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Structurally ordered intermetallic platinum–cobalt core–shell nanoparticles with enhanced activity and stability as oxygen reduction electrocatalysts

Abstract

To enhance and optimize nanocatalyst performance and durability for the oxygen reduction reaction in fuel-cell applications, we look beyond Pt–metal disordered alloys and describe a new class of Pt–Co nanocatalysts composed of ordered Pt3Co intermetallic cores with a 2–3 atomic-layer-thick platinum shell. These nanocatalysts exhibited over 200% increase in mass activity and over 300% increase in specific activity when compared with the disordered Pt3Co alloy nanoparticles as well as Pt/C. So far, this mass activity for the oxygen reduction reaction is the highest among the Pt–Co systems reported in the literature under similar testing conditions. Stability tests showed a minimal loss of activity after 5,000 potential cycles and the ordered core–shell structure was maintained virtually intact, as established by atomic-scale elemental mapping. The high activity and stability are attributed to the Pt-rich shell and the stable intermetallic Pt3Co core arrangement. These ordered nanoparticles provide a new direction for catalyst performance optimization for next-generation fuel cells.

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Figure 1: XRD and HAADF-STEM images.
Figure 2: ADF-STEM image of one nanoparticle and elemental mapping.
Figure 3: Electrochemical characterization.
Figure 4: Characterization of the surface area changes and stability for ORR.
Figure 5: Structural stability.

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Acknowledgements

This work was supported by the Department of Energy though grant DE-FG02-87ER45298, by the Energy Materials Center at Cornell, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001086. This work made use of TEM facilities of the Cornell Center for Materials Research, an National Science Foundation Materials Research Science and Engineering Center, under award number DMR-1120296. Y.Y. acknowledges the fellowship from American Chemical Society (ACS) Division of Analytical Chemistry sponsored by Eastman Chemical Company. H.L.X. acknowledges the help from J. A. Mundy for developing the method of extracting Pt and Co maps with improved signal to noise ratio.

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D.W. and H.L.X. conceived and designed the experiments. D.W. performed synthesis and electrochemical characterizations. H.L.X. performed STEM and EELS mapping experiments. D.W. and H.L.X. wrote the manuscript with assistance from R.H.D.W. and H.L.X. contributed equally to this work. R.H. participated in analysis of the data. All authors discussed the results and commented on the manuscript.

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Correspondence to Héctor D. Abruña.

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Wang, D., Xin, H., Hovden, R. et al. Structurally ordered intermetallic platinum–cobalt core–shell nanoparticles with enhanced activity and stability as oxygen reduction electrocatalysts. Nature Mater 12, 81–87 (2013). https://doi.org/10.1038/nmat3458

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