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Edge-selenated graphene nanoplatelets as durable metal-free catalysts for iodine reduction reaction in dye-sensitized solar cells

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Science Advances  17 Jun 2016:
Vol. 2, no. 6, e1501459
DOI: 10.1126/sciadv.1501459
  • Fig. 1 Structural identification of SeGnPs.

    (A) Proposed atomic model of SeGnPs. (B) AR-TEM image obtained at the edge of SeGnPs. (C and D) Magnified AR-TEM images. (E and F) Corresponding inverse fast Fourier transform (IFFT) images of a graphene edge with armchair and zigzag configurations, respectively.

  • Fig. 2 Comparison between conventional Pt and SeGnP electrodes.

    (A and B) Nyquist plots of the Pt-CEs and SeGnP-CEs: Co(bpy)32+/3+ (A) and I/I3 (B). The inset in (A) is an enlargement of the EIS spectrum of the SeGnP-CEs in high-frequency range. (C and D) Normalized Rct and ct changes versus the EIS scan number: Co(bpy)32+/3+ (C) and I/I3 (D).

  • Fig. 3 Theoretical calculation and proposed mechanism of IRR.

    (A) For the representative single-coordinated, double-coordinated, and hydrogenated Se [Se(c1), Se(c2), and SeH, respectively]–doped armchair (ac) and zigzag (zz) graphene edges (top panel), the adsorption energies of the I atom explicitly solvated by acetonitrile molecules were evaluated and compared with the undoped edge and basal plane cases (bottom panel). The Pt(111) value of 0.52 eV has been taken from the study of Li et al. (24). In the bottom panel, the shaded region indicates the IRR activity criterion. (B) For various I- and I3-adsorbed graphene basal plane models (top panel and figs. S27 and S28), the current-voltage (I-V) curves were calculated and compared with those from pristine graphene (bottom panel). In the top panel, Mulliken charge populations were coded into atomic structures. (C) IRR mimetic diagram on the SeGnP surface. (D) Nyquist plots of SeGnP-CEs and their EC at room temperature.

  • Fig. 4 DSSC performance of Pt-CEs and SeGnP-CEs.

    (A) J-V characteristics of the DSSCs with SM315/Co(bpy)32+/3+ and N719/I/I3. (B) Rct of the same DSSCs.

  • Table 1 EIS parameters of symmetrical dummy cells with Pt and SeGnP electrodes.

    Rs, serial resistance; Rct, charge-transfer resistance; Cdl, double-layer capacitance; Rtm, transmission resistance; Cad, capacitance due to the adsorption of I/I3 on the graphitic basal plane; J0, exchange current density.

    CEElectrolyteRs (ohm⋅cm2)Rct (ohm⋅cm2)Cdl (μF cm2)Rtm (ohm⋅cm2)Cad (μF cm2)J0 (mA cm−2)
    PtCo(bpy)32+/3+3.121.858.8813.9
    SeGnPs3.200.1317.5234
    PtI/I33.420.616.0221.1
    SeGnPs2.920.231330.1712.432.1
  • Table 2 Photovoltaic performance of Pt-DSSCs and SeGnP-DSSCs with different electrolytes.

    Jsc, short-circuit current density; Voc, open-circuit voltage.

    CEDyeElectrolyteJsc (mA mA−2)Voc (mV)FF (%)PCE (%)
    PtSM315Co(bpy)32+/3+15.30 ± 0.36863 ± 2.076.6 ± 0.410.11 ± 0.25
    SeGnPs16.27 ± 0.03876 ± 6.577.0 ± 1.410.98 ± 0.17
    PtN719I/I317.26 ± 0.32729 ± 6.872.2 ± 1.19.07 ± 0.20
    SeGnPs18.16 ± 0.44692 ± 2.973.1 ± 1.39.17 ± 0.04

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/2/6/e1501459/DC1

    Supplementary Materials and Methods

    fig. S1. Schematic representation of mechanochemical ball milling.

    fig. S2. Field-emission SEM images and element mappings of SeGnPs.

    fig. S3. Dark-field TEM image and element mappings with EDX (TEM) spectra.

    fig. S4. EDX (SEM) and XPS spectra.

    fig. S5. Nitrogen adsorption-desorption isotherms, Raman spectra, XRD patterns, and contact angles.

    fig. S6. TGA thermograms.

    fig. S7. Photographs of SeGnP dispersed solutions in various solvents.

    fig. S8. AR-TEM, HR-TEM, and STEM images.

    fig. S9. SEM images of SeGnP coated on FTO.

    fig. S10. Schematic representation of symmetrical dummy cell and EC.

    fig. S11. Electrocatalytic activities of the HGnP dummy cell in Co(bpy)32+/3+ electrolytes.

