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    A Study of Ascorbic Acid Electro-Oxidation Process on Silver and Silver Selenide Electrodes

    , Ph.D. Dissertation Sharif University of Technology Majari Kasmaee, Laleh (Author) ; Gobal, Fereydoon (Supervisor)
    Abstract
    Electrocatalytic oxidation of L-ascorbic acid (L-AA) on silver electrode in alkaline solutions was studied employing cyclic voltammetry, chronoamperometry and impedance spectroscopy techniques. In comparison to Pt, the onset potential for L-AA electro-oxidation process on Ag, in a solution containg 0.02 M L-AA and 0.5 M NaOH, was 0.1 V more negative. Also, L-AA oxidation current increased more than 900% at -0.26 V/SCE. According to voltammety and impedance spectropy findings, although hydroxide anion presence was vital for L-AA oxidation to occur, at potentials more positive than -0.2 V/SCE, hydroxide ion tends to inhibit the oxidation process. Studies on the L-AA oxidation process on Ag in... 

    Experimental and Theoretical investigation of Electro-oxidation of C1 Compounds on Nickel and Copper Surfaces

    , M.Sc. Thesis Sharif University of Technology Zeinaghaji, Mohammad (Author) ; Gobal, Fereydoon (Supervisor)
    Abstract
    A study of the electro-oxidation and surface reactions of C1 compounds on Ni and Cu electrodes, Ni(111) and Cu (111) has been performed by methods of cyclic voltammetry, BOC-MP and DFT. The diffusion coefficients and activation energies of the electro-oxidation of methanol and formaldehyde in alkaline solution on Ni electrode have been derived. Values around 2.27×10-6 cm2s-1, 1.98×10-5cm2s-1, 12.15 Kcal mol-1 and 11.65 Kcal mol-1 have been obtained respectively. In theoretical study , the elimination of hydrogen from CH3 and CH2 groups has been proposed as a mechanism in surface reactions of methanol and formaldehyde on Ni(111) ... 

    The Poisoning Effect of Sulfur-Containing Compounds on the Elelctro-Oxidation of Methanol and Ethanol on Ni and Cu Electrodes

    , M.Sc. Thesis Sharif University of Technology Valadbeigi, Younes (Author) ; Gobal, Fereydon (Supervisor)
    Abstract
    In this study a systematic effort was made to investigate the poisoning effect of sulfur-containing materials on the electro- oxidation of methanol and ethanol on Ni and Cu electrodes in alkaline solutions by the methods of cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. Activation energy of methanol electro-oxidation in the absence of Na2S was obtained 30.7 kJ/mol by cyclic voltammetric at different temperatures, and its values increased by increase in Na2S concentrations to 97kJ/mol. Na2S adsorption isotherms corresponded with Langmuire isotherm, equilibrium constants of adsorption – desorption and adsorption enthalpy (ΔHads= -62kJ/mol) were calculated for... 

    A Comparative Study of the Redox Processes of Iodide Ion on Pt, C and Carbon-Polyorthoaminophenol

    , M.Sc. Thesis Sharif University of Technology Safar Kolachaee, Leila (Author) ; Gobal, Feridon (Supervisor)
    Abstract
    In this study a systematic effort was made to study and compare electrochemical oxidation behavior of iodide on Pt, carbon and carbon supported polyorthoaminophenol film electrodes. All of the electrochemical experiments were performed in acidic, basic and nuteral aqueous solutions and the applied electrochemical techniques included Chronoamperometry (CA) and Cyclic voltammetry (CV). Effects of concentration and scan rate of potential on the cyclic voltammetry of KI was studied at the previously mentioned electrodes. Current-time and log current-potential curves were analyezed quantitavely in order to determine kinetic parameters. Carbon supported polyorthoaminophenol electrode was prepared... 

