Electrode kinetics oxygen reduction

The mechanism of the oxygen reduction reaction is by no means as fully understood as the h.e.r., and a major experimental difficulty is that in acid solutions (pH = 0) E02/H20 = 1 23, which means that oxygen will start to be reduced at potentials at which most metals anodically dissolve. For this reason accurate data on kinetics is available only for the platinum metals. In the case of an iridium electrode at which oxygen reduction is relatively rapid, a number of reaction sequences have been proposed, of which the most acceptable appear to be the following ... 

The overpotentials for oxygen reduction and evolution on carbon-based bifunctional air electrodes for rechargeable Zn/air batteries are reduced by utilizing metal oxide electrocatalysts. Besides enhancing the electrochemical kinetics of the oxygen reactions, the electrocatalysts serve to reduce the overpotential to minimize... 

In this section, we summarize the kinetic behavior of the oxygen reduction reaction (ORR), mainly on platinum electrodes since this metal is the most active electrocatalyst for this reaction in an acidic medium. The discussion will, however, be restricted to the characteristics of this reaction in DMFCs because of the possible presence in the cathode compartment of methanol, which can cross over the proton exchange membrane. 

Parthasarathy A, Srinivasan S, Appleby AJ, et al. 1992a. Temperature dependence of the electrode kinetics of oxygen reduction at the platinum/Nafion interface—A microelectrode investigation. J Electrochem Soc 139 2530-2537. 

Damjanovic A, Bmsic V. 1967. Electrode kinetics of oxygen reduction on oxide-free platinum electrodes. Electrochim Acta 12 615-628. 

Lawson DR, Whiteley LD, Martin CR. 1988. Oxygen reduction at Nafion film-coated platinum electrodes Transport and kinetics. J Electrochem Soc 135 2247-2253. 

Sepa DB, Vojnovic MV, Damjanovic A. 1981. Reaction intermediates as a controlling factor in the kinetics and mechanism of oxygen reduction at platinum electrodes. Electrochim Acta 26 781-793. 

Solid alkaline membrane fuel cells (SAMECs) can be a good alternative to PEMFCs. The activation of the oxidation of alcohols and reduction of oxygen occurring in fuel cells is easier in alkaline media than in acid media [Wang et al., 2003 Yang, 2004]. Therefore, less Pt or even non-noble metals can be used owing to the improved electrode kinetics. Eor example, Ag/C catalytic powder can be used as an efficient cathode material [Demarconnay et al., 2004 Lamy et al., 2006]. It has also... 

Markovic N, GasteigerH, Ross PN. 1997a. Kinetics of oxygen reduction on ViQikl) electrodes Implications for the crystalhte size effect with supported Pt electrocatalysts. J Electrochem Soc 144 1591-1597. 

Hsueh KL, Gonzalez ER, Srinivasan S. 1983. Electrolyte effects on oxygen reduction kinetics at platinum—A rotating-ring disk electrode analysis. Electrochim Acta 28 691-697. 

Oxygen reduction can be accelerated by an application of electrodes with high surface area, e.g. the porous electrodes [9, 13]. The porous electrodes usually consist of catalysts, hydrophobic agent (polytetrafluoroethylene-PTFE) and conductive additive. Electrode kinetics on the porous electrodes is complicated by the mass and charge transfer in the pores and is called the macrokinetics of electrode processes . 

The impedance polarization performance of LSM electrode is closely related to the mechanism and kinetics of the oxygen reduction reactions. 02 reduction at SOFC cathodes is the most heavily studied subject, and this subject is sufficiently broad and complex to warrant its own review. Interested readers should consult the recent excellent articles by Adler [1] and Fleig [55], Here, only the polarization performance and its influencing factors are discussed. 

Lawson, D. R., Whiteley, L. D., Martin, C. R., Szentimay, M. N. and Song, J. I. 1988. Oxygen reduction at Nation film-coated platinum electrodes Transport and kinetics. Journal of the Electrochemical Society 135 2247-2253. 

Co-limited kinetics with a significant utilization region. As with platinum, the model predicts that the chemical portion of the reaction will be co-limited by molecular dissociation and transport. Values of k calculated from the model for the analyzed conditions vary from 0.4 to 20 gvc depending on Pq2 temperature, and electrode surface area, with typical values in the 3—5 gm range. This result indicates that a significant portion of the electrode surface is active for oxygen reduction, which explains Takeda s (and other s) observation that the performance of LSG electrodes on YSZ improves with thickness up to a... 

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