title: Design of Low Pt Concentration Electrocatalyst Surfaces with High Oxygen Reduction Reaction Activity Promoted by Formation of a Heterogeneous Interface between Pt and CeO(x) Nanowire.
abstract: Pt-CeO(x) 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 CeO(x) 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 CeO(x) nanoparticle (NP)/C was similar to that of 20 wt % Pt/C. To investigate the role of a CeO(x) NW promotor on the enhancement of ORR activity on Pt, the Pt-CeO(x) 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-CeO(x) NW interface in the electrocatalyst contains two different defect clusters: Frenkel defect clusters (i.e., 2Pt(i)(••) - 4O(i)″ - 4V(o)(••) - V(Ce)″″) formed in the surface around the Pt-CeO(x) NW interface and Schottky defect clusters (i.e., (Pt(Ce)″ - 2V(O)(••) - 2Ce(Ce)') and (Pt(Ce)″ - V(O)(••))) which appear in the bulk of the Pt-CeO(x) NW interface similarly to Pt-CeO(x) NP/C. It is concluded that the formation of both Frenkel defect clusters and Schottky defect clusters at the Pt-CeO(x) NW heterointerface contributes to the promotion of ORR activity and permits the use of lower Pt-loadings in these electrocatalysts.
authors.affiliation: Graduate School of Chemical Sciences and Engineering, Hokkaido University , Kita 13, Nishi 8, Kita-Ku Sapporo, Hokkaido 060-8628, Japan.
authors.forename: Shipra
authors.initials: S
authors.lastname: Chauhan
authors.affiliation: Graduate School of Chemical Sciences and Engineering, Hokkaido University , Kita 13, Nishi 8, Kita-Ku Sapporo, Hokkaido 060-8628, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Mori
authors.affiliation: Graduate School of Chemical Sciences and Engineering, Hokkaido University , Kita 13, Nishi 8, Kita-Ku Sapporo, Hokkaido 060-8628, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Masuda
authors.affiliation: Synchrotron X-ray Station at SPring-8, NIMS , Sayo, Hyogo 679-5148, Japan.|Quantum Beam Unit, NIMS , 1-2-1 Sengen, Ibaraki 305-0044, Japan.
authors.forename: Shigenori
authors.initials: S
authors.lastname: Ueda
authors.forename: Gary J
authors.initials: GJ
authors.lastname: Richards
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Hill
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Ariga
authors.affiliation: Transmission Electron Microscopy Station, NIMS , 1-2-1, Sengen, Ibaraki 305-0047, Japan.
authors.forename: Noriko
authors.initials: N
authors.lastname: Isaka
authors.affiliation: Centre for Microscopy and Microanalysis, The University of Queensland , St. Lucia, Brisbane, Queensland 4072, Australia.
authors.forename: Graeme
authors.initials: G
authors.lastname: Auchterlonie
authors.affiliation: Centre for Microscopy and Microanalysis, The University of Queensland , St. Lucia, Brisbane, Queensland 4072, Australia.
authors.forename: John
authors.initials: J
authors.lastname: Drennan
keywords: EELS analysis; Frenkel type defect cluster formation; HXPS analysis; ORR; Pt-CeOx nanowire/C cathode; heterointerface of Pt and CeOx nanowire