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Electrochemical Process (electrochemical + process)
Selected AbstractsStudy of Electrochemical Processes with Coupled Homogeneous Chemical Reaction in Differential Pulse Voltammetry at Spherical Electrodes and MicrohemispheresELECTROANALYSIS, Issue 16 2010Eduardo Laborda Abstract Homogeneous chemical reactions coupled to oxidation-reduction processes at electrode surfaces are very common in electrochemistry. In this paper we cope with the application of Differential Pulse Voltammetry at spherical electrodes and microhemispheres for the study of this kind of systems. Analytical expressions are deduced from which the influence of the different experimental variables is examined. Several diagnostic criteria for elucidation of the reaction mechanism from DPV peak parameters are given, as well as working curves for extraction of the kinetic rate constants of the chemical reaction. [source] Microwave Activation of Electrochemical Processes at Glassy Carbon and Boron-Doped Diamond ElectrodesELECTROANALYSIS, Issue 5-6 2005Kumar Sur, Ujjal Abstract Voltammetric experiments under intense microwave field conditions have been carried out at a carbon microfiber electrode, an array of carbon microfiber electrodes, and at a boron-doped diamond electrode. For the reversible one electron redox systems Fe(CN) and Ru(NH3) in aqueous KCl solution increased currents (up to 16 fold at a 33,,m diameter carbon microelectrode) and superheating (up to ca. 400,K at all types of electrodes) are observed. Electrodes with smaller diameter allow better signal enhancements to be achieved. From the missing effect of the supporting electrolyte concentration on the microwave enhanced currents, it can be concluded that effects observed at carbon electrodes (microwave absorbers) are due to the interaction of microwaves with the electrode material whereas for metal electrodes (microwave conductors) effects are dominated by the interaction of the microwaves with the aqueous dielectric. Short heat pulses can be applied by pulsing the microwave field and relatively fast temperature transients are observed for small electrodes. For the irreversible two electron oxidation of L -dopa in aqueous phosphate buffer, different types of effects are observed at glassy carbon and at boron-doped diamond. Arrays of carbon microfibers give the most reproducible and analytically useful current signal enhancements in the presence of microwaves. [source] Ni(II)cyclam Catalyzed Reduction of CO2 , Towards a Voltammetric Sensor for the Gas PhaseELECTROANALYSIS, Issue 18 2003P. Jacquinot Abstract The detection of CO2 in the gas phase is possible in presence of oxygen with an amalgamated Au-poly(tetrafluoroethylene) gas diffusion electrode and an internal electrolyte solution containing Ni(II)cyclam. For concentrations between 0.1 to 1% the electrochemical cell has a sensitivity of 3.58 mA %,1 and the detection limit is 500,ppm. In preliminary experiments at rotating disk electrodes the optimum pH-range was found to be between 3.5 to 6 and a selectivity ratio of the catalyst for CO2/H+ of 5,:,1 could be determined. The relationship between reduction current and the square root of the angular speed is linear, indicating that the electrochemical process is limited by diffusion of CO2. Tl and Pb are presented as alternative electrode materials at which the Ni(II)cyclam catalyzed reduction of CO2 can be observed. Problems arise from fouling effects at the sensing electrode and a non-linearity of the calibration plot at higher concentrations. [source] Spectroelectrochemical and Voltammetric Studies of L -DOPAELECTROANALYSIS, Issue 2 2003Xiaoqiang Liu Abstract The electrooxidation of L -dopa at GC electrode was studied by in situ UV-vis spectroelectrochemistry (SEC) and cyclic voltammetry. The mechanism of electrooxidation and some reaction parameters were obtained. The results showed that the whole electrooxidation reaction of L -dopa at glassy carbon (GC) electrode was an irreversible electrochemical process followed by a chemical reaction in neutral solution (EC mechanism). The spectroelectrochemical data were treated by the double logarithm method together with nonlinear regression, from which the formal potential E0=228,mV, the apparent electron-transfer number of the electrooxidation reaction ,n=0.376 (R=0.99, SD=0.26), the standard electrochemical rate constant k0=(3.93±0.12)×10,4,cm s,1 (SD=1.02×10,2), and the formation equilibrium constant of the following chemical reaction kc=(5.38±0.34)×10,1,s,1 (SD=1.02×10,2) were also obtained. [source] Thermomechanical and Thermal Contact Characteristics of Bismuth Telluride Films Electrodeposited on Carbon Nanotube ArraysADVANCED MATERIALS, Issue 42 2009Himanshu Mishra A scalable electrochemical process for addressing the thermomechanical compliance and contact resistance at metal/thermoelectric (M/TE) interfaces by integrating TE films with carbon nanotube (CNT) arrays is presented. Thermomechanical compliance and thermal contact characteristics of TE/CNT/M and TE/M contacts are compared. A process-flow for patterned electrodeposition of TE films on CNT arrays coated surfaces is also