDOT modified GCE. Fouling effects were also found to be minimal making Pd-PEDOT composite suitable for electroanalysis.
TL;DR: In this paper, the anodic polarization intervals suppressed the deposition of poisoning species on the electrode, and the amount of two hydrocarbons produced, CH4 and C2H6, decreased only slightly even after one hour.
Abstract: Although the electrochemical reduction of CO2 at a copper electrode produces hydrocarbons, the activity for the conversion of CO2 is significantly reduced after several tens of minutes by the deposition of poisoning species on the electrode. In order to solve the poisoning species problem, the electrochemical reduction of CO2 was carried out using a copper electrode in the pulse electrolysis mode by anodic as well as cathodic polarization. The anodic polarization intervals suppressed the deposition of the poisoning species on the electrode, and the amount of two hydrocarbons produced, CH4 and C2H6, decreased only slightly even after one hour. By choosing the appropriate anodic potential and time duration the selectivity for C2H6 formation was significantly enhanced. The enhancement was found to be due to the copper oxide formed on the copper electrode. The selectivity was further improved when the electrochemical reduction was carried out using a copper oxide electrode. The highest efficiency of about 28% was obtained at −3.15 V.
TL;DR: In this paper, composite ceramic coatings were formed on aluminium by AC plasma electrolytic oxidation (PEO) using Na6P6O18 or Na2SiO3/5H2O/KOH electrolytes with monoclinic zirconia nanoparticles in suspension.
Abstract: Composite ceramic coatings were formed on aluminium by AC plasma electrolytic oxidation (PEO) using Na6P6O18 or Na2SiO3 · 5H2O/KOH electrolytes with monoclinic zirconia nanoparticles in suspension. The coatings grown in Na2SiO3 · 5H2O/KOH electrolyte revealed γ-Al2O3 and amorphous phase; α-Al2O3 and AlPO4 were additionally produced with the Na6P6O18 electrolyte. Higher temperature zirconia phases, possibly tetragonal and orthorhombic, in addition to the monoclinic phase, were indicative of elevated temperatures at sites of microdischarges. Further, local melting resulted in zirconium-rich dendrites in the coating formed in silicate electrolyte. Zirconium was mainly located in the relatively compact, outer layer of the coating, constituting ∼70–90% of the coating thickness. Nanoparticles appeared to be incorporated at the coating surface and following transport to the interface regions between the inner and outer layers along short-circuit paths through the outer coating.
TL;DR: In this article, the corrosion behavior of AZ91D and NZ30K alloys was investigated in 5% NaCl solution by immersion tests and electrochemical measurements, and it was shown that the corrosion rate of NZ30k was about half that of Z91D.
Abstract: The corrosion behaviour of AZ91D and NZ30K (Mg–3Nd–0.2Zn–0.4Zr) alloys was investigated in 5% NaCl solution by immersion tests and electrochemical measurements. The immersion tests showed that the corrosion rate of NZ30K was about half that of AZ91D. The localized corrosion of AZ91D was more severe than that of NZ30K due to the higher cathode-to-anode area ratio and higher difference in potential of the cathode phase and the anode matrix. The corrosion of AZ91D concentrated on certain areas and resulted in much deeper corrosion pits, whilst that of NZ30K spread across the surface and led to more uniform and shallow corroded areas. The corrosion products of NZ30K were more compact than those of AZ91D as indicated by SEM. The cyclic polarization curves showed that NZ30K had higher pitting corrosion resistance than AZ91D.
TL;DR: In this paper, the adsorption and corrosion inhibition behavior of four selected piperidine derivatives at nickel in 1.0 M HNO3 solution were studied computationally by molecular dynamics simulation and quantum chemical calculations and electrochemically by Tafel and impedance methods.
