Fuel Cell Science (Theory, Fundamentals, and Biocatalysis) || Mechanism of an Enhanced Oxygen Reduction Reaction at Platinum-Based Electrocatalysts: Identification and Quantification of Oxygen Species Adsorbed on Electrodes by X-Ray Photoelectron Spectroscopy
✍ Scribed by Wieckowski, Andrzej; Nørskov, Jens K.
- Publisher
- John Wiley & Sons, Inc.
- Year
- 2010
- Tongue
- English
- Weight
- 909 KB
- Edition
- 1
- Category
- Article
- ISBN
- 0470410299
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✦ Synopsis
In this chapter, a novel XPS study of the enhanced ORR mechanism of Pt-based alloy electrodes is presented in detail. The methodology employed for the identification and quantification of oxygen-containing species adsorbed on the Pt-based electrodes by XPS is described. The assignments of oxygen species are extensively discussed by utilizing a well-defined Pt(111) single-crystal electrode. Four types of oxygen species were distinguished, with binding energies at 529.6, 530.5, 531.1, and 532.6 eV; the first two were assigned to adsorbed atomic oxygen and hydroxyl, while the latter two were assigned to the bilayer water molecules. The coverage of each oxygen species was found to vary with the electrode potential and strongly depend on the Pt electrode types. The coverages of oxygen species in O 2 -saturated solution were also found to differ from those in N 2 -purged solution. Specifically, the coverage of atomic oxygen increased in the potential region where ORR took place. As compared to pure Pt, the enhanced ORR mechanism at the Pt-based alloy electrodes is discussed, on the basis of the coverage changes of atomic oxygen during ORR as well as apparent rate constants for the ORR evaluated by hydrodynamic voltammograms using channel flow double electrodes.