An overview of the electrochemical reduction of oxygen at carbon-based modified electrodes

Journal of the Iranian Chemical Society (Impact Factor: 1.47). 2:1-25. DOI: 10.1007/BF03245775

ABSTRACT We present an overview of the electrochemical reduction of oxygen in water, focussing on carbon-based and modified carbon electrodes. This process is of importance for gas sensing, in fuel cells and in the electrosynthesis of hydrogen peroxide.

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    ABSTRACT: The reduction of oxygen in alkaline solution has been studied on highly oriented pyrolytic graphite (HOPG) electrodes modified with various quinones using a rotating disk electrode (RDE). The electrode surface was modified by adsorption of quinones from a 0.1 M KOH solution. The oxygen reduction activity of these electrodes was considerably higher than that for unmodified HOPG and characteristic current maxima for oxygen reduction was observed. All quinones studied catalysed the two-electron reduction of oxygen to hydrogen peroxide. The peak potentials for oxygen reduction were in good correlation with the redox potentials of the quinones that were found from the cyclic voltammograms in oxygen-free solutions. The results obtained give further evidence that oxygen reduction is catalysed by the semiquinone radical and that the redox potential of the quinone is the most important factor determining its electrocatalytic activity for oxygen reduction.
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    ABSTRACT: To develop the high-efficiency carbon alloy catalysts with significant interaction of C–N, the synergy effects of the polypyrrole/single-walled carbon nanotube (PPy/SWCNT) composites have been studied for the oxygen reduction reaction (ORR) in an alkaline solution. The synergy effects between PPy and SWCNT have been found in the synthesized PPy/SWCNT composites by the characterization using FE-SEM, Raman spectroscopy, XRD, TGA, electrical conductivity, and the electrochemical measurements for the surface area and the electrochemical activities of sites: electron transfer rate, differential capacitance and chemisorbed H-stripping voltammetry. The synergy effects have significantly affected the electrochemical properties of the PPy/SWCNT composites and the electrocatalytic potential at the active sites. The PPy/SWCNT composites synthesized using the electrochemical polymerization method with an identified PPy:SWCNT weight ratio of 1:2 show the best performance of the ORR. For the electrode process on the PPy/SWCNT composites, a mixture of two-electron and four-electron processes occurred. It was found that the synergy effects in the PPy/SWCNT composite electrodes synthesized using the electrochemical polymerization method with a thin net-like PPy film were stronger than those using the chemical polymerization method with a thick shell-like PPy film and played an important role in the ORR electrode kinetics.
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    ABSTRACT: A new sandwich structure nanocomposite of Ag nanoparticles supported on MnO2 modified multiwall carbon nanotubes is synthesized and used for fabricating nonenzymatic H2O2 sensor. The morphology and composition of the nanocomposites are characterized by transmission electron microscope, energy-dispersive X-ray spectrum, X-ray diffraction and Fourier transform infrared spectrum. Electrochemical investigation indicates that the nanocomposites possess an excellent performance toward H2O2. In deaerated buffer solutions, the sensor could detect H2O2 in a linear range of 5.0 μM to 10.4 mM with a correlation coefficient of 0.9993, a sensitivity of 82.5 μA mM−1 cm−2, a detection limit of 1.7 μM at a signal-to-noise ratio of 3, and a response time of 2 s. Additionally, the sensor exhibits long-term stability, good reproducibility and anti-interference.
    Electrochimica Acta. 90:35–43.

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May 21, 2014