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Title: Activity-Stability Relationships of Ordered And Disordered Alloy Phases of Pt3Co Electrocatalysts for the Oxygen Reduction Reaction (ORR)

Abstract

No abstract prepared.

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Stanford Linear Accelerator Center (SLAC)
Sponsoring Org.:
USDOE
OSTI Identifier:
901833
Report Number(s):
SLAC-REPRINT-2007-021
Journal ID: ISSN 0013-4686; ELCAAV; TRN: US200717%%81
DOE Contract Number:
AC02-76SF00515
Resource Type:
Journal Article
Resource Relation:
Journal Name: Electrochim.Acta 52:2765-2774,2007; Journal Volume: 52
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ALLOYS; CATALYTIC EFFECTS; COBALT ALLOYS; ELECTROCATALYSTS; OXYGEN; PHASE STUDIES; PLATINUM BASE ALLOYS; REDOX REACTIONS; STABILITY; Other,OTHER

Citation Formats

Koh, S., /Houston U., Toney, M.F., /SLAC, SSRL, Strasser, P., and /Houston U. Activity-Stability Relationships of Ordered And Disordered Alloy Phases of Pt3Co Electrocatalysts for the Oxygen Reduction Reaction (ORR). United States: N. p., 2007. Web. doi:10.1016/j.electacta.2006.08.039.
Koh, S., /Houston U., Toney, M.F., /SLAC, SSRL, Strasser, P., & /Houston U. Activity-Stability Relationships of Ordered And Disordered Alloy Phases of Pt3Co Electrocatalysts for the Oxygen Reduction Reaction (ORR). United States. doi:10.1016/j.electacta.2006.08.039.
Koh, S., /Houston U., Toney, M.F., /SLAC, SSRL, Strasser, P., and /Houston U. Fri . "Activity-Stability Relationships of Ordered And Disordered Alloy Phases of Pt3Co Electrocatalysts for the Oxygen Reduction Reaction (ORR)". United States. doi:10.1016/j.electacta.2006.08.039.
@article{osti_901833,
title = {Activity-Stability Relationships of Ordered And Disordered Alloy Phases of Pt3Co Electrocatalysts for the Oxygen Reduction Reaction (ORR)},
author = {Koh, S. and /Houston U. and Toney, M.F. and /SLAC, SSRL and Strasser, P. and /Houston U.},
abstractNote = {No abstract prepared.},
doi = {10.1016/j.electacta.2006.08.039},
journal = {Electrochim.Acta 52:2765-2774,2007},
number = ,
volume = 52,
place = {United States},
year = {Fri Apr 06 00:00:00 EDT 2007},
month = {Fri Apr 06 00:00:00 EDT 2007}
}
  • Electrocatalysts consisting of polypyrrole (PPY) and Co deposited on carbon black (CB) at several compositions were prepared and tested for the oxygen reduction reaction (ORR) in a HClO4 buffer (pH = 1) using a rotating ring-disk electrode (RRDE). It was determined that the most favorable catalyst composition (prior to calcination) had a CB:PPY weight ratio of 2 and a pyrrole:Co (i.e., PY:Co) molar ratio of 4. This catalyst had an onset potential of 0.785 V (vs. RHE) and a mass activity of ca. 1 A/g{sub cata} at the fuel cell relevant voltage of 0.65 V. Furthermore, it was found thatmore » the number of electrons exchanged during the ORR with the catalyst was ca. 3.5 and resulted in 28% yield of H{sub 2}O{sub 2} at 0.65 V, which hints to an indirect 4e{sup -} reduction of O{sub 2} to H{sub 2}O, with H{sub 2}O{sub 2} as an intermdiate. From energy dispersive spectroscopy (EDS) and extended X-ray absorption fine structure (EXAFS) analysis, it is proposed that a PY:Co ratio of 4 favors the formation, prior to calcination, in the catalyst precursor of Co-N complexes in which Co is coordinated to 3 or 4 N atoms, resulting in strong Co-N interactions that limit the formation upon calcination of low ORR activity Co nanoparticles. These Co-N complexes give rise upon calcination to CoN{sub x-2} sites in which the coordination of Co could favor the adsorption on them of O{sub 2}, which would make those sites particularly active and selective. At the same mass acitivity of 1 A/g{sub cata}, the voltage yielded by the catalyst was 200 mV lower than that for a state-of-the-art Pt (10 wt.%) catalyst, whoch H{sub 2}O{sub 2} output at 0.85 V was 39% and involves the exchange of 3.2 e{sup -}, overall making our material an attractive substitute to noble metal ORR electrocatalysts.« less
  • We describe the synthesis and electrocatalytic properties of a new low-Pt electrocatalyst consisting of an IrCo core, a Pd interlayer, and a surface Pt monolayer, emphasizing the interlayer's role in improving electrocatalytic activity for the oxygen-reduction reaction on Pt in HClO{sub 4} solution. We prepared the IrCo alloys by decomposing, at 800 C, hexacyanometalate, KCoIr(CN){sub 6}, adsorbed on the carbon surfaces. The synthesis of Ir{sub 3}Co/C involved heating a mix of metal salts and carbon in hydrogen at 500 C. Thereafter, we placed a palladium and/or platinum monolayer on them via the galvanic displacement of an underpotentially deposited copper monolayer.more » The electrocatalysts were characterized using structural- and electrochemical-techniques. For PtML/PdML/IrCo/C, we observed a Pt mass activity of 1.18 A/mg{sub (Pt)} and the platinum-group-metals mass of 0.16 A/mg{sub (Pt, Pd, Ir)}. In comparison, without a Pd interlayer, i.e., Pt{sub ML}/IrCo/C, the activities of 0.15 A/mg{sub (Pt)} and 0.036 A/mg{sub (Pt, Pd, Ir)} were considerably lower. We consider that the palladium interlayer plays an essential role in achieving high catalytic activity by adjusting the electronic interaction of the platinum monolayer with the IrCo core, so that it accelerates the kinetics of adsorption and desorption of the intermediates of oxygen reduction. A similar trend was observed for Pt{sub ML}/Pd{sub ML} and Pt{sub ML} deposited on Ir{sub 3}Co/C alloy core. We used density functional theory to interpret the observed phenomena.« less