Mass-selected nanoparticles of PtxY as model catalysts for ​oxygen electroreduction

Journal name:
Nature Chemistry
Year published:
Published online


Low-temperature fuel cells are limited by the oxygen reduction reaction, and their widespread implementation in automotive vehicles is hindered by the cost of ​platinum, currently the best-known catalyst for reducing ​oxygen in terms of both activity and stability. One solution is to decrease the amount of ​platinum required, for example by alloying, but without detrimentally affecting its properties. The alloy PtxY is known to be active and stable, but its synthesis in nanoparticulate form has proved challenging, which limits its further study. Herein we demonstrate the synthesis, characterization and catalyst testing of model PtxY nanoparticles prepared through the gas-aggregation technique. The catalysts reported here are highly active, with a mass activity of up to 3.05 A mgPt−1 at 0.9 V versus a reversible hydrogen electrode. Using a variety of characterization techniques, we show that the enhanced activity of PtxY over elemental ​platinum results exclusively from a compressive strain exerted on the platinum surface atoms by the alloy core.

At a glance


  1. Surface characterization of the PtxY nanoparticles before and after ORR activity measurements.
    Figure 1: Surface characterization of the PtxY nanoparticles before and after ORR activity measurements.

    a, Schematic representation of the cluster source. bd, Representative surface characterization data for the as-prepared PtxY 9 nm particles. eg, Equivalent data for the PtxY 9 nm particles following exposure to the ORR conditions. b,e, ISS spectra. c,f, Detailed XPS survey of Pt 4f core-level region spectra. d,g, Detailed XPS survey of Y 3d core-level region spectra. Based on the XPS data, the Pt:Y ratio in the near-surface region of the as-prepared particles is four, whereas it is 14.3 for the particles after the ORR. a.u., arbitrary units; SEM, scanning electron microscope; UHV, ultrahigh vacuum.

  2. Particle-size distributions and representative TEM micrographs for the PtxY catalysts.
    Figure 2: Particle-size distributions and representative TEM micrographs for the PtxY catalysts.

    a, 4 nm. b, 5 nm. c, 7 nm. d, 9 nm.

  3. Catalyst activity of PtxY in nanoparticles in comparison to Pt.
    Figure 3: Catalyst activity of PtxY in nanoparticles in comparison to ​Pt.

    a,b, Surface specific activity (a) and mass activity (b) of PtxY (red). All data are taken at 0.9 V, recorded at 50 mV s−1, 1,600 revolutions per minute and 23 ± 1 °C in ​O2-saturated 0.1 M ​HClO4, taken from the anodic cycle and corrected for mass-transport limitations. For comparison, the previously published mass and specific activities of pure ​Pt nanoparticles, prepared in the same way, and an extended surface of polycrystalline ​Pt (Pt pc) are also plotted (black)40. The Supplementary Information gives details of the quantification of mass and surface area40. The Pt3Y pc data represent a sputter-cleaned extended surface of polycrystalline Pt3Y tested under the same conditions16. Each data point corresponds to the mean value from at least three independent activity tests; the error bars show the standard deviation in the electrochemical measurements and the PSD. The lines serve as a guide for the eye.

  4. High-angle annular dark-field (HAADF)-STEM images and EDS elemental maps for PtxY 9 nm.
    Figure 4: High-angle annular dark-field (HAADF)-STEM images and EDS elemental maps for PtxY 9 nm.

    Images for the as-prepared sample (ae) and for the catalyst after ORR conditions (fj). a,f, HAADF-STEM images. b,g, EDS elemental maps of ​Y Kα. c,h, EDS elemental maps of ​Pt Lα. d,i, Combined elemental maps of ​Pt + ​Y. e,j, EDS intensity line profiles extracted from the spectrum image data cube along the purple lines drawn on a and f. We estimated the ​Pt-shell thickness of the nanoparticles by extracting ten line profiles across each particle of f and obtained a value of 1.0 ± 0.3 nm.

