ISRN Electrochemistry The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Theoretical Analysis of an Amperometric Biosensor Based on Parallel Substrates Conversion Thu, 10 Apr 2014 07:48:29 +0000 The behaviour of an amperometric biosensor based on parallel substrates conversion for steady-state condition has been discussed. This analysis contains a nonlinear term related to enzyme kinetics. Simple and closed form of analytical expressions of concentrations and of biosensor current is derived. This model was originally reported by Vytautas Aseris and his team (2012). Concentrations of substrate and product are expressed in terms of single dimensionless parameter. A new approach to Homotopy perturbation method (HPM) is employed to solve the system of nonlinear reaction diffusion equations. Furthermore, in this work, the numerical solution of the problem is also reported using Matlab program. The analytical results are compared with the numerical results. The analytical result provided is reliable and efficient to understand the behavior of the system. T. Praveen and L. Rajendran Copyright © 2014 T. Praveen and L. Rajendran. All rights reserved. A CV Study of Copper Complexation with Guanine Using Glassy Carbon Electrode in Aqueous Medium Wed, 02 Apr 2014 13:40:19 +0000 Voltammetric behaviors of Copper (II) nitrogen bearing nucleobases, such as Guanine (C5H4N5O2) was studied in electro analyzer using cyclic voltammetry (CV) on a Glassy Carbon Electrode. Assessment of the chemical and physical conditions that may favor optimum current enhancement was done by studying the effect of variation of concentration of metal and ligand ions, variation of scan rate, variation of step height, variation of pH values, and variation of supporting electrolyte as (NH4)2SO4, KCl, and NaCl. It was observed that Copper and Guanine forms a 1 : 2 ratio complex. The work reflects that increasing the concentration of either metal ion or ligand ion increases the corresponding current. Increasing the scan rate increases the corresponding current linearly with the square root of the scan rate. As the step height decreases the peaks become sharp. Anodic and cathodic current increases linearly with decreasing step height. For the complex mixture the complexation occurs maximum at a pH of 2.3–7.0 and is badly restricted in the slightly alkaline medium and the complexing order of the supporting electrolyte showed a trend as . Md. Sohel Rana, Mohammad Arifur Rahman, and A. M. Shafiqul Alam Copyright © 2014 Md. Sohel Rana et al. All rights reserved. Reduced Graphene Oxide Supported Antimony Species for High-Performance Supercapacitor Electrodes Wed, 05 Mar 2014 08:35:03 +0000 Antimony species was chemically anchored on graphene oxide using antimony (III) chloride precursor and then converted to the reduced graphene oxide-antimony species composite by a well-established polyol method. The resultant composite was successfully used as supercapacitor electrodes in a two-electrode symmetric system with aqueous electrolyte. The specific capacitance calculated from the galvanostatic charge/discharge curves obtained for this composite was 289 F/g. The enhanced capacitance results were confirmed by the electrochemical impedance spectroscopy and cyclic voltammetry. The high capacitance of the reduced graphene oxide-antimony species composite arises from the combination of double-layer charging and pseudocapacitance caused by the Faradaic reactions of the intercalated antimony species and residual surface-bonded functional groups. Mateusz Ciszewski, Andrzej Mianowski, Ginter Nawrat, and Piotr Szatkowski Copyright © 2014 Mateusz Ciszewski et al. All rights reserved. Enhanced Structural Integrity and Electrochemical Performance of AlPO4-Coated MoO2 Anode Material for Lithium-Ion Batteries Tue, 04 Mar 2014 07:51:50 +0000 AlPO4 nanoparticles were synthesized via chemical deposition method and used for the surface modification of MoO2 to improve its structural stability and electrochemical performance. Structure and surface morphology of pristine and AlPO4-coated MoO2 anode material were characterized by electron microscopy imaging (SEM and TEM) and X-ray diffraction (XRD). AlPO4 nanoparticles were observed, covering the surface of MoO2. Surface analyses show that the