    Preparation of Nanocomposites Consisting of Nickel Oxide Nanostructures Grown on Hollow Carbon Nanospheres and Evaluation of their Ability for Electrooxidation of Hydrazine Hydrate

    , M.Sc. Thesis Sharif University of Technology Taghaddosi, Sanaz (Author) ; Shahrokhian Dehkordi, Saeed (Supervisor)
    Abstract
    In the present work, nanocomposites consisting of nickel oxide nanostructures and a hollow carbon substrate were used to modify a glassy carbon electrode's surface for the electrooxidation of hydrazine hydrate. For this purpose, hollow carbon nanospheres were first synthesized using aniline and pyrrole copolymerization process without any template needing. The hollow carbon nanospheres prepared by this method have outstanding features such as high specific surface area and good stability. On the other hand, they did not require toxic and environmentally harmful solvents to remove the template. In this study, after preparing hollow carbon nanospheres as a suitable substrate, different... 

    Modification of Electrode Substrates Using Nanocomposites Including Carbon Nanomaterials and Multimetallic Nanoparticles for Electrocatalysis of some Fuel Cells Reactions

    , Ph.D. Dissertation Sharif University of Technology Rezaee, Sharifeh (Author) ; Shahrokhian, Saeed (Supervisor)
    Abstract
    In this research, nanocomposite containing reduced graphene oxide nanosheets (RGO) and trimetallic three-dimensional (3D) Pt-Pd-Co porous nanostructures was fabricated by galvanic replacement technique. First, GO suspension was drop-casted on the electrode surface, then GO film reduction was carried out by cycling the potential in negative direction to form the RGO on GCE (RGO/GCE). Then, electrodeposition of the cobalt nanoparticles (CoNPs) as sacrificial seeds was performed onto the RGO/GCE by using cyclic voltammetry. Afterward, Pt-Pd-Co 3D porous nanostructures fabrication occurs through galvanic replacement method based on a spontaneous redox process between CoNPs and solution... 

    Polysulfide poisoning of Ag electrocatalyst during L-ascorbate ion electro-oxidation in alkaline solution

    , Article Cuihua Xuebao/Chinese Journal of Catalysis ; Volume 33, Issue 2 , 2012 , Pages 267-274 ; 02539837 (ISSN) Gobal, F ; Majari Kasmaee, L ; Sharif University of Technology
    Abstract
    L-Ascorbate anion electro-oxidation on a silver electrode in hydroxide solution in the absence and presence of sodium polysulfide of concentrations from 1 × 10 -5 to 4.5 × 10 -4 mol/L was studied using cyclic voltammetry and electrochemical impedance spectroscopy. Both hydroxide and polysulfide ions inhibited L-ascorbate ion oxidation, with the poisoning effect of polysulfide ion being more pronounced in the potential range of -0.3 to -0.2 V/SCE. The time constants for L-ascorbate ion oxidation in the absence and presence of polysulfide were, 10 -3 to 1 × 10 -2 s and 1 × 10 -4 to 1 × 10 -2 s, respectively depending on the potential used for the impedance analysis. Based on the cyclic... 

    On the significance of hydroxide ion in the electro-oxidation of methanol on Ni

    , Article Journal of Electroanalytical Chemistry ; Volume 650, Issue 2 , January , 2011 , Pages 219-225 ; 15726657 (ISSN) Gobal, F ; Valadbeigi, Y ; Kasmaee, L. M ; Sharif University of Technology
    2011
    Abstract
    Electro-oxidation of methanol on Ni in NaOH solutions with the alkali concentration in the range of 0.05-0.5 M and in the presence of 0.5 M Na 2SO4 supporting electrolyte is studied. All the mentioned species compete for adsorption on Ni and OH- is essential for the electro-oxidation process. The electro-oxidation seems to proceed through the electro-chemical reactions of adsorbed methanol and hydroxide species and the removal of the resulting intermediate by adsorbed hydroxyl groups. The mechanism is consistent with the cyclic voltammetry and impedance spectroscopy results and can semi-quantitatively account for the appearance of capacitive, inductive and negative resistance loops as well... 