Abstract: The adsorption and corrosion inhibition behaviour of four selected piperidine derivatives, namely piperidine (pip), 2-methylpiperidine (2mp), 3-methylpiperidine (3mp), and 4-methylpiperidine (4mp) at nickel in 1.0 M HNO3 solution were studied computationally by the molecular dynamics simulation and quantum chemical calculations and electrochemically by Tafel and impedance methods. The results indicate a strong dependence of the inhibition performance on the nature of the metal surface, in addition to the structural effects of piperidines. Inhibition is accomplished by adsorption of piperidines on the metal surface without detectable changes in the chemistry of corrosion. Adsorption is predominantly chemisorptive in the active region and by hydrogen bond formation in the passive region. The potential of zero charge (PZC) of the nickel electrode was determined in 1.0 M HNO3 solutions in the absence and presence of 10−2 M 2mp, and the electrostatic (physical) adsorption was discussed. The inhibition efficiency of these compounds increases in the order: 4mp > 3mp > 2mp > pip. Molecular simulation studies were applied to optimize the adsorption structures of piperidine derivatives. The nickel/inhibitor/solvent interfaces were simulated and the charges on the inhibitor molecules as well as their structural parameters were calculated in the presence of solvent effects. Quantum chemical calculations based on the ab initio method were performed to determine the relationship between the molecular structure of piperidines and their inhibition efficiency. Results obtained from Tafel and impedance methods are in good agreement and confirm theoretical studies.
TL;DR: In this article, the sulfonamide antibiotic sulfamethoxazole (SMX) was oxidized at a boron-doped diamond anode, at which reactive hydroxyl radicals are formed.
Abstract: Pharmaceutical residues in the aquatic environment represent an emerging environmental problem, because many pharmaceuticals are refractory towards conventional waste water treatment. This study focussed on the oxidation of the sulfonamide antibiotic sulfamethoxazole (SMX) at a boron-doped diamond anode, at which reactive hydroxyl radicals are formed. Electrochemical oxidation led to mineralization with high current efficiency, but without the formation of known toxic products of partial oxidation. A “mixed” kinetic order with respect to substrate concentration was observed; the kinetics could be shifted in the direction of either diffusion control (first order in SMX) or current control (zero order in SMX) by adjusting the substrate concentration and current density. Alternatively, the electrooxidation could be described by a model, applicable to a wide range of reaction conditions, in which the kinetic orders with respect to current and initial substrate concentration were approximately 0.4 and 0.5, respectively.
TL;DR: In this paper, Ni-Co nanocrystalline coatings were electrodeposited onto a carbon steel substrate with and without saccharin addition, and it was shown that the Ni-co grain size is not reduced by the nucleation rate.
Abstract: Nickel–Co nanocrystalline coatings were electrodeposited onto a carbon steel substrate with and without saccharin addition. In the absence of saccharin, current density and adsorption of hydrogen complexes and/or intermediate components were distinguished as two effective parameters causing nanocrystalline electrodeposits. In the latter case, the growth active sites can be blocked easily at low current densities. By increasing the current density, a lower degree of adsorption was associated by a significant increase in surface diffusion of adions resulting in grain growth. Although, the nucleation rate is expected to increase with current density, it seems that the Ni–Co grain size is not reduced by the nucleation rate. Adsorption of saccharin molecules and/or decomposed sulfide species occurred in the saccharin contained bath, resulting in slow surface diffusion of adions. Therefore, finer grains were obtained which produced a smooth morphology instead of the pyramidal forms obtained in the absence of saccharin.
TL;DR: In this paper, the electrochemical properties of bare and Co3(PO4)2-coated LiNi0.8Co0.16Al0.04O2 electrodes after high current damage testing were characterized.
Abstract: The electrochemical properties of bare and Co3(PO4)2-coated LiNi0.8Co0.16Al0.04O2 electrodes after high current damage testing were characterized. Damage was induced by cycling with a high current density of 600 m Ag−1. Co3(PO4)2-coated LiNi0.8Co0.16Al0.04O2 electrodes exhibit lower capacity loss and better charge retention than bare LiNi0.8Co0.16Al0.04O2 electrodes after damage testing. The discharge capacity reduction of bare and Co3(PO4)2-coated electrodes after damage testing were ∼27 and 15%, respectively. The impedance of cells containing bare electrodes remarkably increased after high current cycling, which may be induced by damage to the electrode surface. However, damage was successfully suppressed by the Co3(PO4)2 coating. Bare LiNi0.8Co0.16Al0.04O2 electrodes developed large amounts of cracks and other extended defects after high current cycling. In contrast, Co3(PO4)2-coated electrodes maintained stable features after high current cycling, indicating the coating layer effectively protected the surface of the LiNi0.8Co0.16Al0.04O2 powder.
