Research ArticleELECTRICAL ENGINEERING

Rationally designed graphene-nanotube 3D architectures with a seamless nodal junction for efficient energy conversion and storage

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Science Advances  04 Sep 2015:
Vol. 1, no. 8, e1400198
DOI: 10.1126/sciadv.1400198
  • Fig. 1 Schematic diagrams showing the synthesis and microstructures of a 3D graphene-RACNT fiber.

    (A) Aluminum wire. (B) Surface anodized aluminum wire (AAO wire). (C) 3D graphene-RACNT structure on the AAO wire. (D) Schematic representation of the pure 3D graphene-RACNT structure. (E to G) Top view SEM images of the 3D graphene-RACNT fiber at different magnifications. (I to K) SEM images of the cross-section of the 3D graphene-RACNT fiber. (H and L) AFM images of the 3D graphene-RACNT fiber. (M to P) SEM image (M) and corresponding EDX elemental mapping of (N) aluminum, (O) oxygen, and (P) carbon from the 3D graphene-RACNT fiber.

  • Fig. 2 Microscopy characterization of the 3D graphene-RACNT structures.

    (A and B) Graphene sheet connecting to the open tips of RACNTs. (C) Closed end of RACNTs. (D) Schematic representation of the 3D graphene-RACNT network; inset shows the energy-minimized structure from MD simulations (Supplementary Materials). (E) Broken graphene sheet from the 3D graphene-RACNT network. (F) TEM image of the side view of the 3D graphene-RACNT around the graphene-nanotube interface. (G and H) Cross-section view of the constituent RACNTs within the 3D graphene-RACNT structure (G) and corresponding carbon mapping (H). (I) Circle-shaped 3D graphene-RACNT fiber. (J) Piece of weaved graphene-RACNT fibers. (K) SEM image of a knot of the graphene-RACNT fiber. (L) Photograph of a 2-m-long graphene-RACNT fiber rolled on a long stick. [The diameter of the graphene-RACNT fibers in (I) to (L) is 100 μm.]

  • Fig. 3 Performance of the solid wire supercapacitors of 3D graphene-CNT fiber for energy storage.

    (A and B) SEM images of the top and cross-section of the solid-state wire supercapacitor based on the 3D graphene-RACNT fiber electrodes (the diameter of the fiber is 100 μm). (C) CV curves of the solid-state wire supercapacitor based on the 3D graphene-RACNT wire electrodes at scanning rates from 100 to 500 mV/s. (D) Galvanostatic charge and discharge curves of the 3D graphene-RACNT wire capacitor at different currents. (E) Surface-specific capacitance of the 3D graphene-RACNT wire electrode calculated from the galvanostatic charge/discharge curves. (F to L) Integrated solid wire supercapacitors either in series or in parallel (the diameter of the fibers used in integrated devices is 380 μm). (F) Schematic representation of an integrated supercapacitor in series from three graphene-RACNT wire supercapacitors. (G and H) Galvanostatic charge-discharge curves and CV curves, respectively, for the series integrated graphene-RACNT wire supercapacitor and a single wire supercapacitor. (I) Use of an integrated supercapacitor to light up a commercial LED. (J) Schematic representation of an integrated supercapacitor in parallel from three graphene-RACNT wire supercapacitors. (K and L) Galvanostatic charge-discharge curves and CV curves, respectively, for the parallel integrated graphene-RACNT wire supercapacitor and a single wire supercapacitor.

  • Fig. 4 3D graphene-RACNT fiber as the counter electrode for wire-shaped DSSCs.

    (A) Schematic representation of wire-shaped DSSC using 3D graphene-CNT fiber as the counter electrode and the TiO2 nanotube fiber as the photo anode. (B) Schematic drawing for the cross-section view of the wire-shaped DSSC. (C) SEM image of the cross-section view of the wire-shaped DSSC. (D) Photograph of the wire-shaped DSSC sealed in a glass capillary tube. (E) Flexible wire-shaped DSSC sealed in a transparent FET plastic tube. (F) Knot made from the flexible DSSC. (G) Current density–voltage characteristics of DSSCs with graphene wire, CNT wire, Pt wire, or 3D graphene-RACNT fiber as the counter electrode. (H) Nyquist plots of the 3D graphene-CNT fiber and the Pt wire measured in the I/I3 electrolyte (10 mM LiI + 1 mM I2 + 0.1 M LiClO4 + acetonitrile). (I) Current density–voltage characteristics of DSSCs with the 3D graphene-RACNT wire counter electrode before and after bending.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/1/8/e1400198/DC1

    Fig. S1. Photographs of aluminum wire, AAO wire, and 3D graphene-RACNT deposited on the AAO wire.

