Design of Low Pt Concentration Electrocatalyst Surfaces with High Oxygen Reduction Reaction Activity Promoted by Formation of a Heterogeneous Interface between Pt and CeOx Nanowire

Shipra Chauhan, Toshiyuki Mori, Takuya Masuda, Shigenori Ueda, Gary J. Richards, Jonathan P. Hill, Katsuhiko Ariga, Noriko Isaka, Graeme Auchterlonie, John Drennan

Research output: Contribution to journalArticlepeer-review

35 Citations (Scopus)

Abstract

Pt-CeOx nanowire (NW)/C electrocatalysts for the improvement of oxygen reduction reaction (ORR) activity on Pt were prepared by a combined process involving precipitation and coimpregnation. A low, 5 wt % Pt-loaded CeOx NW/C electrocatalyst, pretreated by an optimized electrochemical conditioning process, exhibited high ORR activity over a commercially available 20 wt % Pt/C electrocatalyst although the ORR activity observed for a 5 wt % Pt-loaded CeOx nanoparticle (NP)/C was similar to that of 20 wt % Pt/C. To investigate the role of a CeOx NW promotor on the enhancement of ORR activity on Pt, the Pt-CeOx NW interface was characterized by using hard X-ray photoelectron spectroscopy (HXPS), transmission electron microscopy (TEM), and electron energy loss spectroscopy (EELS). Microanalytical data obtained by these methods were discussed in relation to atomistic simulation performed on the interface structures. The combined techniques of HXPS, TEM-EELS, and atomistic simulation indicate that the Pt-CeOx NW interface in the electrocatalyst contains two different defect clusters: Frenkel defect clusters (i.e., 2Pti•• - 4Oi″ - 4Vo•• - VCe″″) formed in the surface around the Pt-CeOx NW interface and Schottky defect clusters (i.e., (PtCe″ - 2VO•• - 2CeCe′) and (PtCe″ - VO••)) which appear in the bulk of the Pt-CeOx NW interface similarly to Pt-CeOx NP/C. It is concluded that the formation of both Frenkel defect clusters and Schottky defect clusters at the Pt-CeOx NW heterointerface contributes to the promotion of ORR activity and permits the use of lower Pt-loadings in these electrocatalysts.

Original languageEnglish
Pages (from-to)9059-9070
Number of pages12
JournalACS Applied Materials and Interfaces
Volume8
Issue number14
DOIs
Publication statusPublished - 2016 Apr 27
Externally publishedYes

Keywords

  • EELS analysis
  • Frenkel type defect cluster formation
  • heterointerface of Pt and CeO nanowire
  • HXPS analysis
  • ORR
  • Pt-CeO nanowire/C cathode

ASJC Scopus subject areas

  • Materials Science(all)

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