Qingyu Peng

Lightweight, Superelastic, and Mechanically Flexible Graphene/Polyimide Nanocomposite Foam for Strain Sensor Application.

The creation of superelastic, flexible three-dimensional (3D) graphene-based architectures is still a great challenge due to structure collapse or significant plastic deformation. Herein, we report a facile approach of transforming the mechanically fragile reduced graphene oxide (rGO) aerogel into superflexible 3D architectures by introducing water-soluble polyimide (PI). The rGO/PI nanocomposites are fabricated using strategies of freeze casting and thermal annealing. The resulting monoliths exhibit low density, excellent flexibility, superelasticity with high recovery rate, and extraordinary reversible compressibility. The synergistic effect between rGO and PI endows the elastomer with desirable electrical conductivity, remarkable compression sensitivity, and excellent durable stability. The rGO/PI nanocomposites show potential applications in multifunctional strain sensors under the deformations of compression, bending, stretching, and torsion.

Graphene Nanoribbon Aerogels Unzipped from Carbon Nanotube Sponges

Graphene nanoribbon aerogels are fabricated by directly unzipping multi-walled carbon nanotube sponges. These fascinating materials have potential applications as high performance nanocomposites and supercapacitor electrodes.

Super‐Stretchable Spring‐Like Carbon Nanotube Ropes

Spring-like carbon nanotube ropes consisting of perfectly arranged loops are fabricated by spinning single-walled nanotube films, and can sustain tensile strains as high as 285%.

Carbon nanotube-polypyrrole core-shell sponge and its application as highly compressible supercapacitor electrode

A carbon nanotube (CNT) sponge contains a three-dimensional conductive nanotube network, and can be used as a porous electrode for various energy devices. We present here a rational strategy to fabricate a unique CNT@polypyrrole (PPy) core-shell sponge, and demonstrate its application as a highly compressible supercapacitor electrode with high performance. A PPy layer with optimal thickness was coated uniformly on individual CNTs and inter-CNT contact points by electrochemical deposition and crosslinking of pyrrole monomers, resulting in a core-shell configuration. The PPy coating significantly improves specific capacitance of the CNT sponge to above 300 F/g, and simultaneously reinforces the porous structure to achieve better strength and fully elastic structural recovery after compression. The CNT@PPy sponge can sustain 1,000 compression cycles at a strain of 50% while maintaining a stable capacitance (> 90% of initial value). Our CNT@PPy core-shell sponges with a highly porous network structure may serve as compressible, robust electrodes for supercapacitors and many other energy devices.

Macroscopic, flexible, high-performance graphene ribbons.

Tailoring the structure and properties of graphene fibers is an important step toward practical applications. Here, we report macroscopic, long graphene ribbons formed by combining electrostatic interaction and shear stress during the wet-spinning process. The graphene ribbons are flexible and can be woven into complex structures, and the ribbon morphology can be tailored by controlling the orientation of wrinkles to obtain elasticity within a modest strain. We demonstrate several potential applications of pure or Pt-graphene hybrid ribbons as elastic strain sensors, counter electrodes for dye-sensitized fiber solar cells with cell efficiencies reaching 4.69% under standard illumination and 6.41% with a back reflector, and woven fabric supercapacitor electrodes. Our method can directly fabricate meter-long graphene ribbons with controlled structure and high performance as both energy conversion and energy storage materials.

Synthesis and characterization of a new hierarchical reinforcement by chemically grafting graphene oxide onto carbon fibers

We proposed a new hierarchical reinforcement consisting of graphene oxide (GO) and carbon fibers (CF). It was confirmed that GO was chemically grafted onto CF via poly(amido amine) dendrimers. The GO grafting significantly changes the surface configuration of CF. The new hierarchical reinforcement has the potential to be applied in high performance polymer matrix composites.

Overtwisted, Resolvable Carbon Nanotube Yarn Entanglement as Strain Sensors and Rotational Actuators

Introducing twists into carbon nanotube yarns could produce hierarchical architectures and extend their application areas. Here, we utilized such twists to produce elastic strain sensors over large strain (up to 500%) and rotation actuators with high energy density. We show that a helical nanotube yarn can be overtwisted into highly entangled, macroscopically random but locally organized structures, consisting of mostly double-helix segments intertwined together. Pulling the yarn ends completely resolved the entanglement in an elastic and reversible way, yielding large tensile strains with linear change in electrical resistance. Resolving an entangled yarn and releasing its twists could simultaneously rotate a heavy object (30 000 times the yarn weight) for more than 1000 cycles at high speed. The rotational actuation generated from a single entangled yarn produced energy densities up to 8.3 kJ/kg, and maintained similar capacity during repeated use. Our entangled CNT yarns represent a complex self-assembled system with applications as large-range strain sensors and robust rotational actuators.

Multifunctional graphene sheet–nanoribbon hybrid aerogels

Graphene sheets and nanoribbons are graphene-based nanostructures with different dimensions. Here, we show that these two materials can be combined to form highly porous, ultra-low density, compressible yet elastic aerogels, which can be used as efficient adsorbents and supercapacitor electrodes. The pore walls consist of stacked graphene sheets embedded with uniformly distributed thick nanoribbons unzipped from multi-walled carbon nanotubes as effective reinforcing skeletons. Owing to the large pore-size, robust and stable structure, and the nanoribbon-adhered pore walls, these hybrid aerogels show very large adsorption capacity for a series of organic solvents and oils (100 to 350 times of aerogel weight), and a specific capacitance of 256 F g−1 tested in a three-electrode electrochemical configuration, which is further improved to 537 F g−1 by depositing controlled loading pseudo-polymers into the aerogels. Our multifunctional graphene sheet–nanoribbon hybrid aerogels may find potential applications in many fields such as environmental cleanup and as flexible electrodes for energy storage systems such as supercapacitors and batteries.

Multifunctional Stiff Carbon Foam Derived from Bread

The creation of stiff yet multifunctional three-dimensional porous carbon architecture at very low cost is still challenging. In this work, lightweight and stiff carbon foam (CF) with adjustable pore structure was prepared by using flour as the basic element via a simple fermentation and carbonization process. The compressive strength of CF exhibits a high value of 3.6 MPa whereas its density is 0.29 g/cm(3) (compressive modulus can be 121 MPa). The electromagnetic interference (EMI) shielding effectiveness measurements (specific EMI shielding effectiveness can be 78.18 dB·cm(3)·g(-1)) indicate that CF can be used as lightweight, effective shielding material. Unlike ordinary foam structure materials, the low thermal conductivity (lowest is 0.06 W/m·K) with high resistance to fire makes CF a good candidate for commercial thermal insulation material. These results demonstrate a promising method to fabricate an economical, robust carbon material for applications in industry as well as topics regarding environmental protection and improvement of energy efficiency.

Multifunctional, Highly Flexible, Free-Standing 3D Polypyrrole Foam

Multifunctional, highly flexible 3D polypyrrole (PPy) foam is fabricated via a simple electrodeposition method by using nickel foam as the template. The 3D PPy foam has a unique interior structure and is robust enough to manipulate directly.