TL;DR: In this paper, a thin film of poly(l-serine) was prepared via electropolymerization for the determination of trace levels of estradiol in blood serum.
Abstract: A thin film of poly(l-serine) was prepared via electropolymerization for the determination of trace levels of estradiol. In pH 5.0 phosphate buffer, l-serine was oxidized during the cyclic potential sweeps between −0.60 and 2.0 V, forming a thin film at the electrode surface. The electrochemical behavior of estradiol was investigated. The oxidation peak potential of estradiol shifts negatively at the poly(l-serine) film-coated glassy carbon electrode (GCE) compared with that at the bare GCE. Otherwise, the oxidation peak current greatly increases at the poly(l-serine) film-modified GCE. These phenomena suggest that the poly(l-serine) film exhibits catalytic activity towards the electrochemical oxidation of estradiol. Based on this, a sensitive, rapid and simple electrochemical method was proposed for the determination of estradiol. The limit of detection is evaluated to be 2.0 × 10−8 mol L−1. Finally, this method was successfully used to determine estradiol in blood serum.
TL;DR: In this article, RuO2 and Ta2O5 thin films containing between 10 and 90 at% Ru were prepared by the Pechini-Adams method, which can profoundly affect the structural and electrochemical properties of electrocatalytic coatings.
Abstract: Preparation methods can profoundly affect the structural and electrochemical properties of electrocatalytic coatings In this investigation, RuO2–Ta2O5 thin films containing between 10 and 90 at% Ru were prepared by the Pechini–Adams method These coatings were electrochemically and physically characterized by cyclic voltammetry, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) The composition and morphology of the oxide were investigated before and after accelerated life tests (ALT) by EDX and SEM SEM results indicate typical mud-flat-cracking morphology for the majority of the films High resolution SEMs reveal that pure oxide phases exhibit nanoporosity while binary compositions display a very compact structure EDX analyses reveal considerable amounts of Ru in the coating even after total deactivation XRD indicated a rutile-type structure for RuO2 and orthorhombic structure for Ta2O5 XPS data demonstrate that the binding energy of Ta is affected by Ru addition in the thin films, but the binding energy of Ru is not likewise influenced by Ta The stability of the electrodes was evaluated by ALT performed at 750 mA cm−2 in 80 °C 05 mol dm−3 H2SO4 The performance of electrodes prepared by the Pechini–Adams method is 100% better than that of electrodes prepared by standard thermal decomposition
TL;DR: In this article, the electrochemical oxidation of an aqueous solution containing mecoprop (2-(2-methyl-4-chlorophenoxy)propionic acid) has been studied at PbO2 anodes by cyclic voltammetry and bulk electrolysis.
Abstract: The electrochemical oxidation of an aqueous solution containing mecoprop (2-(2-methyl-4-chlorophenoxy)propionic acid) has been studied at PbO2 anodes by cyclic voltammetry and bulk electrolysis. The influence of current density, hydrodynamic conditions, temperature and pH on the degradation rate and current efficiency is reported. The results obtained show that the use of PbO2 leads to total mineralization of mecoprop due to the production of oxidant hydroxyl radical electrogenerated from water discharge. The current efficiency for the electro-oxidation of mecoprop is enhanced by low current density, high recycle flow-rates and high temperature. In contrast, the pH effect was not significant. It has also been observed that mecoprop decay kinetics follows a pseudo-first-order reaction and the rate constant increases with rising current density.
TL;DR: In this paper, the Pt-Ru catalyst was used for methanol electrooxidation in the presence of chloroplatinic acid and ruthenium chloride, and three different compositions were analyzed in the range 0.20 at.% Ru content.