  5. XAS analysis.
    Figure 5: XAS analysis.

    a, Average nearest-neighbour Pt–Pt distance measured by EXAFS as a function of the particle size for both as-prepared (black) and after ORR (red) recorded on PtxY. For the purpose of comparison, EXAFS measurements were also performed on as-prepared (blue) and electrochemically tested (red) ​Pt nanoparticles. Measurements were performed on a ​Pt foil (continuous grey horizontal line; the dashed grey horizontal lines show the error from the fitting software) as a reference. The left y axis shows the nearest neighbour Pt–Pt distance; the right axis represents the % strain in the Pt–Pt distance, relative to that of the bulk ​Pt-foil. The y-axis represents the % strain in the Pt–Pt distance relative to that in the ​Pt foil. b, Surface specific activity, extracted from Fig. 3, as a function of the average compressive strain in the PtxY particles relative to bulk ​Pt, based on the data shown in a. The error bars are produced by the fitting software (full details can be found in Supplementary Table 2). The continuous curved lines serve as a guide for the eye.


  1. Gasteiger, H. A., Kocha, S. S., Sompalli, B. & Wagner, F. T. Activity benchmarks and requirements for Pt, Pt-alloy, and non-Pt oxygen reduction catalysts for PEMFCs. Appl. Catal. B 56, 935 (2005).
  2. Gasteiger, H. A. & Markovic, N. M. Just a dream – or future reality? Science 324, 4849 (2009).
  3. Stephens, I. E. L., Bondarenko, A. S., Grønbjerg, U., Rossmeisl, J. & Chorkendorff, I. Understanding the oxygen reduction reaction on platinum and its alloys. Energy Environ. Sci. 5, 67446762 (2012).
  4. Debe, M. K. Electrocatalyst approaches and challenges for automotive fuel cells. Nature 486, 4351 (2012).
  5. Wagner, F. T., Lakshmanan, B. & Mathias, M. F. Electrochemistry and the future of the automobile. J. Phys. Chem. Lett. 1, 22042219 (2010).
  6. Chen, S., Gasteiger, H. A., Hayakawa, K., Tada, T. & Shao-Horn, Y. Platinum-alloy cathode catalyst degradation in proton exchange membrane fuel cells: nanometer-scale compositional and morphological changes. J. Electrochem. Soc. 157, A82A97 (2010).
  7. Maillard, F. et al. Durability of Pt3Co/C nanoparticles in a proton-exchange membrane fuel cell: direct evidence of bulk Co segregation to the surface. Electrochem. Commun. 12, 11611164 (2010).
  8. Cui, C. H., Gan, L., Heggen, M., Rudi, S. & Strasser, P. Compositional segregation in shaped Pt alloy nanoparticles and their structural behaviour during electrocatalysis. Nature Mater. 12, 765771 (2013).
  9. Wang, D. L. et al. Structurally ordered intermetallic platinum–cobalt core–shell nanoparticles with enhanced activity and stability as oxygen reduction electrocatalysts. Nature Mater. 12, 8187 (2013).
  10. Liu, W. et al. Bimetallic aerogels: high-performance electrocatalysts for the oxygen reduction reaction. Angew. Chem. Int. Ed. 52, 98499852 (2013).
  11. Sasaki, K. et al. Highly stable Pt monolayer on PdAu nanoparticle electrocatalysts for the oxygen reduction reaction. Nature Commun. 3, 1115 (2012).
  12. Wang, C. et al. Design and synthesis of bimetallic electrocatalyst with multilayered Pt-skin surfaces. J. Am. Chem. Soc. 133, 1439614403 (2011).
  13. Greeley, J. et al. Alloys of platinum and early transition metals as oxygen reduction electrocatalysts. Nature Chem. 1, 552556 (2009).
  14. Stamenkovic, V. R. et al. Improved oxygen reduction activity on Pt3Ni(111) via increased surface site availability. Science 315, 493497 (2007).
  15. Stephens, I. E. L., Bondarenko, A. S., Bech, L. & Chorkendorff, I. Oxygen electroreduction activity and X-ray photoelectron spectroscopy of alloys of platinum and early transition metals. ChemCatChem 4, 341349 (2012).
  16. Escudero-Escribano, M. et al. Pt5Gd as a highly active and stable catalyst for oxygen electroreduction. J. Am. Chem. Soc. 134, 1647616479 (2012).
  17. Johannesson, G. H. et al. Combined electronic structure and evolutionary search approach to materials design. Phys. Rev. Lett. 88, 255506 (2002).
  18. Jong Yoo, S. et al. Enhanced stability and activity of Pt–Y alloy catalysts for electrocatalytic oxygen reduction. Chem. Commun. 47, 1141411416 (2011).
  19. Hwang, S. J. et al. Role of electronic perturbation in stability and activity of Pt-based alloy nanocatalysts for oxygen reduction. J. Am. Chem. Soc. 134, 1950819511 (2012).
  20. Sanchez Casalongue, H. et al. Direct observation of the oxygenated species during oxygen reduction on a platinum fuel cell cathode. Nature Commun. 4, 2817 (2013).
  21. Toda, T., Igarashi, H., Uchida, H. & Watanabe, M. Enhancement of the electroreduction of oxygen on Pt alloys with Fe, Ni, and Co. J. Electrochem. Soc. 146, 37503756 (1999).
  22. Stamenkovic, V. R., Mun, B. S., Mayrhofer, K. J. J., Ross, P. N. & Markovic, N. M. Effect of surface composition on electronic structure, stability, and electrocatalytic properties of Pt–transition metal alloys: Pt-skin versus Pt-skeleton surfaces. J. Am. Chem. Soc. 128, 88138819 (2006).