synthesized AlPO4 is amorphous, and the surface modification with AlPO4 does not result in a distortion of the lattice structure of MoO2. The electrochemical properties of pristine and AlPO4-coated MoO2 were characterized in the voltage range of 0.01–2.5 V versus Li/Li+. Cyclic voltammetry studies indicate that the improvement in electrochemical performance of the AlPO4-coated anode material was attributed to the stabilization of the lattice structure during lithiation. Galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS) studies reveal that the AlPO4 nanoparticle coating improves the rate capability and cycle stability and contributes toward decreasing surface layer and charge-transfer resistances. These results suggest that surface modification with AlPO4 nanoparticles suppresses the elimination of oxygen vacancies in the lattice structure during cycling, leading to a better rate performance and cycle life. José I. López-Pérez, Edwin O. Ortiz-Quiles, Khaled Habiba, Mariel Jiménez-Rodríguez, Brad R. Weiner, and Gerardo Morell Copyright © 2014 José I. López-Pérez et al. All rights reserved. Electrodialysis of Phosphates in Industrial-Grade Phosphoric Acid Thu, 19 Dec 2013 15:35:34 +0000 The objective of this research was to study the purification of industrial-grade phosphoric acid (P2O5) by conventional electrodialysis. The experiments were conducted using a three-compartment cell with anion and cation membranes, and industrial acid solution was introduced into the central compartment. The elemental analysis of the diluted solution indicated that the composition of magnesium, phosphates, and sodium was reduced in the central compartment. The ratios of the concentration of the ions and the phosphates were essentially unchanged by the process. Consequently, electrodialysis could not purify the acid in the central compartment, and the migration of phosphate ions to the anolyte produced a highly concentrated phosphoric acid solution containing sulfates and chlorides as impurities. However, the migration of the phosphate ions across the membrane consumed a large amount of energy. Detailed speciation diagrams were constructed in this study. These diagrams showed that metal-phosphate complexes were predominant in the industrial phosphoric acid solution. This result explains why the ratios of the concentrations of the ion metals and the phosphates did not change in the purification process. The energy consumed in the electrodialysis indicated that the metal-phosphate complexes were less mobile than the free-phosphate ions. The speciation diagrams explained the experimental results satisfactorily. J. J. Machorro, J. C. Olvera, A. Larios, H. M. Hernández-Hernández, M. E. Alcantara-Garduño, and G. Orozco Copyright © 2013 J. J. Machorro et al. All rights reserved. Electrochemical and Surface Morphological Studies of Carbon Steel Corrosion by a Novel Polynuclear Schiff Base in HCl Solution Mon, 02 Dec 2013 10:14:12 +0000 The corrosion inhibition efficiency of a potential polynuclear Schiff base, (s)-2-(anthracene-9 (10H)-ylidene amino)-5-guanidinopentanoic acid (A9Y5GPA), on carbon steel (CS) in 1 M hydrochloric acid solution has been investigated using weight loss measurements, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization studies. The corrosion inhibition efficiencies of parent amine [(s)-2-amino-5-guanidinopentanoic acid] and parent ketone (anthracene-9 (10H)-one) on carbon steel in 1.0 M hydrochloric acid solution have also been investigated using weight loss studies. The electrochemical and weight loss data established that the inhibition efficiency on CS increases with the increase in the concentration of inhibitor, A9Y5GPA. The adsorption of A9Y5GPA obeys the Langmuir adsorption isotherm. Thermodynamic parameters (, ) were calculated using the adsorption isotherm. Activation parameters of the corrosion process (, and ) were also calculated from the corrosion rates obtained from temperature studies. Tafel plot analysis revealed that A9Y5GPA acts as a mixed-type inhibitor. A probable inhibition mechanism was also proposed. Surface morphology of the carbon steel specimens in the presence and absence of the inhibitor was evaluated by SEM analysis. K. S. Shaju, K. Joby Thomas, Vinod P. Raphael, and Aby Paul Copyright © 