Improving electrocatalysts for O2 reduction by fine-tuning the Pt-support interaction: Pt monolayer on the surfaces of a Pd3Fe(111) single-crystal alloy

Wei Ping Zhou, Xiaofang Yang, Miomir B. Vukmirovic, Bruce E. Koel, Jiao Jiao, Guowen Peng, Manos Mavrikakis, Radoslav R. Adzic

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177 Scopus citations

Abstract

We improved the effectiveness of Pt monolayer electrocatalysts for the oxygen-reduction reaction (ORR) using a novel approach to fine-tuning the Pt monolayer interaction with its support, exemplified by an annealed Pd 3Fe(111) single-crystal alloy support having a segregated Pd layer. Low-energy ion scattering and low-energy electron diffraction studies revealed that a segregated Pd layer, with the same structure as Pd (111), is formed on the surface of high-temperature-annealed Pd3Fe(111). This Pd layer is considerably more active than Pd(111); its ORR kinetics is comparable to that of a Pt(111) surface. The enhanced catalytic activity of the segregated Pd layer compared to that of bulk Pd apparently reflects the modification of Pd surface's electronic properties by underlying Fe. The Pd3Fe(111) suffers a large loss in ORR activity when the subsurface Fe is depleted by potential cycling (i.e., repeated excursions to high potentials in acid solutions). The Pd3Fe(111) surface is an excellent substrate for a Pt monolayer ORR catalyst, as verified by its enhanced ORR kinetics on PT ML/Pd/Pd3Fe(111). Our density functional theory studies suggest that the observed enhancement of ORR activity originates mainly from the destabilization of OH binding and the decreased Pt-OH coverage on the Pt/Pd/Pd3Fe(111) surface. The activity of PtML/Pd(111) and Pt(111) is limited by OH removal, whereas the activity of Pt ML/Pd/Pd3Fe(111) is limited by the O-O bond scission, which places these two surfaces on the two sides of the volcano plot.

Original languageEnglish (US)
Pages (from-to)12755-12762
Number of pages8
JournalJournal of the American Chemical Society
Volume131
Issue number35
DOIs
StatePublished - Sep 9 2009
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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