Research ArticleELECTROCHEMISTRY

Surface-modulated palladium-nickel icosahedra as high-performance non-platinum oxygen reduction electrocatalysts

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Science Advances  13 Jul 2018:
Vol. 4, no. 7, eaap8817
DOI: 10.1126/sciadv.aap8817
  • Fig. 1 Morphological and structural characterization of Pd6Ni icosahedra.

    (A) TEM image, (B) EDX, and (C) PXRD pattern of Pd6Ni icosahedra. (D) HRTEM (the threefold symmetry orientation was outlined by three yellow dotted lines) and (E) corresponding FFT image of Pd6Ni icosahedra (red circles indicated the diffraction spots). (F) HAADF-STEM image, (G) corresponding elemental mappings, and (H) line-scan analysis across the blue arrow in the inset of (F).

  • Fig. 2 Morphological and structural characterizations of Pd3Ni, Pd4Ni, and Pd8Ni icosahedra.

    (A, D, and G) TEM images, (B, E, and H) HAADF-STEM images and corresponding elemental mappings, and (C, F, and I) line-scan analysis of (A to C) Pd3Ni icosahedra, (D to F) Pd4Ni icosahedra, and (G to I) Pd8Ni icosahedra, respectively.

  • Fig. 3 ORR performance of Pd-Ni/C, commercial Pd/C, and commercial Pt/C.

    (A) CV curves of Pd-Ni/C and the commercial Pd/C recorded in 1 M KOH solution at a scan rate of 100 mV s−1. (B) ORR polarization curves of Pd-Ni/C and the commercial Pd/C recorded in O2-saturated 0.1 M KOH solution at a scan rate of 10 mV s−1 and a rotation rate of 1600 rpm. (C) Comparison of specific activities at 0.9 V versus RHE for these catalysts. (D) Comparison of mass activities at 0.9 V versus RHE for these catalysts and the commercial Pt/C. The activities were calculated on the basis of five independent measurements.

  • Fig. 4 Structural characterizations and ORR performance of Pd6Ni/C-400°C and Pd6Ni/C-500°C.

    (A and D) HAADF-STEM images, (B and E) corresponding elemental mappings from the area outlined by the red dotted line in (A) and (D), respectively, and (C and F) line-scan analysis across the blue arrow in the inset of (A) and (D), respectively, of (A to C) Pd6Ni-400°C and (D to F) Pd6Ni-500°C. (G) ORR polarization curves of Pd6Ni/C, Pd6Ni/C-400°C, and Pd6Ni/C-500°C recorded in 0.1 M KOH solution at a scan rate of 10 mV s−1. The activities were calculated on the basis of five independent measurements. (H) Electron transfer number of Pd6Ni icosahedra, Pd6Ni/C-400°C, Pd6Ni/C-500°C, and the commercial Pt/C.

  • Fig. 5 ORR performance of Pd6Ni/C, Pd6Ni/C-400°C, Pd6Ni/C-500°C, and the commercial Pt/C.

    ORR polarization curves of (A) the commercial Pt/C, (B) Pd6Ni/C, (C) Pd6Ni/C-400°C, and (D) Pd6Ni/C-500°C before and after 10,000 cycles. The insets show corresponding mass activities at 0.9 V versus RHE before and after 10,000 cycles.

  • Fig. 6 DFT simulations of the adsorption energy of adsorbed oxygen atom and the d-band center shift of PdxNi (111) with different ratios of Ni.

    (A) Adsorption energy of adsorbed oxygen atom with the change of Pd/Ni ratio. (B) Relationship between adsorption energy of oxygen and d-band center of Pd. The inset is the charge density difference of oxygen adsorbed on the surface of PdxNi (blue and yellow isosurfaces indicate electron depletion and electron accumulation with the same isosurface values of 0.005 e/bohr3; the silver and orange balls represent Pd and Ni atoms, respectively).

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/7/eaap8817/DC1

    Fig. S1. Lower-magnification TEM image, size distribution, and statistical results of the Pd6Ni icosahedra.

    Fig. S2. HRTEM images, corresponding FFT images, and geometrical models of Pd6Ni icosahedra oriented along three typical projections.

    Fig. S3. SEM-EDX and ICP-AES results of Pd3Ni icosahedra, Pd4Ni icosahedra, and Pd8Ni icosahedra.

    Fig. S4. XRD patterns of Pd3Ni icosahedra, Pd4Ni icosahedra, and Pd8Ni icosahedra.

    Fig. S5. HRTEM images of Pd3Ni icosahedra, Pd4Ni icosahedra, and Pd8Ni icosahedra.

    Fig. S6. XPS spectra of Pd 3d and Ni 2p for PdxNi/C.

    Fig. S7. TEM images of products under the typical condition but varying the amounts of Ni(HCO2)2·2H2O.

    Fig. S8. TEM images of products under the typical condition but varying the amounts of AA.

    Fig. S9. TEM images of products under the typical condition but changing the Ni(HCO2)2·2H2O to Ni(acac)2 and NiAc2.