    Silver selenide as a potential electro-catalyst for l-ascorbic acid electro-oxidation in alkaline solution

    , Article Electrocatalysis ; Volume 2, Issue 4 , December , 2011 , Pages 331-336 ; 18682529 (ISSN) Gobal, F ; Majari Kasmaee, L ; Sharif University of Technology
    Abstract
    Cathodically deposited Ag 2Se, to form a 1-μm-thick film, characterized by energy dispersive X-ray analysis and scanning electron microscopy, showed high electro-catalytic activity for l-ascorbic acid oxidation in alkaline solution. The onset of the process was about 80 mV cathodic of that previously observed on Ag under the same conditions and far superior over glassy carbon and Pt. The values of the exchange current density, standard heterogeneous rate constant, and transfer coefficient of the reaction were 1. 65 × 10 -4 A cm -2, 4. 35 × 10 -7 cm s -1, and 0. 60, respectively. Diffusion coefficient of l-ascorbate di-anion was also measured and was around 7. 00 × 10 -6 cm 2 s -1  

    Electrocatalytic Oxidation of 1-Propanol and 2-Propanol on Electro-active Films Derived from Ni II-(N,N′-bis(2-Hydroxy, 3-Methoxy Benzaldehyde)-1,2-Propandiimine) Modified Glassy Carbon Electrode

    , Article Electrocatalysis ; Volume 2, Issue 3 , Volume 2, Issue 3 , 2011 , Pages 163-171 ; 18682529 (ISSN) Jafarian, M ; Rashvand avei, M ; Gobal, F ; Rayati, S ; Mahjani, M. G ; Sharif University of Technology
    Abstract
    Complexes of Ni II-(N,N′-bis(2-hydroxy, 3-methoxy benzaldehyde)-1,2-propandiimine) can be electro-polymerized onto GC electrode in an alkaline solution to give an electro-active film strongly adhered on the electrode surface. In alkaline solution, this poly-(Ni II{sal-1,2-pn(3-OMe) 2})/GC film shows the typical voltammetric response of a surface-immobilized redox couple, as can be anticipated for the Ni 2+/Ni 3+ transitions into the film. In addition, the film exhibits a potent and persistent electro-catalytic activity towards the oxidation of 1- and 2-propanol. In CV studies, in the presence of these alcohols, poly-(Ni II{sal-1,2-pn(3-OMe) 2})/GC electrode shows a new oxidation peak for the... 

    Synergistic effect of cobalt and copper on a nickel-based modified graphite electrode during methanol electro-oxidation in NaOH solution

    , Article Cuihua Xuebao/Chinese Journal of Catalysis ; Volume 36, Issue 11 , 2015 , Pages 1867-1874 ; 02539837 (ISSN) Rostami, T ; Jafarian, M ; Miandari, S ; Mahjani, M. G ; Gobal, F ; Sharif University of Technology
    Abstract
    The electrocatalytic oxidation of methanol was studied over Ni, Co and Cu binary or ternary alloys on graphite electrodes in a NaOH solution (0.1 mol/L). The catalysts were prepared by cycling the graphite electrode in solutions containing Ni, Cu and Co ions at cathodic potentials. The synergistic effects and catalytic activity of the modified electrodes were investigated by cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). It was found that, in the presence of methanol, the modified Ni-based ternary alloy electrode (G/NiCuCo) exhibited a significantly higher response for methanol oxidation compared to the other samples. The anodic peak... 

    A preliminary study of the electro-oxidation of l-ascorbic acid on polycrystalline silver in alkaline solution

    , Article Journal of Power Sources ; Volume 195, Issue 1 , 2010 , Pages 165-169 ; 03787753 (ISSN) Majari Kasmaee, L ; Gobal, F ; Sharif University of Technology
    2010
    Abstract
    Electrochemical oxidation of l-ascorbic acid on polycrystalline silver in alkaline aqueous solutions is studied by cyclic voltammetry (CV), chronoamperometry (CA) and impedance spectroscopy (IS). The anodic electro-oxidation starts at -500 mV versus SCE and shows continued anodic oxidation in the cathodic half cycle in the CV regime signifying slowly oxidizing adsorbates. Diffusion coefficient of ascorbate ion measured under both voltammetric regimes is around 1.4 × 10-5 cm2 s-1. Impedance spectroscopy measures the capacitances associated with double layer and adsorption around 50 μF cm-2 and 4 mF cm-2 as well as the adsorption and decomposition resistances (rates). © 2009 Elsevier B.V. All... 