2013 K. S. Shaju et al. All rights reserved. An Immunosensor for Pathogenic Staphylococcus aureus Based on Antibody Modified Aminophenyl-Au Electrode Sun, 10 Nov 2013 15:34:10 +0000 The objective of this work is to elaborate an immunosensing system which will detect and quantify Staphylococcus aureus bacteria. A gold electrode was modified by electrografting of 4-nitrophenyl diazonium, in situ synthesized in acidic aqueous solution. The immunosensor was fabricated by immobilizing affinity-purified polyclonal anti S. aureus antibodies on the modified gold electrode. Cyclic voltammetry (CV) and Faradaic Electrochemical Impedance Spectroscopy (EIS) were employed to characterize the stepwise assembly of the immunosensor. The performance of the developed immunosensor was evaluated by monitoring the electron-transfer resistance detected using Faradaic EIS. The experimental results indicated a linear relationship between the relative variation of the electron transfer resistance and the logarithmic value of S. aureus concentration, with a slope of 0.40 ± 0.08 per decade of concentration. A low quantification limit of  CFU per ml and a linear range up to  CFU per mL were obtained. The developed immunosensors showed high selectivity to Escherichia coli and Staphylococcus saprophyticus. Amani Chrouda, Mohamed Braiek, Karima Bekir Rokbani, Amina Bakhrouf, Abderrazak Maaref, and Nicole Jaffrezic-Renault Copyright © 2013 Amani Chrouda et al. All rights reserved. Electrochemical Behavior of Malachite Green in Aqueous Solutions of Ionic Surfactants Mon, 30 Sep 2013 14:11:28 +0000 Electrochemical behavior of malachite green (MG) oxalate in aqueous solution was studied in the presence of a cationic surfactant, cetyltrimethylammonium bromide (CTAB), and an anionic surfactant, sodium dodecyl sulfate (SDS) at a glassy carbon electrode using cyclic voltammetry. The electrochemical oxidation of MG has been characterized as an electrochemically irreversible diffusion-controlled process. Oxidative peak current sharply decreased with increasing SDS concentration, while a slight increase with increasing [CTAB] was apparent. The apparent diffusion coefficient, the surface reaction rate constant, and the electron transfer coefficient of MG clearly show correlation of the electrochemical behavior with the dissolved states of the surfactants. Electrochemical observations together with spectrophotometric results at varying surfactant concentrations provide evidence of interaction of MG with the surfactants to varying extent depending on the type of the surfactant and the concentration. Mohammad Mijanur Rahman, M. Yousuf A. Mollah, M. Muhibur Rahman, and Md. Abu Bin Hasan Susan Copyright © 2013 Mohammad Mijanur Rahman et al. All rights reserved. Corrosion Protection of AA7075 Aluminium Alloy by Trimethoxy-Silanes Self-Assembled Monolayers Tue, 02 Apr 2013 15:08:13 +0000 This study presents electrochemical data concerning the aluminium alloy AA7075 surface modified by self-assembled monolayers (SAMs) of octadecyl-trimethoxy-silane and propyl-trimethoxy-silane. Polarisation curves have shown SAMs blocking effect, as they partially block the oxygen reduction reaction and displace the corrosion potential to positive values. Electrochemical impedance spectroscopy experiments have suggested that the protective effect comes from the oxide layer stabilization by the organic monolayers, which block the corroding species diffusion to the surface. These results show the potential of using methoxy-silanes SAMs as corrosion protective coatings; however, they are also indicative of the superior octadecyl-trimethoxy-silane protective characteristics. Rodrigo S. Neves, Daiane P. B. Silva, and Artur J. Motheo Copyright © 2013 Rodrigo S. Neves et al. All rights reserved. Inhibition of Mild Steel Corrosion in Sulphuric Acid Using Esomeprazole and the Effect of Iodide Ion Addition Sun, 31 Mar 2013 13:48:44 +0000 The inhibition of the corrosion of mild steel in 1 M H2SO4 solution by the pharmaceutically active compound esomeprazole (ESP) has been investigated by using weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy measurements. The effect of temperature on the corrosion behavior with the addition of different concentrations of ESP was studied in the temperature range of 