Abstract: Methanol electrooxidation was investigated on Pt–Ru electrocatalysts supported on glassy carbon. The catalysts were prepared by electrodeposition from solutions containing chloroplatinic acid and ruthenium chloride. Bulk composition analysis of the Pt–Ru catalyst was performed using an X-ray detector for energy dispersive spectroscopy analysis (EDX). Three different compositions were analyzed in the range 0–20 at.% Ru content. Tafel plots for the oxidation of methanol in solutions containing 0.1–2 M CH3OH, and in the temperature range 23–50 °C showed a reasonably well-defined linear region. The slope of the Tafel plots was found to depend on the ruthenium composition. The lower slope was determined for the Pt catalyst, varying between 100 and 120 mV dec−1. The values calculated for the alloys were higher, ranging from 120 to 140 mV dec−1. The reaction order for methanol varies from 0.5 to 0.8, increasing with the ruthenium content. The activation energy calculated from Arrhenius plots was found to change with the catalyst composition, showing a lower value around 30 kJ mol−1 for the alloys, and a higher value, of 58.8 kJ mol−1, for platinum. The effect of ruthenium content is explained by the bifunctional reaction mechanism.
TL;DR: In this article, the corrosion inhibition characteristics of N′-[(1E)-(4-hydroxy phenyl) methylene] isonicotinohydrazide (HIH) and N′[1E]-(4,hydroxyl-3-methoxy phenyl)-methylene]-isonic-methylene [HMIH on mild steel corrosion in 1M hydrochloric acid were investigated by weight loss, potentiodynamic polarization and impedance techniques.
Abstract: The corrosion inhibition characteristics of N′-[(1E)-(4-hydroxy phenyl) methylene] isonicotinohydrazide (HIH) & N′-[(1E)-(4-hydroxyl-3-methoxy phenyl) methylene] isonicotinohydrazide (HMIH) on mild steel corrosion in 1 M hydrochloric acid were investigated by weight loss, potentiodynamic polarization and impedance techniques. The inhibition efficiency increased with increase in inhibitor concentration but decreased with increase in temperature. The thermodynamic functions of dissolution and adsorption processes were evaluated. The polarization measurements indicated that the inhibitors are of mixed type. The adsorption of the compounds was found to obey Langmuir’s adsorption isotherm. Passive film characterization was done by Fourier transform infrared (FTIR) spectra and scanning electron microscopy (SEM).
TL;DR: In this article, the electrochemical behavior of the complexation of cerium(IV) with EDTA and DTPA was studied using both cyclic voltammetry (CV) and rotating disc electrode (RDE).
Abstract: The electrochemical behaviour of the complexation of cerium(IV) with EDTA and DTPA was studied using both cyclic voltammetry (CV) and rotating disc electrode (RDE). The Ce(IV)–DTPA complex at various scan rates gave a linear correlation between the peak potential (Ep) and square root of scan rate, showing that the kinetics of the overall process was controlled by mass transport. However, when the EDTA ligand was added to the Ce(IV) there was no specific change to the potential peak, i.e. the Ce(IV)–EDTA complex has the same redox potential as the Ce(IV)/(III) couple. Kinetic parameters such as potential, limiting current, diffusion coefficients, transfer coefficient and rate constants were studied. The results from RDE experiments confirmed that the parameters measured by CV are similar under hydrodynamic conditions and can be used to determine the kinetic parameters of the redox couples. The use of DTPA as a ligand for complexation of Ce(IV) gaves more favourable results compared to the Ce–(EDTA) complex reported previously. The results of kinetic studies of Ce(IV)–DTPA complex shows promise as an electrolyte for redox flow battery.
TL;DR: In this paper, a qualitative description of the influence of applied current density and the nitrogen-to-chlorine ratio N/Cl on the distribution of urea electroxidation by-products was obtained.
Abstract: The direct oxidation of urea at high electrode potentials over platinized titanium electrodes in sulphate media generates a high amount of nitrates, representing an environmental problem. Coupling direct and indirect oxidation (using chloride salt), the total amount of generated nitrates can be lowered due to competition between anodic generation of chlorine and nitrates. A qualitative description of the influence of applied current density (ranging from 0.5 to 30 A m−2) and the nitrogen-to-chlorine ratio N/Cl (ranging from 0.5 to 3 by weight) on the distribution of urea electroxidation by-products was obtained. In a highly acidic environment, a decrease in nitrate concentration was observed when operating at relatively high current densities, which suggests the occurrence of a complex heterogeneous reaction involving nitrates and yielding mainly molecular nitrogen.