demonstrated. [source] Modeling an electrochemical process to remove Cr(VI) from rinse-water in a stirred reactorJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 4 2003Miriam G Rodríguez Abstract Experimental studies were developed in a batch reactor (16,dm3), to obtain the kinetic model of Cr(VI) removal by means of an electrochemical process. An overall kinetic model was obtained and experimentally validated in a continuous stirred electrochemical reactor (16,dm3) with synthetic and industrial wastewater. To develop the mathematical model of the continuous reactor in relation to the Cr(VI) and Fe(II) concentration in the solution, a classical mass balance procedure was performed. The Cr(VI) concentration in the electrochemically-treated waters was less than 0.5,mg,dm,3. In the electrochemical process the Cr(VI) reduction is caused by the Fe(II) released from the anode due to the electric current applied, by the Fe(II) released for the dissolution (corrosion) of the electrodes due to the acidic media, and by reduction at the cathode. During the process, reduction from Fe(III) to Fe(II) occurs. All of these different reactions cause a diminution in the quantity of sludge generated. Finally, it was found that due to the slow rate of reduction of Cr(VI) during the first part of the process it is necessary to develop a method of control to apply the process in a continuous industrial system. © 2003 Society of Chemical Industry [source] Electrochemical and optical properties of novel donor-acceptor thiophene-perylene-thiophene polymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2008Sermet Koyuncu Abstract In this study, donor-acceptor type thiophene-perylene-thiophene monomers were synthesized and polymerized by both oxidative polymerization using FeCl3 as catalyst and the electrochemical process. UV,vis, FTIR, 1H NMR, and elemental analysis techniques were used for structural characterization. Thermal behaviors of these compounds were determined by using TGA system. The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels and electrochemical and optical band gap values were calculated by using the results of cyclic voltammetry and UV,vis measurements, respectively. The number,average molecular weight (Mn), weight,average molecular weight (Mw), and polydispersity index (PDI) values of synthesized polymers were determined by size exclusion chromatography. Conductivity measurements of these polymers were carried out by electrometer by using a four-point probe technique. The conductivity was observed to be increased by iodine doping. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1974,1989, 2008 [source] Investigation of p-type macroporous silicon formationPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2005C. Lévy-Clément Abstract Nanopores and macropores can be formed electrochemically on p-type silicon depending on the silicon resistivity and composition of the electrolyte. In order to understand if the structural dimensionality of the porous p-type Si, either nanopore or macropore formation, depends on the electrochemical process at the Si/electrolyte interface, in situ pulsed surface photovoltage (SPV) and photoluminescence (PL) measurements have been undertaken. The SPV and PL studies have been made as a function of the applied current density as well as the electrolyte composition (aqueous or in presence of organic solvent) and the silicon doping density. Main results show that the Si surface is well passivated with preferential formation of ionic species and the Si band bending is around 100 mV, during porous Si formation. It varies slightly with the doping density, but is not affected by the composition of the electrolyte (HF/water and HF/organic solvent). This demonstrates that the chemistry of the electrolyte plays a major role in the formation of macroporous and nanoporous Si, but has still to be determined. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Copper Recovery from EDTA , Chelating , Copper Wastewater in a Fluidized BedTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2005Chien-Hsin Yang Abstract Copper recovery from ethylenediaminetetraacetic acid (EDTA)-chelating-Cu wastewater was conducted by means of electrochemical process using a Cu cathode and a PbO2 anode. In this study, the effects of operating parameters including current density, initial pH, and electrolytic-cell mode on the quality of copper deposit and current efficiency were studied. It was found that the key factors influencing deposit quality and current efficiency are current density and electrolytic cell mode as well as interactions between them. A better quality of copper deposit with high current efficiency can be obtained at lower current density (2.5 mA/cm2) in this fluidized packed-bed electrolytic cell. On a effectué la récupération de cuivre à partir d'eaux usées d'acide d'éthylènediamine-tétraacétique (EDTA)-Cu complexant par un procédé électrochimique utilisant une cathode de Cu et une anode de PbO2. On a étudié dans ce travail les effets des paramètres opératoires, dont la densité de courant, le pH initial et le mode de la cellule électrolytique, sur la qualité du dépôt de cuivre et le rendement du courant. On a