30–60°C. Results obtained revealed that the inhibition efficiency increased with the increase in concentration of the inhibitor but decreased with the increase in temperature. The addition of KI increased the inhibition of ESP to a considerable extent. The experimental results suggest that the presence of iodide ions in the solution stabilized the adsorption of the ESP molecule on the mild steel surface, thereby improving the inhibition efficiency. Polarization curves indicated that the ESP belonged to a mixed-type inhibitor. Adsorption of the inhibitor on the mild steel surface is found to obey the Langmuir adsorption isotherm. Some thermodynamic functions of dissolution and adsorption processes were also determined. Surface analysis via scanning electron microscope (SEM) and atomic force microscope (AFM) shows a significant improvement in the surface morphology of the mild steel plate. G. Karthik and M. Sundaravadivelu Copyright © 2013 G. Karthik and M. Sundaravadivelu. All rights reserved. Pulse-Current Electrodeposition for Loading Active Material on Nickel Electrodes for Rechargeable Batteries Tue, 12 Mar 2013 17:29:34 +0000 Although the pulse-current electrodeposition method is a commonly used technique, it has not been widely employed in electrode preparation. This method was applied to sintered nickel electrodes in a nickel salt solution containing additives. The active material that was obtained, nickel hydroxide, was studied using different characterization techniques. Electrodes impregnated with pulse current had higher capacity than those impregnated with continuous current. The active material is homogeneous and compact with optimum loading and good performance during discharge. These characteristics would provide a large amount of energy in a short time due to an increase in the electrode kinetic reaction. M. D. Becker, G. N. Garaventta, and A. Visintin Copyright © 2013 M. D. Becker et al. All rights reserved. Cyclic Voltammetric Investigations of Thiazine Dyes on Modified Electrodes Tue, 12 Feb 2013 18:43:01 +0000 Electrochemical behavior of five progressively alkylated thiazine dyes has been investigated at glassy carbon/montmorillonite and glassy carbon/zeolite electrodes. Quantitative characteristics, associated with the positions of peak potentials ( and ) and current ratios (), are measured with scan rates. The peak current observed in the modified electrodes is dependent on both the porosity and nature and number of sites involved in partitioning the complex into film. The values of diffusion coefficient for different dyes have been calculated from electrochemical data. It is suggested that in clay-modified electrode along with physical diffusion the process of electron hopping seems to be most likely. Amitabha Chakraborty, Shamsuzzaman Ahamed, Subrata Pal, and Swapan K. Saha Copyright © 2013 Amitabha Chakraborty et al. All rights reserved. Determination of Mobility and Charge Carriers Concentration from Ionic Conductivity in Sodium Germanate Glasses above and below Mon, 11 Feb 2013 15:46:24 +0000 The ionic conductivity and viscous flow data of , , have been collected in a large temperature range, below and above their glass transition temperatures (). A microscopic model is proposed, assuming that the ionic displacement would result from the migration of interstitial positively charged cationic pairs whose concentration is an activated function of temperature. Below , their migration is also an activated mechanism, but a “free volume” would prevail above this temperature. This discontinuity in the migration mechanism justifies a Dienes-Macedo-Litovitz (DML) relationship to be representative of conductivity data above and an Arrhenius law below. According to this model, the enthalpy deduced by the fit of high temperature data using a DML equation would correspond to the charge carrier formation, whose migration enthalpy, below , could be deduced by the difference between the activation energy measured in the Arrhenius domain and the charge carrier formation enthalpy. To reduce the number of adjustable parameters numerical values were physically justified. We also applied a complete test for conductivity below , using the so-called weak electrolyte model, splitting activation enthalpy into formation and