Kaixuan Sheng

Self-Assembled Graphene Hydrogel via a One-Step Hydrothermal Process

Self-assembly of two-dimensional graphene sheets is an important strategy for producing macroscopic graphene architectures for practical applications, such as thin films and layered paperlike materials. However, construction of graphene self-assembled macrostructures with three-dimensional networks has never been realized. In this paper, we prepared a self-assembled graphene hydrogel (SGH) via a convenient one-step hydrothermal method. The SGH is electrically conductive, mechanically strong, and thermally stable and exhibits a high specific capacitance. The high-performance SGH with inherent biocompatibility of carbon materials is attractive in the fields of biotechnology and electrochemistry, such as drug-delivery, tissue scaffolds, bionic nanocomposites, and supercapacitors.

Ultrahigh-rate supercapacitors based on eletrochemically reduced graphene oxide for ac line-filtering.

The recent boom in multifunction portable electronic equipments requires the development of compact and miniaturized electronic circuits with high efficiencies, low costs and long lasting time. For the operation of most line-powered electronics, alternating current (ac) line-filters are used to attenuate the leftover ac ripples on direct current (dc) voltage busses. Today, aluminum electrolytic capacitors (AECs) are widely applied for this purpose. However, they are usually the largest components in electronic circuits. Replacing AECs by more compact capacitors will have an immense impact on future electronic devices. Here, we report a double-layer capacitor based on three-dimensional (3D) interpenetrating graphene electrodes fabricated by electrochemical reduction of graphene oxide (ErGO-DLC). At 120-hertz, the ErGO-DLC exhibited a phase angle of −84 degrees, a specific capacitance of 283 microfaradays per centimeter square and a resistor-capacitor (RC) time constant of 1.35 milliseconds, making it capable of replacing AECs for the application of 120-hertz filtering.

Graphene Hydrogels Deposited in Nickel Foams for High‐Rate Electrochemical Capacitors

Graphene hydrogel/nickel foam composite electrodes for high-rate electrochemical capacitors are produced by reduction of an aqueous dispersion of graphene oxide in a nickel foam (upper half of figure). The micropores of the hydrogel are exposed to the electrolyte so that ions can enter and form electrochemical double-layers. The nickel framework shortens the distances of charge transfer. Therefore, the electrochemical capacitor exhibits highrate performance (see plots).

High-performance self-assembled graphene hydrogels prepared by chemical reduction of graphene oxide

Abstract Three-dimensional self-assembled graphene hydrogels (SGHs) have been fabricated by chemical reduction of graphene oxide (GO) with sodium ascorbate. The SGHs were characterized by scanning electron microscopy, rheological tests, electrical conductivity measurements, X-ray photoelectron spectroscopy, X-ray diffraction, and Raman spectroscopy. Results indicate that the reduction of GO promotes the assembly of graphene sheets. The SGHs are electrically conductive (1 S·m −1 ) and mechanically strong and exhibit excellent electrochemical performance. In 1 mol·L −1 aqueous solution of H 2 SO 4 , the specific capacitance of SGHs was measured to be about 240 F·g −1 at a discharge current density of 1.2 A·g −1 .

Graphene oxide/conducting polymer composite hydrogels

Graphene oxide/conducting polymer (GO/CP) composite hydrogels were prepared by in situ chemical polymerization of corresponding aromatic monomers in aqueous dispersions of GO sheets. GO/polypyrrole (PPy), GO/poly(3,4-ethylenedioxythiophene) (PEDOT) and GO/polyaniline (PANi) hydrogels were obtained by this technique, and the mechanism of gelation was discussed. Among them, GO/PPy composite hydrogels were tested to have low critical hydrogel concentrations ( 10 kPa) and electrical conductivity, and strong electrochemical activity. A gas sensor based on a typical GO/PPy hydrogel showed high sensitivity towards ammonia gas.

Solution-processable graphene nanomeshes with controlled pore structures

Graphene nanomeshes (GNMs) which can be cheaply produced on a large scale and processed through wet approaches are important materials for various applications, including catalysis, composites, sensors and energy related systems. Here, we report a method for large scale preparation of GNMs by refluxing reduced graphene oxide sheets in concentrated nitric acid solution (e.g., 8 moles per liter). The diameters of nanopores in GNM sheets can be readily modulated from several to hundreds nanometers by varying the time of acid treatment. The porous structure increased the specific surface areas of GNMs and the transmittances of GNM-based thin films. Furthermore, GNMs have large number of carboxyl groups at the edges of their nanopores, leading to good dispersibility in aqueous media and strong peroxidase-like catalytic activity.