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Diffusion Electrode (diffusion + electrode)

Distribution by Scientific Domains
Chemistry100%

Kinds of Diffusion Electrode

  • gas diffusion electrode
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    Selected Abstracts

    Gas Diffusion Electrodes for Use in an Amperometric Enzyme Biosensor

    ELECTROANALYSIS, Issue 21 2008
    Martin Hämmerle
    Abstract The preparation of gas diffusion electrodes and their use in an amperometric enzyme biosensor for the direct detection of a gaseous analyte is described. The gas diffusion electrodes are prepared by covering a PTFE membrane (thickness 250,,m, pore size 2,,m, porosity 35%) with gold, platinum, or a graphite/PTFE mixture. Gold and platinum are deposited by e-beam sputtering, whereas the graphite/PTFE layer is prepared by vacuum filtration of a respective aqueous suspension. These gas diffusion electrodes are exemplarily implemented as working electrodes in an amperometric biosensor for gaseous formaldehyde containing NAD-dependent formaldehyde dehydrogenase from P. putida [EC. 1.2.1.46] as enzyme and 1,2-naphthoquinone-4-sulfonic acid as electrochemical mediator. The resulting sensors are compared with regard to background current, signal noise, linear range, sensitivity, and detection limit. In this respect, sensors with gold or graphite/PTFE covered membranes outclass ones with platinum for this particular analyte and sensor configuration. [source]

    Ni(II)cyclam Catalyzed Reduction of CO2 , Towards a Voltammetric Sensor for the Gas Phase

    ELECTROANALYSIS, Issue 18 2003
    P. 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]

    Comparison of ethanol and methanol crossover through different MEA components and structures by cyclic voltammetry

    ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2009
    J. Ling
    Abstract The crossover rate of ethanol or methanol through membrane electrode assembly (MEA) and MEA components was studied quantitatively at 25 and 60 °C by cyclic voltammetry method. The results obtained in this work show that cyclic voltammetry is a powerful technique to assess the crossover phenomenon through MEA components and structures. In all cases, the ethanol crossover rates are lower than those of methanol. The ethanol and methanol crossover rates depend upon time and temperature. For an initial concentration of 1 M of ethanol or methanol, the crossover rate increases to a maximum after the first hour of the cell operation and then decreases gradually to a certain concentration after the third hour. At 60 °C, the maximum concentration of ethanol crossover rate is lower than that obtained at 25 °C. The crossover rate of ethanol or methanol through MEA is lower than through the components alone (pressed or nonpressed membranes or gas diffusion electrode). Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

    Gas Diffusion Electrodes for Use in an Amperometric Enzyme Biosensor

    ELECTROANALYSIS, Issue 21 2008
    Martin Hämmerle
    Abstract The preparation of gas diffusion electrodes and their use in an amperometric enzyme biosensor for the direct detection of a gaseous analyte is described. The gas diffusion electrodes are prepared by covering a PTFE membrane (thickness 250,,m, pore size 2,,m, porosity 35%) with gold, platinum, or a graphite/PTFE mixture. Gold and platinum are deposited by e-beam sputtering, whereas the graphite/PTFE layer is prepared by vacuum filtration of a respective aqueous suspension. These gas diffusion electrodes are exemplarily implemented as working electrodes in an amperometric biosensor for gaseous formaldehyde containing NAD-dependent formaldehyde dehydrogenase from P. putida [EC. 1.2.1.46] as enzyme and 1,2-naphthoquinone-4-sulfonic acid as electrochemical mediator. The resulting sensors are compared with regard to background current, signal noise, linear range, sensitivity, and detection limit. In this respect, sensors with gold or graphite/PTFE covered membranes outclass ones with platinum for this particular analyte and sensor configuration. [source]

    Electrochemical Reduction of Oxygen on Carbon Supported Pt and Pt/Ru Fuel Cell Electrodes in Alkaline Solutions

    FUEL CELLS, Issue 4 2003
    E.H. Yu
    Abstract A study of O2 reduction in 1 M NaOH solution at gas diffusion electrodes made from carbon supported Pt and Pt/Ru catalysts is reported. Two Tafel regions were observed for both the Pt and Pt/Ru electrodes. Although the same mechanism was suggested for oxygen reduction on both Pt and Pt/Ru catalysts, the O2 reduction activity was lower on Ru. Electrochemical Impedance Spectroscopy (EIS) analysis was carried out at different potentials and showed the significant contribution of diffusion on the reaction process and kinetics. The effect of methanol on O2 reduction was investigated in solutions containing various concentrations of methanol. The electrode performance deteriorated with increasing methanol concentration because of a mixed cathode potential. The methanol tolerance, i. e., the methanol concentration which polarises the O2 reduction reaction for O2 reduction, at the Pt/C electrode with a Pt loading of 1.2 mg cm,2 is 0.2 M methanol in 1 M NaOH. [source]