migration enthalpies and also explaining the variation of pre-exponential term of conductivity with composition. Marcio Luis Ferreira Nascimento Copyright © 2013 Marcio Luis Ferreira Nascimento. All rights reserved. Influence of Surfactants on the Characteristics of Nickel Matrix Nanocomposite Coatings Sun, 03 Feb 2013 13:39:11 +0000 Nickel-based nanocomposite coatings were prepared from a Watts-type electrolyte containing reinforcement’s particles (silicon carbide and graphite) to deposit onto the steel St-37 substrate. The electrochemical plating of the coatings in absence and presence of surfactants and reinforcements particles was carried out to optimize high quality coatings with appropriate mechanical and morphological features. The surfactants such as cetyltrimethylammonium bromide (CTAB), sodyumdodecyl sulfate (SDS), and saccharine affected electrodeposition plating and subsequently changed mechanical characteristics. Based on XRD results, the dominant phases in the absence of surfactants were nickel oxide (NiO), nickel, and silicon carbide (SiC), while the main phases in presence of surfactants were nickel (Ni) and SiC. The hardness of the resultant coatings was found to be from 332 to 593 (Hv) depending on the bath parameter and the reinforcements weight percentage (wt%) in the Ni matrix. Microscopic observations illustrated a cluster-like structure which consisted of some fine sphere particulates with average particle size of 65–150 nm. According to elemental mapping spectra, a homogenous distribution of nickel, silicon, and carbon particles appeared into the nickel matrix coating. Finally, the experimental outcomes demonstrated that the surfactants have significant influence on the composition of coatings, surface morphology, and mechanical properties. Abbas Fahami, Bahman Nasiri-Tabrizi, Mohsen Rostami, and Reza Ebrahimi-Kahrizsangi Copyright © 2013 Abbas Fahami et al. All rights reserved. A Study of the Initial Stages of Co Deposition on a Silver Electrode in Ammonia Medium Using an Electrochemical Quartz Crystal Microbalance Thu, 31 Jan 2013 07:51:23 +0000 The early stages of Co deposition on a silver electrode in ammonia medium were studied using cyclic voltammetry and chronoamperometry coupled with quartz crystal microbalance (EQCM) in ammonia solution. The results obtained by means of EQCM showed that during the initial stages of cobalt deposition a monolayer is formed on the substrate both in the underpotential and overpotential region, and this monolayer is formed at −600 mV and −980 mV. Once the cobalt deposition process starts, the growth is very fast making the investigation of the initial stages rather difficult. During this process, cobalt atoms transfer their two electrons through free species and not through cobalt hydroxide species adsorbed on the electrode as CoOH+ or Co(OH)2. In addition, it has been found that at potentials more positive than −600 mV, ammonia adsorption takes place on the substrate surface, and theses species are replaced when the cobalt atoms arrive at potentials more negative than −600 mV. A. Montes-Rojas and A. L. Donjuan-Medrano Copyright © 2013 A. Montes-Rojas and A. L. Donjuan-Medrano. All rights reserved. Improved Performance of Hydrothermally Synthesized by Ball Milling as a Positive Electrode for Li Ion Battery Mon, 28 Jan 2013 08:20:26 +0000 LiMnPO4 is anticipated to be a promising cathode material for next generation lithium battery. A reduction of particle size is recognized as a good strategy to improve its performance and it can be achieved by ball milling. However, the ball milling including carbon addition forms small LiMnPO4 particles with large carbon content, which leads to low volumetric energy density of electrode. In this study, carbon-coated LiMnPO4 prepared by hydrothermal route was applied to the ball milling without carbon addition. The reduction of particle size of carbon-coated LiMnPO4 was achieved by the ball milling without destroying the surface carbon layer. The ball-milled LiMnPO4 particle revealed better cathodic performance than non-milled sample. This was attributed to shortening Li ion diffusion path, improvement of structural flexibility, and large surface area of electrode due to reduction of particle size. The ball milling is attested to be a