    Fig. S10. TEM images, SEM-EDX results, and PXRD patterns of Pd-Ni icosahedron intermediates.

    Fig. S11. TEM images of Pd3Ni/C, Pd4Ni/C, Pd6Ni/C, and Pd8Ni/C.

    Fig. S12. TEM images of the commercial Pd/C.

    Fig. S13. CV curves of Pd-Ni/C, the commercial Pd/C, and the commercial Pt/C.

    Fig. S14. TEM images and HRTEM images of Pd6Ni/C-400°C and Pd6Ni/C-500°C.

    Fig. S15. ORR polarization curves for the commercial Pt/C, Pd6Ni/C, Pd6Ni/C-400°C, and Pd6Ni/C-500°C at different rotation rates.

    Fig. S16. TEM images of the commercial Pt/C before and after ORR durability tests.

    Fig. S17. TEM images and SEM-EDS patterns of Pd6Ni/C, Pd6Ni/C-400°C, and Pd6Ni/C-500°C after ORR durability tests.

    Fig. S18. Detailed characterizations of Pd6Ni/C after ORR durability test.

    Fig. S19. XPS spectra of Pd 3d and Ni 2p for the Pd6Ni/C before and after durability test.

    Fig. S20. Surface valence bands of PdxNi/C.

    Fig. S21. TEM images, image of ~50 ml of Pd6Ni icosahedra colloidal solution, and statistical results of Pd6Ni icosahedra.

    Table S1. ORR performance of icosahedral Pd6Ni/C NCs and state-of-the-art Pd-based NCs from recently published work.

    Table S2. ORR performance of icosahedral Pd6Ni/C NCs and state-of-the-art nonprecious metal catalysts from recently published work.

    Table S3. The relative energy of Ni-doped Pd (111) surface and the adsorption energy of oxygen atom on the Ni-doped Pd (111) surface.

    References (3854)

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. Lower-magnification TEM image, size distribution, and statistical results of the Pd6Ni icosahedra.
    • Fig. S2. HRTEM images, corresponding FFT images, and geometrical models of Pd6Ni icosahedra oriented along three typical projections.
    • Fig. S3. SEM-EDX and ICP-AES results of Pd3Ni icosahedra, Pd4Ni icosahedra, and Pd8Ni icosahedra.
    • Fig. S4. XRD patterns of Pd3Ni icosahedra, Pd4Ni icosahedra, and Pd8Ni icosahedra.
    • Fig. S5. HRTEM images of Pd3Ni icosahedra, Pd4Ni icosahedra, and Pd8Ni icosahedra.
    • Fig. S6. XPS spectra of Pd 3d and Ni 2p for PdxNi/C.
    • Fig. S7. TEM images of products under the typical condition but varying the amounts of Ni(HCO2)2·2H2O.
    • Fig. S8. TEM images of products under the typical condition but varying the amounts of AA.
    • Fig. S9. TEM images of products under the typical condition but changing the Ni(HCO2)2·2H2O to Ni(acac)2 and NiAc2.
    • Fig. S10. TEM images, SEM-EDX results, and PXRD patterns of Pd-Ni icosahedron intermediates.
    • Fig. S11. TEM images of Pd3Ni/C, Pd4Ni/C, Pd6Ni/C, and Pd8Ni/C.
    • Fig. S12. TEM images of the commercial Pd/C.
    • Fig. S13. CV curves of Pd-Ni/C, the commercial Pd/C, and the commercial Pt/C.
    • Fig. S14. TEM images and HRTEM images of Pd6Ni/C-400°C and Pd6Ni/C-500°C.
    • Fig. S15. ORR polarization curves for the commercial Pt/C, Pd6Ni/C, Pd6Ni/C-400°C, and Pd6Ni/C-500°C at different rotation rates.
    • Fig. S16. TEM images of the commercial Pt/C before and after ORR durability tests.
    • Fig. S17. TEM images and SEM-EDS patterns of Pd6Ni/C, Pd6Ni/C-400°C, and Pd6Ni/C-500°C after ORR durability tests.
    • Fig. S18. Detailed characterizations of Pd6Ni/C after ORR durability test.
    • Fig. S19. XPS spectra of Pd 3d and Ni 2p for the Pd6Ni/C before and after durability test.
    • Fig. S20. Surface valence bands of PdxNi/C.
    • Fig. S21. TEM images, image of ~50 ml of Pd6Ni icosahedra colloidal solution, and statistical results of Pd6Ni icosahedra.
    • Table S1. ORR performance of icosahedral Pd6Ni/C NCs and state-of-the-art Pd-based NCs from recently published work.
    • Table S2. ORR performance of icosahedral Pd6Ni/C NCs and state-of-the-art nonprecious metal catalysts from recently published work.
    • Table S3. The relative energy of Ni-doped Pd (111) surface and the adsorption energy of oxygen atom on the Ni-doped Pd (111) surface.
    • References (3854)

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