    Nanocomposite with promoted electrocatalytic behavior based on bimetallic pd-ni nanoparticles, manganese dioxide, and reduced graphene oxide for efficient electrooxidation of ethanol

    , Article Journal of Physical Chemistry C ; Volume 122, Issue 18 , 2018 , Pages 9783-9794 ; 19327447 (ISSN) Rezaee, S ; Shahrokhian, S ; Amini, M. K ; Sharif University of Technology
    American Chemical Society  2018
    Abstract
    In this work, a nanocomposite containing manganese dioxide (MnO2) modified reduced graphene oxide (rGO) supported bimetallic palladium-nickel (Pd-Ni) catalyst is prepared by electrodeposition method. The nanocomposite modifier film is prepared by forming a thin layer of graphene oxide (GO) via drop-casting of GO nanosheet dispersion on glassy carbon electrode (GCE), followed by electrochemical reduction of the film to provide rGO/GCE. Then, a two-step potential procedure is applied to deposit MnO2 nanoparticles on rGO/GCE. At the optimum deposition conditions, MnO2 nanoparticles with a thickness of 30-50 nm homogeneously covered the rGO surface (MnO2/rGO/GCE). Finally, the bimetallic Pd-Ni... 

    Application of carbon-paste electrode modified with iron phthalocyanine for voltammetric determination of epinephrine in the presence of ascorbic acid and uric acid

    , Article Sensors and Actuators, B: Chemical ; Volume 137, Issue 2 , 2009 , Pages 669-675 ; 09254005 (ISSN) Shahrokhian, S ; Ghalkhani, M ; Amini, M. K ; Sharif University of Technology
    2009
    Abstract
    A carbon-paste electrode (CPE) modified with iron(II) phthalocyanine was used for the sensitive voltammetric determination of epinephrine (EN). The electrochemical response characteristics of the modified electrode toward EN, ascorbic acid (AA) and uric acid (UA) were investigated by cyclic and differential pulse voltammetry (CV and DPV). The results show an efficient catalytic activity of the electrode for the electro-oxidation of EN, which leads to improvement of reversibility of the electrode response and lowering its overpotential by more than 100 mV. The effect of pH and potential sweep rate on the mechanism of the electrode process was investigated. The modified electrode exhibits an... 

    Electrochemical impedance studies of methanol oxidation on GC/Ni and GC/NiCu electrode

    , Article International Journal of Hydrogen Energy ; Volume 34, Issue 2 , 2009 , Pages 859-869 ; 03603199 (ISSN) Danaee, I ; Jafarian, M ; Forouzandeh, F ; Gobal, F ; Mahjani, M. G ; Sharif University of Technology
    2009
    Abstract
    The electro-oxidation of methanol on nickel and nickel-copper alloy modified glassy carbon electrodes (GC/Ni and GC/NiCu) in a 1 M NaOH solution at different concentrations of methanol was studied by the method of ac-impedance spectroscopy. Two semicircles in the first quadrant of a Nyquist diagram were observed for electro-oxidation of methanol on GC/Ni corresponding to charge transfer resistance and adsorption of intermediates. Electro-oxidation of methanol on GC/NiCu shows negative resistance in impedance plots as signified by semi-circles terminating in the second quadrant. The impedance behavior shows different patterns at different applied anodic potential. The influence of the... 

    3D ternary Ni: XCo2- xP/C nanoflower/nanourchin arrays grown on HCNs: A highly efficient bi-functional electrocatalyst for boosting hydrogen production via the urea electro-oxidation reaction

    , Article Nanoscale ; Volume 12, Issue 30 , 2020 , Pages 16123-16135 Rezaee, S ; Shahrokhian, S ; Sharif University of Technology
    Royal Society of Chemistry  2020
    Abstract
    Over the last few years, substantial efforts have been made to develop earth-abundant bi-functional catalysts for urea oxidation and energy-saving electrolytic hydrogen production due to their low cost and the potential to replace traditional noble-metal-based catalysts. Nevertheless, finding a straightforward and effective route to prepare efficient catalysts with unique structural features and optimal supports still is a big challenge. Among the various candidates, metal-organic framework (MOF)-derived materials show great advantages as new kinds of active non-precious catalysts. On the other hand, the controllable integration of MOFs and carbon-based nanomaterials leads to further... 