promising method to improve cathodic performance of carbon-coated LiMnPO4. Masashi Kotobuki Copyright © 2013 Masashi Kotobuki. All rights reserved. Electrochemical Investigation on Adsorption of Fluconazole at Mild Steel/HCl Acid Interface as Corrosion Inhibitor Sun, 30 Dec 2012 15:35:03 +0000 The interfacial behavior of fluconazole on mild steel in 1 M HCl solution was studied by electrochemical methods, namely, polarization (Tafel Plot) and Electrochemical Impedance Spectroscopy (EIS). The surface morphology of mild steel in the presence and absence of fluconazole was studied by Atomic Force Microscopy (AFM). The results of the study showed that fluconazole reduced the corrosion rate in HCl acid solution by adsorbing on the surface of mild steel. Tafel results suggest that fluconazole behaves predominantly as an anodic inhibitor and shows greater inhibition efficiency (96%) at 0.30 mM. Thermodynamical parameters suggest that fluconazole is adsorbed on mild steel mainly by chemical mode. The EIS studies reveal the formation of a thin barrier film on mild steel surface. The AFM image of mild steel immersed in optimum concentration of fluconazole has confirmed the film formation on metal surface. T. Jebakumar Immanuel Edison and M. G. Sethuraman Copyright © 2013 T. Jebakumar Immanuel Edison and M. G. Sethuraman. All rights reserved. Comparison of Single-Walled and Multiwalled Carbon Nanotubes Durability as Pt Support in Gas Diffusion Electrodes Thu, 27 Dec 2012 11:55:09 +0000 Durability of single-walled (SWCNT) and multiwalled carbon nanotubes (MWCNT) as Pt supports was studied using two accelerated durability tests (ADTs), potential cycling and potentiostatic treatment. ADT of gas diffusion electrodes (GDEs) was once studied during the potential cycling. Pt surface area loss with increasing the potential cycling numbers for GDE using SWCNT was shown to be higher than that for GDE using MWCNT. In addition, equilibrium concentrations of dissolved Pt species from GDEs in 1.0 M H2SO4 were found to be increased with increasing the potential cycling numbers. Both findings suggest that Pt detachment from support surface plays an important role in Pt surface loss in proton exchange membrane fuel cell electrodes. ADT of GDEs was also studied following the potentiostatic treatments up to 24 h under the following conditions: argon purged, 1.0 M H2SO4, 60°C, and a constant potential of 0.9 V. The subsequent electrochemical characterization suggests that GDE that uses MWCNT/Pt is electrochemically more stable than other GDE using SWCNT/Pt. As a result of high corrosion resistance, GDE that uses MWCNT/Pt shows lower loss of Pt surface area and oxygen reduction reaction activity when used as fuel cell catalyst. The results also showed that potential cycling accelerates the rate of surface area loss. Mehdi Asgari and Elaheh Lohrasbi Copyright © 2013 Mehdi Asgari and Elaheh Lohrasbi. All rights reserved. High Performance PEM Fuel Cell with Low Platinum Loading at the Cathode Using Magnetron Sputter Deposition Tue, 25 Dec 2012 15:31:57 +0000 Platinum cluster formations have been investigated as a way to reduce the amount of Pt at the cathode of polymer electrolyte membrane fuel cells. One, two, and three layers of Pt (0.05 mg/cm2) sputtered directly on microporous layers of gas diffusion layers with and without interfacial carbon-Nafion layers and carbon-polytetrafluoroethylene (CPTFE) layers have been used as a cathode. Comparison with experimental results had showed that the best performance was obtained with three layers of Pt sputtered on carbon-Nafion containing 34.8 wt.% of Nafion and sputtered carbon-polytetrafluoroethylene containing 16.9 wt.% of polytetrafluoroethylene. High limiting current densities (>1.1 A/cm2) have been reached with cathode Pt loading as low as 0.05 mg/cm2. SEM imagery and cyclic voltammetry characterization have been performed to consolidate this study. High Pt utilization can be showed by this method. The factor influencing Pt utilisation in the oxygen reduction reaction is intrinsically related to Pt clusters formation and helps in enhancing the PEMFC performance with low Pt loading. Daouda Fofana, Sadesh Kumar Natarajan, Pierre Bénard, and Jean Hamelin Copyright © 2013 Daouda Fofana et al. All rights reserved.