    Fig. S2. SEM images of the cross-section view of the 3D graphene-RACNT fiber after the removal of the aluminum and AAO template under different magnifications.

    Fig. S3. TEM image of the edge of the 3D graphene-RACNT fiber with different magnifications.

    Fig. S4. Top view TEM images of the center of the 3D graphene-RACNT fiber with different magnifications.

    Fig. S5. TEM images of the side of the 3D graphene-RACNT fiber rotated with different angles from −19° to 30° around the red arrow.

    Fig. S6. TEM images of an individual carbon nanotube from the 3D graphene-RACNT fiber under different magnifications.

    Fig. S7. Raman spectrum of the 3D graphene-RACNT fiber on the AAO wire.

    Fig. S8. The XPS survey spectrum of the 3D graphene-RACNT fiber, and the corresponding high-resolution XPS C1s spectrum.

    Fig. S9. The resistance of the as-prepared 3D graphene-RACNT wire.

    Fig. S10. CV curves and galvanostatic discharge curves of the 3D graphene-RACNT wire (0.1 mm in diameter) electrode in 1 M H2SO4 solution.

    Fig. S11. SEM images of the 3D graphene-RACNT wire (100 μm in diameter) with different shell thicknesses via anodizing at different times.

    Fig. S12. CV curves of the fiber-100μm-2hrs, fiber-100μm-4hrs, and fiber-100μm-12hrs in 5 mM K3Fe(CN)6/0.1 M KCl solution.

    Fig. S13. CV curves, galvanostatic charge and discharge curves, and the surface specific capacitance of the 3D graphene-RACNT wire electrodes (fiber-100μm-2hrs, fiber-100μm-4hrs, and fiber-100μm-12hrs).

    Fig. S14. Photographs of the 3D graphene-RACNT fibers prepared from aluminum wire with different diameters.

    Fig. S15. SEM images of the 3D graphene-RACNT fibers prepared from aluminum wires with different diameters.

    Fig. S16. CV curves and Nyquist plots of the 3D graphene-RACNT fibers with a diameter.

    Fig. S17. CV curves of the solid-sate wire supercapacitor at high scanning rates, and galvanostatic charge and discharge curves of the 3D graphene-VACNT wire capacitor at high current density.

    Fig. S18. Photograph, CV curves, galvanostatic charge and discharge curves, and the surface specific capacitance and length specific capacitance of the solid-state wire supercapacitor based on the 3D graphene-RACNT fiber electrodes (810 mm in diameter).

    Fig. S19. The long term stability and bending stability tests for the supercapacitor based on the 3D graphene-RACNT electrodes with diameter of 100 μm.

    Fig. S20. Photographs, CV curves, and galvanostatic charge/discharge curves of the 3D graphene-RACNT wire supercapacitor before and after rolling on a glass tube.

    Fig. S21. Photographs of graphene-RACNT wire supercapacitor weaved into a piece of fabric and rolling over a stick, and its CV curves and galvanostatic charge/discharge curves before and after rolling on a stick.

    Fig. S22. SEM images of TiO2 nanotube/Ti wire.

    Fig. S23. SEM images of a 3D graphene-RACNT flexible wire DSSC before and after bend.

    Fig. S24. Schematics of Al2O3 template with a filleted hole in the center, and MD model of the template.

    Fig. S25. Schematics of CNT-graphene junction.

    Fig. S26. Side view and cross section of three-layered CNT-graphene junctions with 135° fillet and without fillet.

    Fig. S27. Normalized bending energy predicted by the analytical model, and normalized potential energy calculated by MD as a function of the fillet angles.

    Table S1. The reported areal capacitance and length capacitance of the fiber supercapacitor in references.

    Table S2. Jsc, Voc, FF, and power conversion efficiency for wire-shaped DSSCs with the 3D graphene-CNT fiber, and Pt wire as the counter electrode.

    Table S3. Electroactive surface areas of the 3D graphene-RACNT fiber electrodes.

    Table S4. Series resistance of the 3D graphene-RACNT fiber electrodes.

    Table S5. Jsc, Voc, FF, and power conversion efficiency for wire-shaped DSSCs with the 3D graphene-CNT fiber before and after bend.

    Movie S1. A movie made from those consequent TEM images, showing the seamless 3D junction structure between the CNTs and the graphene sheet.

    Movie S2. A movie made from those consequent TEM images, revealing the aligned CNT bundles (see text) and their seamless junction with the graphene sheet.

