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Pd3Fe and Pt Monolayer-Modified Pd3Fe Electrocatalysts for Oxygen Reduction

Authors
  • Shao, M. H.
  • Sasaki, K.
  • Liu, P.
  • Adzic, R. R.
Type
Published Article
Journal
Zeitschrift für Physikalische Chemie
Publisher
De Gruyter
Publication Date
Oct 01, 2007
Volume
221
Issue
9-10
Pages
1175–1190
Identifiers
DOI: 10.1524/zpch.2007.221.9-10.1175
Source
De Gruyter
Keywords
License
Yellow

Abstract

In a search for electrocatalysts based on other metals with comparable attributes to very scarce and expensive Pt, we studied the kinetics of the oxygen reduction reaction (ORR) on carbon-supported Pd3Fe alloy nanoparticles in HClO4 and NaOH solutions. In acid solution, the electrocatalyst's activity for the ORR is slightly higher than that of commercial Pt/C. The reaction kinetics involves predominantly a four-electron reduction with the first charge-transfer step being the rate-determining one. The synthesis of a Pd overlayer on the Pd3Fe alloy's surface at elevated temperatures is due to strong segregation effects. The major cause of this electrocatalyst's high activity appears to be the downshifting of the d-band center of Pd overlayer, resulting in a weaker interaction between the oxygen-containing species and the Pd surface. We demonstrated a further enhancement of the ORR kinetics with a Pt monolayer-covered Pd3Fe/C electrocatalyst. In HClO4 solution, the mass-specific activity of Pt/Pd3Fe/C was about five times higher than that of commercial Pt/C, surpassing the Pt/Pd/C. In situ XANES data indicate that this elevated ORR activity may be due to the decreased formation of PtOH, and weaker oxygen adsorption on Pt/Pd3Fe/C.

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