Oxygen reduction reaction at three-phase interfaces.
The kinetics of the oxygen reduction reaction (ORR) is studied at metal-supporting electrolyte-Nafion three-phase interfaces. We first demonstrate that the sulfonate anions of Nafion are specifically adsorbed on a wide range of surfaces ranging from Pt(hkl) single-crystal surfaces, Pt-poly, Pt-skin [produced on a Pt{sub 3}Ni(111) surface by annealing in ultrahigh vacuum, UHV] to high-surface-area nanostructured thin-film (NSTF) catalysts. The surface coverage by sulfonate and the strength of the Pt-sulfonate interaction are strongly dependent on the geometry and the nature of the Pt surface atoms. Also, they are found to behave analogous to (bi)sulfate anion-specific adsorption on these surfaces, where for the Pt(hkl) surfaces, the trend is Pt(111) > Pt(110) > Pt(100) and for the Pt-skin surface on Pt{sub 3}Ni(111), the interaction strength is found to be Pt-skin < Pt(111). We also found that irrespective of the surface orientation and/or the electronic properties of the surface atoms, the ORR is always inhibited by the presence of ionomers at the electrode surface, confirming that Nafion is not a non-adsorbing electrolyte. Finally, the knowledge gained from studying well-defined Pt(hkl) surfaces is applied to propose that deactivation of the ORR on Nafion-covered high-surface-area catalysts is also controlled by specific adsorption of sulfonate anions.
- Research Organization:
- Argonne National Laboratory (ANL)
- Sponsoring Organization:
- SC
- DOE Contract Number:
- AC02-06CH11357
- OSTI ID:
- 1000682
- Report Number(s):
- ANL/MSD/JA-68681
- Journal Information:
- ChemPhysChem, Journal Name: ChemPhysChem Journal Issue: 13 ; Sep. 10, 2010 Vol. 11; ISSN CPCHFT; ISSN 1439-4235
- Country of Publication:
- United States
- Language:
- ENGLISH
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