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. Photographs of aluminum wire, AAO wire, and 3D graphene-RACNT deposited on the AAO wire.
    • Fig. S2. SEM images of the cross-section view of the 3D graphene-RACNT fiber after the removal of the aluminum and AAO template under different magnifications.
    • Fig. S3. TEM image of the edge of the 3D graphene-RACNT fiber with different magnifications.
    • Fig. S4. Top view TEM images of the center of the 3D graphene-RACNT fiber with different magnifications.
    • Fig. S5. TEM images of the side of the 3D graphene-RACNT fiber rotated with different angles from −19° to 30° around the red arrow.
    • Fig. S6. TEM images of an individual carbon nanotube from the 3D graphene-RACNT fiber under different magnifications.
    • Fig. S7. Raman spectrum of the 3D graphene-RACNT fiber on the AAO wire.
    • Fig. S8. The XPS survey spectrum of the 3D graphene-RACNT fiber, and the corresponding high-resolution XPS C1s spectrum.
    • Fig. S9. The resistance of the as-prepared 3D graphene-RACNT wire.
    • Fig. S10. CV curves and galvanostatic discharge curves of the 3D graphene-RACNT wire (0.1 mm in diameter) electrode in 1 M H2SO4 solution.
    • Fig. S11. SEM images of the 3D graphene-RACNT wire (100μm in diameter) with different shell thicknesses via anodizing at different times.
    • Fig. S12. CV curves of the fiber-100μm-2hrs, fiber-100μm-4hrs, and fiber-100μm-12hrs in 5 mM K3Fe(CN)6/0.1 M KCl solution.
    • Fig. S13. CV curves, galvanostatic charge and discharge curves, and the surface specific capacitance of the 3D graphene-RACNT wire electrodes (fiber-100μm-2hrs, fiber-100μm-4hrs, and fiber-100μm-12hrs).
    • Fig. S14. Photographs of the 3D graphene-RACNT fibers prepared from aluminum wire with different diameters.
    • Fig. S15. SEM images of the 3D graphene-RACNT fibers prepared from aluminum wires with different diameters.
    • Fig. S16. CV curves and Nyquist plots of the 3D graphene-RACNT fibers with a diameter.
    • Fig. S17. CV curves of the solid-sate wire supercapacitor at high scanning rates, and galvanostatic charge and discharge curves of the 3D graphene-VACNT wire capacitor at high current density.
    • Fig. S18. Photograph, CV curves, galvanostatic charge and discharge curves, and the surface specific capacitance and length specific capacitance of the solid-state wire supercapacitor based on the 3D graphene-RACNT fiber electrodes (810 mm in diameter).
    • Fig. S19. The long term stability and bending stability tests for the supercapacitor based on the 3D graphene-RACNT electrodes with diameter of 100μm.
    • Fig. S20. Photographs, CV curves, and galvanostatic charge/discharge curves of the 3D graphene-RACNT wire supercapacitor before and after rolling on a glass tube.
    • Fig. S21. Photographs of graphene-RACNT wire supercapacitor weaved into a piece of fabric and rolling over a stick, and its CV curves and galvanostatic charge/discharge curves before and after rolling on a stick.
    • Fig. S22. SEM images of TiO2 nanotube/Ti wire.
    • Fig. S23. SEM images of a 3D graphene-RACNT flexible wire DSSC before and after bend.
    • Fig. S24. Schematics of Al2O3 template with a filleted hole in the center, and MD model of the template.
    • Fig. S25. Schematics of CNT-graphene junction.
    • Fig. S26. Side view and cross section of three-layered CNT-graphene junctions with 135° fillet and without fillet.
    • Fig. S27. Normalized bending energy predicted by the analytical model, and normalized potential energy calculated by MD as a function of the fillet angles.
    • Table S1. The reported areal capacitance and length capacitance of the fiber supercapacitor in references.
    • Table S2. Jsc, Voc, FF, and power conversion efficiency for wire-shaped DSSCs with the 3D graphene-CNT fiber, and Pt wire as the counter electrode.
    • Table S3. Electroactive surface areas of the 3D graphene-RACNT fiber electrodes.
    • Table S4. Series resistance of the 3D graphene-RACNT fiber electrodes. Table S5. Jsc, Voc, FF, and power conversion efficiency for wire-shaped DSSCs with the 3D graphene-CNT fiber before and after bend.

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    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.avi format). A movie made from those consequent TEM images, showing the seamless 3D junction structure between the CNTs and the graphene sheet.
    • Movie S2 (.avi format). A movie made from those consequent TEM images, revealing the aligned CNT bundles (see text) and their seamless junction with the graphene sheet.

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