  23. Yang, R. Z., Strasser, P. & Toney, M. F. Dealloying of Cu3Pt (111) studied by surface X-ray scattering. J. Phys. Chem. C 115, 90749080 (2011).
  24. Stephens, I. E. L. et al. Tuning the activity of Pt(111) for oxygen electroreduction by subsurface alloying. J. Am. Chem. Soc. 133, 54855491 (2011).
  25. Strasser, P. et al. Lattice-strain control of the activity in dealloyed core–shell fuel cell catalysts. Nature Chem. 2, 454460 (2010).
  26. Johansson, T. et al. Pt skin versus Pt skeleton structures of Pt3Sc as electrocatalysts for oxygen reduction. Top. Catal. 57, 245254 (2014).
  27. Nørskov, J. K. et al. Origin of the overpotential for oxygen reduction at a fuel-cell cathode. J. Phys. Chem. B 108, 1788617892 (2004).
  28. Kitchin, J. R., Nørskov, J. K., Barteau, M. A. & Chen, J. G. Role of strain and ligand effects in the modification of the electronic and chemical properties of bimetallic surfaces. Phys. Rev. Lett. 93, 156801 (2004).
  29. Calle-Vallejo, F., Martinez, J. I., Garcia-Lastra, J. M., Rossmeisl, J. & Koper, M. T. M. Physical and chemical nature of the scaling relations between adsorption energies of atoms on metal surfaces. Phys. Rev. Lett. 108, 116103 (2012).
  30. Mavrikakis, M., Hammer, B. & Nørskov, J. K. Effect of strain on the reactivity of metal surfaces. Phys. Rev. Lett. 81, 28192822 (1998).
  31. Cordero, B. et al. Covalent radii revisited. Dalton Trans. 28322838 (2008).
  32. Pourbaix, M. Atlas of Electrochemical Equilibria in Aqueous Solutions 2nd edn (National Association of Corrosion Engineers, 1974).
  33. Nishanth, K. G., Sridhar, P. & Pitchumani, S. Enhanced oxygen reduction reaction activity through spillover effect by Pt–Y(OH)3/C catalyst in direct methanol fuel cells. Electrochem. Commun. 13, 14651468 (2011).
  34. Jeon, M. K. & McGinn, P. J. Carbon supported Pt–Y electrocatalysts for the oxygen reduction reaction. J. Power Sources 196, 11271131 (2011).
  35. Luczak, F. J. & Landsman, D. A. Fuel cell cathode catalyst alloy-comprising noble metal, cobalt and a transition metal. US patent 4677092-A (1987).
  36. Mukerjee, S. & Srinivasan, S. Enhanced electrocatalysis of oxygen reduction on platinum alloys in proton-exchange membrane fuel-cells. J. Electroanal. Chem. 357, 201224 (1993).
  37. van der Vliet, D. F. et al. Mesostructured thin films as electrocatalysts with tunable composition and surface morphology. Nature Mater. 11, 10511058 (2012).
  38. Snyder, J., Fujita, T., Chen, M. W. & Erlebacher, J. Oxygen reduction in nanoporous metal–ionic liquid composite electrocatalysts. Nature Mater. 9, 904907 (2010).
  39. Nesselberger, M. et al. The effect of particle proximity on the oxygen reduction rate of size-selected platinum clusters. Nature Mater. 12, 919924 (2013).
  40. Perez-Alonso, F. J. et al. The effect of size on the oxygen electroreduction activity of mass-selected platinum nanoparticles. Angew. Chem. Int. Ed. 51, 46414643 (2012).
  41. Li, Z. Y. et al. Structures and optical properties of 4–5 nm bimetallic AgAu nanoparticles. Faraday Discuss. 138, 363373 (2008).
  42. Yin, F., Wang, Z. W. & Palmer, R. E. Controlled formation of mass-selected Cu–Au core–shell cluster beams. J. Am. Chem. Soc. 133, 1032510327 (2011).
  43. Von Issendorff, B. & Palmer, R. E. A new high transmission infinite range mass selector for cluster and nanoparticle beams. Rev. Sci. Instrum. 70, 44974501 (1999).
  44. Li, D. G. et al. Surfactant removal for colloidal nanoparticles from solution synthesis: the effect on catalytic performance. ACS Catal. 2, 13581362 (2012).
  45. Solla-Gullon, J., Montiel, V., Aldaz, A. & Clavilier, J. Electrochemical characterisation of platinum nanoparticles prepared by microemulsion: how to clean them without loss of crystalline surface structure. J. Electroanal. Chem. 491, 6977 (2000).
  46. Cuenya, B. R., Baeck, S. H., Jaramillo, T. F. & McFarland, E. W. Size- and support-dependent electronic and catalytic properties of Au0/Au3+ nanoparticles synthesized from block copolymer micelles. J. Am. Chem. Soc. 125, 1292812934 (2003).
  47. Reichl, R. & Gaukler, K. H. An investigation of air-grown yttrium oxide and experimental determination of the sputtering yield and the inelastic mean free path. Appl. Surf. Sci. 26, 196210 (1986).
  48. Shao-Horn, Y. et al. Instability of supported platinum nanoparticles in low-temperature fuel cells. Top. Catal. 46, 285305 (2007).
  49. Choi, S. I. et al. Synthesis and characterization of 9 nm Pt–Ni octahedra with a record high activity of 3.3 A/mgPt for the oxygen reduction reaction. Nano Lett. 13, 34203425 (2013).
  50. Nesselberger, M. et al. The particle size effect on the oxygen reduction activity of Pt catalysts: influence of electrolyte and relation to single crystal models. J. Am. Chem. Soc. 133, 1742817433 (2011).

