Oxygen Electroreduction Activity and X-Ray Photoelectron Spectroscopy of Platinum and Early Transition Metal Alloys

Ifan E.L. Stephens, Alexander S. Bondarenko, Lone Bech, Ib Chorkendorff

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88 Scopus citations

Abstract

The oxygen reduction reaction (ORR) was studied experimentally on sputter-cleaned, polycrystalline electrodes of Pt 3Y, Pt 5Y, Pt 2Y, Pt 3Sc, Pt 3Hf, Pt 3Zr and Pt under conditions relevant for low-temperature fuel cells. The surfaces were characterised insitu by means of electrochemical methods and exsitu under ultrahigh vacuum conditions. The ORR activity was established in an electrochemical cell containing 0.1M HClO 4 by use of a rotating ring disk electrode assembly. The surface composition was characterised before and after the electrochemical measurements by using angle-resolved X-ray photoelectron spectroscopy. The ORR activity of the electrodes increased in the following order: Pt 2Y≈Pt 3Zr≈Pt≈<Pt 3Hf<Pt 3Sc≪Pt 5Y<Pt 3Y. At 23°C, the most active catalyst, Pt 3Y, exhibited a six- to ninefold improvement in activity over Pt in the potential range 0.9-0.87V with respect to a reversible hydrogen electrode. Over the same potential range at 60°C, Pt 3Y exhibited a four- to fivefold improvement in activity over Pt. The angle-resolved X-ray photoelectron spectroscopy analyses show that Pt 3Y and Pt 5Y formed a Pt overlayer under ORR conditions. In contrast, the surfaces of Pt 3Hf and Pt 3Zr comprised a mixture of Pt and HfO x or ZrO x, respectively, which explained their poor performance.

Original languageEnglish
Pages (from-to)341-349
Number of pages9
JournalChemCatChem
Volume4
Issue number3
DOIs
StatePublished - Mar 2012
Externally publishedYes

Keywords

  • Alloys
  • Electrochemistry
  • Energy conversion
  • Photoelectron spectroscopy
  • Reduction

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