Synthesis of ultrasmall, homogeneously alloyed, bimetallic nanoparticles on silica supports

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Science  15 Dec 2017:
Vol. 358, Issue 6369, pp. 1427-1430
DOI: 10.1126/science.aao6538
  • Fig. 1 SEA bimetallic adsorption schematic, adsorption density, and temperature-programmed reduction profiles.

    (A) Metal precursors electrostatically adsorb as a mixed monolayer. Clusters of alloyed NPs form after H2 reduction. (B) Adsorption surveys of noble and base metal pairs depict relative affinities of metals as a function of pH on the support. (C) TPR profiles (downward peaks indicate H2 consumption) of the monometallic SEA NPs are at a higher temperature, indicating a stronger support interaction relative to IMP nanoparticles. Bimetallic SEA NPs show improved reducibility from H2 spillover over the monometallic analogs.

  • Fig. 2 Bimetallic NP size characterization after reduction in 10% H2 balanced in He for 1 hour at 400°C.

    (A and C) XRD patterns and STEM images of co-SEA bimetallic NPs reveal extremely high dispersion. (B and D) XRD patterns and STEM images of co-IMP bimetallic samples show larger particles.

  • Fig. 3 Atomically resolved Z-contrast images showing NP speckling of alloys.

    (A and B) Pt-Co and Pt-Cu, separated by two rows in the table of elements. (C to E) Pd-Ni, Pd-Cu, and Pt-Pd, separated by one row. (F) Cu-Co, in the same row. Scale bars, 5 nm.

  • Table 1 Compositions (weight percent) of bimetallic NPs supported on silica.
    Co0.86 Co0.94 Ni/0.97 Co0.70 Cu/0.66 Co3.2 Pt/0.8 Co0.7 Co/1.3 Pd
    Ni 1.84 Ni0.89 Cu/0.63 Ni2.6 Pt/0.79 Ni0.52 Ni/1.2 Pd
    Cu 2.25 Cu2.2 Pt/0.94 Cu1.0 Cu/2.1 Pd
    Pt 0.95 Pt1.31 Pt/0.7 Pd
    Pd 1.27 Pd
  • Table 2 Average particle sizes of bimetallic NPs.

    STEM sizes are number-average diameters; XRD sizes are from the Scherrer equation.

    co-SEA STEM
    Pt-Pd1.0 ± 0.29.4
    Pt-Cu1.2 ± 0.32.8*
    Pt-Ni1.1 ± 0.36.9
    Pt-Co0.94 ± 0.34.2
    Cu-Co1.3 ± 0.37.3
    Cu-Ni1.1 ± 0.314
    Ni-Co1.4 ± 0.315.0*
    Pd-Ni1.1 ± 0.26.4
    Pd-Co1.0 ± 0.27.3
    Pd-Cu1.1 ± 0.214.5

    *2.8 nm is an average of three replicates (3.7, 2.5, and 2.3 nm); 15 is an average of 15.9, 15.2, and 13.9 nm.

    Supplementary Materials

    • Synthesis of ultrasmall, homogeneously alloyed, bimetallic nanoparticles on silica supports

      A. Wong, Q. Liu, S. Griffin, A. Nicholls, J. R. Regalbuto

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      • Materials and Methods
      • Figs. S1 to S6
      • Tables S1 to S12

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