Sub-nanometer-resolution elemental mapping of "pt 3Co" nanoparticle catalyst degradation in proton-exchange membrane fuel cells

Christopher E. Carlton; Shuo Chen; Paulo J. Ferreira; Lawrence F. Allard; Yang Shao-Horn

doi:10.1021/jz2016022

Sub-nanometer-resolution elemental mapping of "pt ₃Co" nanoparticle catalyst degradation in proton-exchange membrane fuel cells

Christopher E. Carlton, Shuo Chen, Paulo J. Ferreira, Lawrence F. Allard, Yang Shao-Horn

Nuclear Energy Materials Microanalysis

Research output: Contribution to journal › Article › peer-review

75 Scopus citations

Abstract

The efficiency of proton exchange membrane fuel cells (PEMFCs) is limited largely by sluggish oxygen reduction reaction (ORR) kinetics, even when promoted by Pt-based alloy nanoparticles (NPs). Acid-leached Pt alloys such as "Pt ₃Co" have shown considerably higher specific (2-5 times) and mass (2 to 3 times) ORR activity than Pt NPs. However, the specific activity enhancement of "Pt ₃Co" NPs decreases during PEMFC operation, which has been attributed to the formation of a Pt-enriched shell near the NP surfaces. In this study, we report direct evidence of surface Pt and Co compositional changes in acid-treated "Pt ₃Co" NPs after PEMFC voltage cycling using energy-dispersive spectroscopy mapping in an aberration-corrected scanning transmission electron microscope with subnanometer resolution. Acid-treated "Pt ₃Co" NPs were found to have Pt-enriched shells of ∼0.5 nm, whereas the Pt-enriched-shell became thicker (∼1-6 nm) after PEMFC voltage cycling, where greater shell thicknesses were associated with larger "Pt ₃Co" NPs.

Original language	English
Pages (from-to)	161-166
Number of pages	6
Journal	Journal of Physical Chemistry Letters
Volume	3
Issue number	2
DOIs	https://doi.org/10.1021/jz2016022
State	Published - Jan 19 2012

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title = "Sub-nanometer-resolution elemental mapping of {"}pt 3Co{"} nanoparticle catalyst degradation in proton-exchange membrane fuel cells",

abstract = "The efficiency of proton exchange membrane fuel cells (PEMFCs) is limited largely by sluggish oxygen reduction reaction (ORR) kinetics, even when promoted by Pt-based alloy nanoparticles (NPs). Acid-leached Pt alloys such as {"}Pt 3Co{"} have shown considerably higher specific (2-5 times) and mass (2 to 3 times) ORR activity than Pt NPs. However, the specific activity enhancement of {"}Pt 3Co{"} NPs decreases during PEMFC operation, which has been attributed to the formation of a Pt-enriched shell near the NP surfaces. In this study, we report direct evidence of surface Pt and Co compositional changes in acid-treated {"}Pt 3Co{"} NPs after PEMFC voltage cycling using energy-dispersive spectroscopy mapping in an aberration-corrected scanning transmission electron microscope with subnanometer resolution. Acid-treated {"}Pt 3Co{"} NPs were found to have Pt-enriched shells of ∼0.5 nm, whereas the Pt-enriched-shell became thicker (∼1-6 nm) after PEMFC voltage cycling, where greater shell thicknesses were associated with larger {"}Pt 3Co{"} NPs.",

author = "Carlton, {Christopher E.} and Shuo Chen and Ferreira, {Paulo J.} and Allard, {Lawrence F.} and Yang Shao-Horn",

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AU - Carlton, Christopher E.

AU - Chen, Shuo

AU - Ferreira, Paulo J.

AU - Allard, Lawrence F.

AU - Shao-Horn, Yang

PY - 2012/1/19

Y1 - 2012/1/19

N2 - The efficiency of proton exchange membrane fuel cells (PEMFCs) is limited largely by sluggish oxygen reduction reaction (ORR) kinetics, even when promoted by Pt-based alloy nanoparticles (NPs). Acid-leached Pt alloys such as "Pt 3Co" have shown considerably higher specific (2-5 times) and mass (2 to 3 times) ORR activity than Pt NPs. However, the specific activity enhancement of "Pt 3Co" NPs decreases during PEMFC operation, which has been attributed to the formation of a Pt-enriched shell near the NP surfaces. In this study, we report direct evidence of surface Pt and Co compositional changes in acid-treated "Pt 3Co" NPs after PEMFC voltage cycling using energy-dispersive spectroscopy mapping in an aberration-corrected scanning transmission electron microscope with subnanometer resolution. Acid-treated "Pt 3Co" NPs were found to have Pt-enriched shells of ∼0.5 nm, whereas the Pt-enriched-shell became thicker (∼1-6 nm) after PEMFC voltage cycling, where greater shell thicknesses were associated with larger "Pt 3Co" NPs.

AB - The efficiency of proton exchange membrane fuel cells (PEMFCs) is limited largely by sluggish oxygen reduction reaction (ORR) kinetics, even when promoted by Pt-based alloy nanoparticles (NPs). Acid-leached Pt alloys such as "Pt 3Co" have shown considerably higher specific (2-5 times) and mass (2 to 3 times) ORR activity than Pt NPs. However, the specific activity enhancement of "Pt 3Co" NPs decreases during PEMFC operation, which has been attributed to the formation of a Pt-enriched shell near the NP surfaces. In this study, we report direct evidence of surface Pt and Co compositional changes in acid-treated "Pt 3Co" NPs after PEMFC voltage cycling using energy-dispersive spectroscopy mapping in an aberration-corrected scanning transmission electron microscope with subnanometer resolution. Acid-treated "Pt 3Co" NPs were found to have Pt-enriched shells of ∼0.5 nm, whereas the Pt-enriched-shell became thicker (∼1-6 nm) after PEMFC voltage cycling, where greater shell thicknesses were associated with larger "Pt 3Co" NPs.

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Sub-nanometer-resolution elemental mapping of "pt ₃Co" nanoparticle catalyst degradation in proton-exchange membrane fuel cells

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