Download references

Author information


  1. Center for Individual Nanoparticle Functionality, Department of Physics, Technical University of Denmark, Kgs Lyngby DK-2800, Denmark

    • Patricia Hernandez-Fernandez,
    • Federico Masini,
    • David N. McCarthy,
    • Christian E. Strebel,
    • Paolo Malacrida,
    • Anders Nierhoff,
    • Anders Bodin,
    • Jane H. Nielsen,
    • Ifan E. L. Stephens &
    • Ib Chorkendorff
  2. SLAC National Accelerator Laboratory, 2575 Sand Hill Road, MS31, Menlo Park CA 94025, USA

    • Daniel Friebel,
    • Anna M. Wise &
    • Anders Nilsson
  3. Center for Electron Nanoscopy, Technical University of Denmark, Kgs Lyngby DK-2800, Denmark

    • Davide Deiana &
    • Thomas W. Hansen


I.C. and I.E.L.S. conceived the experiments. P.H-F. performed the electrochemical experiments. F.M., D.N.M., C.E.S., P.M. and A.N. performed the UHV experiments. D.F., A.B. and A.M.W performed the XAS measurements. D.D. performed the microscopy. P.H-F. designed the figures. P.H-F. and I.E.L.S. wrote the first draft of the paper. All authors discussed the results and commented on the manuscript.

Competing financial interests

I.C. and I.E.L.S. have a patent on the catalyst material PtxY, PCT/DK2010/050193. The other authors declare no competing financial interests.

Corresponding authors

Correspondence to:

Author details

Supplementary information

PDF files

  1. Supplementary information (1,418 KB)

    Supplementary information

Additional data