trouvé que les facteurs clés influençant la qualité de déposition et le rendement du courant sont la densité de courant et le mode de la cellule électrolytique ainsi que les interactions mutuelles. Une meilleure qualité de dépôt de cuivre avec un haut rendement de courant peut être obtenu à une faible densité de courant (2,5 mA/cm2) dans cette cellule électrolytique à lit garni fluidisé. [source] Bleaching of indigo-dyed denim fabric by electrochemical formation of hypohalogenites in situCOLORATION TECHNOLOGY, Issue 2 2005Thomas Bechtold The use of hypochlorite, formed in situ by anodic oxidation of sodium chloride solution, for bleaching indigo-dyed denim has been studied at room temperature and at 50 °C. A direct relationship between the charge flow applied and the bleaching effect was observed. This enables consistent oxidative bleaching to be achieved by controlling the electrochemical process. The use of mixed anolytes containing small concentrations of bromide ions enhanced the bleaching effect considerably, even after lowering the temperature to room temperature. The molar concentration of bromide ions required was much lower than that of chloride in the anolyte. [source] Complete Elucidation of Electrode Reaction Mechanisms by Using Differential Pulse PolarographyELECTROANALYSIS, Issue 17-18 2010Miguel, Rodríguez Mellado Abstract By exploring the different parameters of the technique, it is shown that Differential Pulse Polarography (DPP) can be used for the elucidation of the reaction mechanisms of the electrochemical processes (with the evident exception of the product and intermediate identification). So, the type of transport towards or from the electrode can be identified from the dependence of the intensities with the pulse amplitude, the electrochemical reaction order with respect to the electroactive species from the shape of the polarogram, the type of rate-determining step from the dependence of the peak potentials on the pulse duration, the electrochemical reaction order with respect to other species, such as the H+ion, from the dependence of the peak potentials on their concentrations etc. [source] Recycling of nickel,metal hydride batteries.JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 9 2004II: Electrochemical deposition of cobalt, nickel Abstract A combination of hydrometallurgical and electrochemical processes has been developed for the separation and recovery of nickel and cobalt from cylindrical nickel,metal hydride rechargeable batteries. Leaching tests revealed that a 4 mol dm,3 hydrochloric acid solution at 95 °C was suitable to dissolve all metals from the battery after 3 h dissolution. The rare earths were separated from the leaching solution by solvent extraction with 25% bis(2-ethylhexyl)phosphoric acid (D2EHPA) in kerosene. The nickel and cobalt present in the aqueous phase were subjected to electrowinning. Galvanostatic tests on simulated aqueous solutions investigated the effect of current density, pH, and temperature with regard to current efficiency and deposit composition and morphology. The results indicated that achieving an NiCo composition with desirable properties was possible by varying the applied current density. Preferential cobalt deposition was observed at low current densities. Galvanostatic tests using solutions obtained from treatment of batteries revealed that the aqueous chloride phase, obtained from the extraction, was suitable for recovery of nickel and cobalt through simultaneous electrodeposition. Scanning electron micrography and X-ray diffraction analysis gave detailed information of the morphology and the crystallographic orientation of the obtained deposits. Copyright © 2004 Society of Chemical Industry [source] Initiating electropolymerization on graphene sheets in graphite oxide structureJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2010Ali Eftekhari Abstract Because of its special chemical composition, graphite oxide has peculiar influences on electrochemical processes. The existence of various functional groups significantly affects electropolymerization processes and the formation of conductive polymers. Electrochemical synthesis of polyaniline (as a prototype of conductive polymers) on a paste-based substrate of graphite oxide was investigated. In this case, the electropolymerization is significantly different from conventional cases, and the polymer is generated just during the first potential cycle. This can be attributed to the fact that graphite oxide can assist the monomer oxidation. Alternatively, electropolymerization was successfully performed inside the graphite oxide layers via electrochemical treatment of aniline-intercalated graphite oxide in the supporting electrolyte. Although these phenomena are related to the chemical composition of graphite oxide, the graphite prepared by the reduction of graphite oxide also displayed some advantages for the electropolymerization (over natural graphite). There is an emphasis on the morphological investigations throughout this study, because novel morphologies were observed in the system under investigation. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2204,2213, 2010 [source] | |||||||||||||