Research ArticleNANOPARTICLES

Octahedral palladium nanoparticles as excellent hosts for electrochemically adsorbed and absorbed hydrogen

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Science Advances  03 Feb 2017:
Vol. 3, no. 2, e1600542
DOI: 10.1126/sciadv.1600542
  • Fig. 1 Physical and electrochemical characterization of octahedral Pd-NPs.

    (A) HR-TEM image of octahedral Pd-NPs. The inset shows an image of a single NP and the corresponding FFT pattern. (B) Histogram showing the NP size (l) distribution. (C) IL-TEM images of the octahedral Pd-NPs before and after potential cycling in the range of 0 to 0.40 V. (D) CV profile for octahedral Pd-NPs acquired in 0.5 M aqueous H2SO4 solution at T = 296 K and s = 1.0 mV s−1 in the range of −0.05 to 0.40 V. The purple and red transients refer to UPD H (shown in detail in the inset), the green and blue transients refer to H absorption and Habs desorption, and the black transient refers to HER. RHE, reversible hydrogen electrode. (E) CV profiles for HUPD adsorption (shades of purple) and desorption (shades of red), and (F) CV profiles for H absorption (shades of green) and Habs desorption (shades of blue) for five temperature values acquired in 0.5 M aqueous H2SO4 solution at s = 1.0 mV s−1.

  • Fig. 2 Thermodynamical data for adsorption and desorption of HUPD on octahedral Pd-NPs.

    (A) Adsorption and desorption isotherms for HUPD on octahedral Pd-NPs at five temperatures in the range of 296 ≤ T ≤ 333 K. (B) Plots of Δec-adsG°(HUPD) and Δec-desG°(HUPD) as a function of θH for the five temperature values. (C) Plots of Δec-adsH°(HUPD) and Δec-desH°(HUPD) as a function of θH for the five temperature values. (D) Plots of Embedded Image as a function of θH for the five temperature values.

  • Fig. 3 Thermodynamical data for H absorption and Habs desorption in octahedral Pd-NPs.

    H absorption and Habs desorption isotherms expressed as E versus XH (A) and Embedded Image versus XH (B) at five temperature values in the range of 296 ≤ T ≤ 333 K. (C) van’t Hoff plots of Embedded Image versus 1/T for 0.10 ≤ XH ≤ 0.80. (D) Plots of Δec-absH°(Habs) and Δec-desH°(Habs) as a function of XH.

  • Fig. 4 Visual representation of the different steps of HUPD adsorption and H absorption in octahedral Pd-NPs.

    (A) HUPD species that occupy the octahedral sites beneath the first Pd surface layer. (B) Habs beneath the second and third Pd monolayers; HUPD, Habs, and the four topmost Pd layers that together form the shell region. (C) Habs in the core of the Pd-NP.

  • Fig. 5 Surface stress model for H absorption in and Habs desorption from octahedral Pd-NPs.

    (A) Visual representation of the cross section of a single octahedral Pd-NP loaded with H to XH = 0.90 showing HUPD beneath the first Pd layer, Habs in the shell region, and Habs in the NP core. (B) Comparison of the calculated H2(g) fugacity values (black line) to the experimentally determined data (red points) required to reach XH = 0.90.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/2/e1600542/DC1

    Results

    fig. S1. TEM image for cubic Pd-NPs and CV profiles of HUPD adsorption and desorption, H absorption, and Habs desorption.

    fig. S2. Plots of δΔG°(HUPD) as a function of θH for the five temperature values.

    fig. S3. Plots of Δec-adsS°(HUPD) (purple) and Δec-desS°(HUPD) (red) as a function of θH.

    fig. S4. Plots of δΔH°(HUPD) as a function of θH for the five temperature values.

    fig. S5. Adsorption and desorption isotherms for HUPD; plots of Δec-adsG°(HUPD), Δec-desG°(HUPD), Δec-adsH°(HUPD), Δec-desH°(HUPD); and Formula as a function of θH for the five temperature values.

    fig. S6. H absorption and Habs desorption isotherms, van’t Hoff plots, and plots of Δec-absH°(Habs) and Δec-desH°(Habs) as a function of XH for the five temperature values.

    fig. S7. Plot of δΔH°(Habs) as a function of XH.

    fig. S8. Plots of Δec-absS°(Habs) and Δec-desS°(Habs) as a function of XH.

    fig. S9. Plots of Δec-absG°(Habs), Δec-desG°(Habs), and δΔG°(Habs) as a function of XH for the five temperature values.

    fig. S10. Visualization of the Oh and Td sites on the fcc(111) surface.

    fig. S11. Variation of Formula as a function of XH.

    table S1. Properties of 0.50 M aqueous H2SO4 solution.

    References (31, 32)

  • Supplementary Materials

    This PDF file includes:

    • Results
    • fig. S1. TEM image for cubic Pd-NPs and CV profiles of HUPD adsorption and desorption, H absorption, and Habs desorption.
    • fig. S2. Plots of δΔG°(HUPD) as a function of θH for the five temperature values.
    • fig. S3. Plots of Δec-adsS°(HUPD) (purple) and Δec-desS°(HUPD) (red) as a function of θH.
    • fig. S4. Plots of δΔH°(HUPD) as a function of θH for the five temperature values.
    • fig. S5. Adsorption and desorption isotherms for HUPD; plots of Δec-adsG°(HUPD), Δec-desG°(HUPD), Δec-adsH°(HUPD), Δec-desH°(HUPD); and EPd HUPD as a function of θH for the five temperature values.
    • fig. S6. H absorption and Habs desorption isotherms, van’t Hoff plots, and plots of Δec-absH°(Habs) and Δec-desH°(Habs) as a function of XH for the five temperature values.
    • fig. S7. Plot of δΔH°(Habs) as a function of XH.
    • fig. S8. Plots of Δec-absS°(Habs) and Δec-desS°(Habs) as a function of XH.
    • fig. S9. Plots of Δec-absG°(Habs), Δec-desG°(Habs), and δΔG°(Habs) as a function of XH for the five temperature values.
    • fig. S10. Visualization of the Oh and Td sites on the fcc(111) surface.
    • fig. S11. Variation of Δμe- (XH) as a function of XH.
    • table S1. Properties of 0.50 M aqueous H2SO4 solution.
    • References (31, 32)

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