    Differential pulse voltammetric determination of N-acetylcysteine by the electrocatalytic oxidation at the surface of carbon nanotube-paste electrode modified with cobalt salophen complexes

    , Article Sensors and Actuators, B: Chemical ; Volume 133, Issue 2 , 12 August , 2008 , Pages 599-606 ; 09254005 (ISSN) Shahrokhian, S ; Kamalzadeh, Z ; Bezaatpour, A ; Boghaei, D. M ; Sharif University of Technology
    2008
    Abstract
    The preparation and electrochemical performance of the carbon nanotube-paste electrode modified with salophen complexes of cobalt(III) perchlorate, with various substituents on the salophen ligand, as well as their electrocatalytic activity toward the oxidation of N-acetylcysteine (NAC) is investigated. Several Schiff base complexes containing various nucleophilic and electrophilic functional groups were prepared, and their electrochemical characteristics for the electro-oxidation of NAC were evaluated using cyclic and differential pulse voltammetry (CV and DPV). The results revealed, the modified electrodes show an efficient and selective electrocatalytic activity toward the anodic... 

    Electro-oxidation of methanol on copper in alkaline solution

    , Article Electrochimica Acta ; Volume 49, Issue 27 , 2004 , Pages 4999-5006 ; 00134686 (ISSN) Heli, H ; Jafarian, M ; Mahjani, M. G ; Gobal, F ; Sharif University of Technology
    Elsevier Ltd  2004
    Abstract
    The electro-oxidation of methanol on copper in alkaline solutions has been studied by the methods of cyclic voltammetry, quasi-steady state polarization and chronoamperometry. It has been found that in the course of an anodic potential sweep the electro-oxidation of methanol follows the formation of CuIII and is catalysed by this species through a mediated electron transfer mechanism. The reaction also continues in the early stages of the reversed cycle until it is stopped by the prohibitively negative potentials. The process is diffusion controlled and the current-time responses follow Cottrellian behavior. The rate constants, turnover frequency, anodic transfer coefficient and the apparent... 

    A study of the electro-catalytic oxidation of methanol on a cobalt hydroxide modified glassy carbon electrode

    , Article Electrochimica Acta ; Volume 48, Issue 23 , 2003 , Pages 3423-3429 ; 00134686 (ISSN) Jafarian, M ; Mahjani, M. G ; Heli, H ; Gobal, F ; Khajehsharifi, H ; Hamedi, M. H ; Sharif University of Technology
    2003
    Abstract
    Cobalt hydroxide modified glassy carbon electrodes (CHM/GC) prepared by the anodic deposition in presence of tartrate ions have been used for the electro-catalytic oxidation of methanol in alkaline solutions where the methods of cyclic voltammetery (CV), chronoamperometry (CA) and impedance spectroscopy (IS) have been employed. In CV studies, in the presence of methanol the peak current of the oxidation of cobalt hydroxide increase is followed by a decrease in the corresponding cathodic current. This suggests that the oxidation of methanol is being catalysed through the mediated electron transfer across the cobalt hydroxide layer comprising of cobalt ions of various valence states. A... 

    Facile electrochemical detection of morpholine in boiler water with carbon nanostructures: a comparative study of graphene and carbon nanotubes

    , Article Bulletin of Materials Science ; Volume 45, Issue 2 , 2022 ; 02504707 (ISSN) de Oliveira, S. M ; dos Santos Castro Assis, K. L ; Paiva, V. M ; Hashempour, M ; Bestetti, M ; de Araújo, J. R ; D’Elia, E ; Sharif University of Technology
    Springer  2022
    Abstract
    Two electrochemical sensors based on modified glassy carbon electrodes with carbon nanostructures as graphene (GCE–EG) and carbon nanotubes (GCE–CNT) were evaluated for morpholine analysis. The carbon nanostructures were obtained and characterized using X-ray photoelectron spectroscopy, Raman spectroscopy, X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy and cyclic voltammetry. All spectroscopic and microscopic techniques confirmed the procurement of graphene and CNT. The electrochemical studies proved the efficient behaviour of both electrodes GCE–EG and GCE–CNT in sensing and detection of morpholine via differential pulse voltammetry....