    fig. S12. Electrocatalytic activities of the reference HGnP dummy cell in I/I3 electrolytes.

    fig. S13. EC model.

    fig. S14. Optical transmittance, SEM images, and Nyquist plots.

    fig. S15. Nyquist plots and resistance changes.

    fig. S16. Potential step CA curves on symmetrical dummy cells.

    fig. S17. Cyclic voltammograms in Co(bpy)32+/3+ redox couple and oxidation and reduction peak.

    fig. S18. Cyclic voltammograms in I/I3 redox couple and oxidation and reduction peak.

    fig. S19. Cyclic voltammograms obtained at a scan rate of 50 mV s−1.

    fig. S20. Nyquist plots of the symmetrical dummy cells on Co(bpy)32+/3+ and I/I3 electrolytes.

    fig. S21. Nyquist plots measured 1 month later after 1000 cycling measurements.

    fig. S22. Se-doped graphene models.

    fig. S23. Adsorption geometries of the I atom on Se(c1)-GnP in vacuum and acetonitrile.

    fig. S24. Se-doped models and the adsorption energies of the I atom.

    fig. S25. Graphene models used in DFT and computational setup for NEGF.

    fig. S26. Configurations of I or I3 adsorbed on graphene.

    fig. S27. Mulliken charge populations.

    fig. S28. Transmission functions of graphene and corresponding I-V characteristics.

    fig. S29. Nyquist plots and Rct and J0 as temperature.

    fig. S30. Photocurrent transient dynamics and Nyquist plots of DSSCs.

    table S1. TGA, EA, EDX, and XPS data of the pristine graphite and SeGnPs.

    table S2. BET surface area, pore volume, and pore size of the pristine graphite and SeGnPs.

    table S3. The size of I3 and Co(bpy)33+ ions.

    References (4168)

  • Supplementary Materials

    This PDF file includes:

    • Supplementary Materials and Methods
    • fig. S1. Schematic representation of mechanochemical ball milling.
    • fig. S2. Field-emission SEM images and element mappings of SeGnPs.
    • fig. S3. Dark-field TEM image and element mappings with EDX (TEM) spectra.
    • fig. S4. EDX (SEM) and XPS spectra.
    • fig. S5. Nitrogen adsorption-desorption isotherms, Raman spectra, XRD patterns, and contact angles.
    • fig. S6. TGA thermograms.
    • fig. S7. Photographs of SeGnP dispersed solutions in various solvents.
    • fig. S8. AR-TEM, HR-TEM, and STEM images.
    • fig. S9. SEM images of SeGnP coated on FTO.
    • fig. S10. Schematic representation of symmetrical dummy cell and EC.
    • fig. S11. Electrocatalytic activities of the HGnP dummy cell in Co(bpy)32+/3+ electrolytes.
    • fig. S12. Electrocatalytic activities of the reference HGnP dummy cell in I/I3 electrolytes.
    • fig. S13. EC model.
    • fig. S14. Optical transmittance, SEM images, and Nyquist plots.
    • fig. S15. Nyquist plots and resistance changes.
    • fig. S16. Potential step CA curves on symmetrical dummy cells.
    • fig. S17. Cyclic voltammograms in Co(bpy)32+/3+ redox couple and oxidation and reduction peak.
    • fig. S18. Cyclic voltammograms in I/I3 redox couple and oxidation and reduction peak.
    • fig. S19. Cyclic voltammograms obtained at a scan rate of 50 mV s−1.
    • fig. S20. Nyquist plots of the symmetrical dummy cells on Co(bpy)32+/3+ and I/I3 electrolytes.
    • fig. S21. Nyquist plots measured 1 month later after 1000 cycling measurements.
    • fig. S22. Se-doped graphene models.
    • fig. S23. Adsorption geometries of the I atom on Se(c1)-GnP in vacuum and acetonitrile.
    • fig. S24. Se-doped models and the adsorption energies of the I atom.
    • fig. S25. Graphene models used in DFT and computational setup for NEGF.
    • fig. S26. Configurations of I or I3 adsorbed on graphene.
    • fig. S27. Mulliken charge populations.
    • fig. S28. Transmission functions of graphene and corresponding I-V characteristics.
    • fig. S29. Nyquist plots and Rct and J0 as temperature.
    • fig. S30. Photocurrent transient dynamics and Nyquist plots of DSSCs.
    • table S1. TGA, EA, EDX, and XPS data of the pristine graphite and SeGnPs.
    • table S2. BET surface area, pore volume, and pore size of the pristine graphite and SeGnPs.
    • table S3. The size of I3 and Co(bpy)33+ ions.
    • References (41–68)

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