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.
First 1-step process for making seamless carbon-based nanomaterials that possess superior thermal, electrical and mechanical properties in 3 dimensions. It holds potential for increased energy storage in high efficiency batteries and supercapacitors, increasing the efficiency of energy conversion in solar cells, for lightweight thermal coatings and more.
In early testing, a 3D fiber-like supercapacitor made with the uninterrupted fibers of carbon nanotubes and graphene matched or bettered -by a factor of 4 -the reported record-high capacities for this type of device. Used as a counter electrode in a dye-sensitized solar cell, the material enabled the cell to convert power with up to 6.8% efficiency and more than doubled the performance of an identical cell that instead used an expensive platinum wire counter electrode.
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.]
“In our one-step process, the interface is made with C-C bonding so it looks as if it’s one single graphene sheet,” Dai said. “That makes it an excellent thermal and electrical conductor in all planes.”
METHOD: They etched radially aligned nanoholes along the length and circumference of a tiny aluminum wire, then used chemical vapor deposition to cover the surface with graphene using no metal catalyst that could remain in the structure. “Radially-aligned nanotubes grow in the holes. The graphene that sheathes the wire and nanotube arrays are covalently bonded, forming pure carbon-to-carbon nodal junctions that minimize thermal and electrical resistance,” Wang said.
Performance of the solid wire supercapacitors of 3D graphene-CNT fiber for energy storage.
Using the Brunauer, Emmett and Teller theory, they calculate the surface area to be nearly 527 sq m/g of material. Testing showed the material makes an ideal electrode for highly efficient energy storage. Capacitance by area reached as high as 89.4 millifarads / sq cm and by length, up to 23.9 millifarads/cm in the fiber-like supercapacitor.
The properties can be customized ie very long, or into a tube with a wider or narrower diameter, and the density of nanotubes can be varied to produce materials with differing properties for different needs.
APPS: Nanomaterial charge storage in capacitors and batteries or the large surface could enable storage of hydrogen + wider applications, including sensitive sensors, wearable electronics, thermal management and multifunctional aerospace systems.
http://dx.doi.org/10.1126/sciadv.1400198
http://www.eurekalert.org/pub_releases/2015-09/cwru-nnm090415.php
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