Han Hu

Ultralight and Highly Compressible Graphene Aerogels

Chemically converted graphene aerogels with ultralight density and high compressibility are prepared by diamine-mediated functionalization and assembly, followed by microwave irradiation. The resulting graphene aerogels with density as low as 3 mg cm(-3) show excellent resilience and can completely recover after more than 90% compression. The ultralight graphene aerogels possessing high elasticity are promising as compliant and energy-absorbing materials.

Self-Sensing, Ultralight, and Conductive 3D Graphene/Iron Oxide Aerogel Elastomer Deformable in a Magnetic Field

Three-dimensional (3D) graphene aerogels (GA) show promise for applications in supercapacitors, electrode materials, gas sensors, and oil absorption due to their high porosity, mechanical strength, and electrical conductivity. However, the control, actuation, and response properties of graphene aerogels have not been well studied. In this paper, we synthesized 3D graphene aerogels decorated with Fe3O4 nanoparticles (Fe3O4/GA) by self-assembly of graphene with simultaneous decoration by Fe3O4 nanoparticles using a modified hydrothermal reduction process. The aerogels exhibit up to 52% reversible magnetic field-induced strain and strain-dependent electrical resistance that can be used to monitor the degree of compression/stretching of the material. The density of Fe3O4/GA is only about 5.8 mg cm(-3), making it an ultralight magnetic elastomer with potential applications in self-sensing soft actuators, microsensors, microswitches, and environmental remediation.

Highly Stretchable and Ultrasensitive Strain Sensor Based on Reduced Graphene Oxide Microtubes-Elastomer Composite.

Strain sensors with excellent flexibility, stretchability, and sensitivity have attracted increasing interests. In this paper, a highly stretchable and ultrasensitive strain sensor based on reduced graphene oxide microtubes-elastomer is fabricated by a template induced assembly and followed a polymer coating process. The sensors can be stretched in excess of 50% of its original length, showing long-term durability and excellent selectivity to a specific strain under various disturbances. The sensitivity of this sensor is as high as 630 of gauge factor under 21.3% applied strain; more importantly, it can be easily modulated to accommodate diverse requirements. Implementation of the device for gauging muscle-induced strain in several biological systems shows reproducibility and different responses in the form of resistance or current change. The developed strain sensors show great application potential in fields of biomechanical systems, communications, and other related areas.

Naturally Dried Graphene Aerogels with Superelasticity and Tunable Poisson's Ratio.

A novel natural drying (ND) strategy for low-cost and simple fabrication of graphene aerogels (GAs) is highlighted. The as-formed NDGAs exhibit ultralarge reversible compressibility (99%) and tunable Poissons ratio behaviors (-0.30 < ν < 0.46), which suggests promising applications in soft actuators, soft robots, sensors, deformable electronic devices, drug release, thermal insulator, and protective materials.

Low temperature plasma-mediated synthesis of graphene nanosheets for supercapacitor electrodes

Controllable production of graphene by simultaneously exfoliating and reducing graphite oxide (GO) under dielectric barrier discharge (DBD) plasma with various working gases, including H2 (reducing), Ar (inert) and CO2 (oxidizing), has been investigated. The deoxygenation level of GO is related to the type of working gases while regardless of the bulk temperature during plasma discharge, which implicates a high-energy electron/ion bombardment deoxygenation mechanism. Acting as electrode materials in a supercapacitor cell with KOH electrolyte, graphene nanosheets (GS) from various plasmas exhibit high specific capacitance and good electrochemical stability. With the assistance of low temperature plasma, this approach has the potential to enable the fabrication of a broad spectrum of graphene-based composites that are sensitive to high temperatures.

Polymer casting of ultralight graphene aerogels for the production of conductive nanocomposites with low filling content

We report a convenient and effective method to fabricate monolithic and conductive nanocomposites with various morphologies by directly infiltrating epoxy resin into the pores of ultralight graphene aerogels (ULGAs) with desired morphologies, followed by curing. These composites show linear ohmic behavior even with graphene filling content as low as 0.28 wt%. The electrical conductivity of the composites can be modulated in the range from 3.3 × 10−2 to 4.8 × 10−1 S m−1, superior to that of traditional composites by directly mixing the powdery graphene with the polymer. Furthermore, the conductivity of the nanocomposites remains unchanged in a wide range of temperature which may allow the structures to be promising candidates as resistance elements for integrated circuits (ICs).

Supramolecular polymerization-assisted synthesis of nitrogen and sulfur dual-doped porous graphene networks from petroleum coke as efficient metal-free electrocatalysts for the oxygen reduction reaction

Efficient metal-free carbon electrocatalysts for the oxygen reduction reaction (ORR) represent a promising alternative to the scarce and costly noble metal-based counterparts, and their performance is good enough to fulfill the requirements of real-life applications. Herein, we describe the rational design and synthesis of nitrogen/sulfur-codoped porous graphene networks (N,S-PGN) as a highly efficient ORR catalyst. Assisted by supramolecular polymerization, petroleum coke, a byproduct produced by the oil refinery industry in million tons every year, can be converted into N/S-codoped graphene nanosheets with a highly porous architecture. Such a hierarchical and doped structure favors the exposure of the active sites and facilitates electron transport. As a result, N,S-PGN exhibits a remarkable electrocatalytic activity for the ORR and, in particular, outperforms the Pt/C electrode in terms of a superior diffusion-limiting current density and stability when operated under the same conditions. Furthermore, the increased number of carbon active sites and enhanced electron transport were confirmed by theoretical calculations. It was found that codoping porous graphene increases the charge density on the carbon active sites and increases the HOMO energy, thus favoring the ORR. The present study demonstrates a novel and feasible route for preparing heteroatom-codoped porous graphene for energy applications as well as a new strategy for the value-added utilization of petroleum coke.

In Situ Growth of Carbon Nanotubes on Carbon Foam for Enhanced Oil Adsorption

This work presents a facile approach to grow carbon nanotubes (CNTs) on the surface of carbon foams (CFs) for the fabrication of hierarchical CNTs/CF composites, which exhibit enhanced oil adsorption capability. The preparation of CFs is carried out by using commercially available polyurethane (PU) foams as hard template and resol as carbon precursor. Fe/Mg/Al layered double hydroxide (LDHs) is used as catalyst precursor for the efficient growth of CNTs on CFs via chemical vapor deposition (CVD), in which CNTs are controllably grown onto the strut of CFs. The presence of CNTs in the CFs can significantly improve the hydrophobicity of the composites and enable the selective separation of oil from water with the combination of hydrophobicity and capillary action. Such well-designed hierarchical nanostructures are benefit for maximum utilization of cell structure and surface property of the composites and display good oil adsorption performance. The synthesis procedure paves the way for the exploitation of the CFs as adsorbent for the removal of spill oil and environmental protection.