Preparation And Applications Of Three Dimensional Graphene Composites

As an excellent two-dimensional carbon nanomaterial, graphene and its composites become a hot spot of material science nowadays. Three-dimensional graphene is a new kind of graphene derived material and it has been widely studied in recent years. It can not only keep unique properties of two-dimensional structure, but also obtain large surface area and controlled porous structure by integrating graphene into three-dimensional macroscopic structure. It is quite attractive to prepare multifunctional three-dimensional graphene composites with wide applications in catalysis, sensors, energy storage, environment and electronic devices. In this work, graphite oxide was prepared by a modified Hummers method firstly. Ultrasonic with water for 1 h, the graphene oxide precursor was successfully obtained. Chemical reduction assembly method and template method were used to prepare two kinds of 3DG composites, respectively. Their applications in adsorption, oil-water separation and supercapacitor were explored. The details of experiments are described as follows:A 3D graphene hydrogel(TA-GH) was successfully prepared by chemical reduction assembly method under the atmospheric pressure using bio-based material named tannic acid(TA) as the reducing agent. GO was reduced into reduced graphene oxide(rGO) by TA at 90 ℃, which then assembled into a hydrogel with good structure stability driven by Van der Waals force, hydrophobic effect and π-π interactions. A light-weight, conductive and hydrophobic 3D graphene aerogel(TA-GA) was thus obtained via a freeze-drying process. The preparation conditions, such as reaction time, reaction temperature, TA: GO mass ratio and the concentration of GO, have great influence on the macroscopic structure of TA-GH. The TA-GA shows a porous structure shown from SEM images, and its BET surface area is as high as 136 m2/g. TA-GA also demonstrated good mechanical property which could bear a weight about 15500 times of its own. The applications of the obtained three dimentional graphene composite in dye adsorption and oil-water separation were explored. TA-GH has a good adsorption performance of dye, and its adsorption capacity for rhodamine B is as high as 378 mg/g. The TA-GA shows a good adsorbing effect for some organic solvents and vegetable oils, and its adsorption capacities for chloroform and soybean oil are as high as 20.6 and 23.8 g/g, respectively. More over, the TA-GA has a fast adsorption toward various oil and possessed recycled oil-water separation ability towards organic solvents.A three dimentional graphene/polypyrrole foam electrode(rGO/PPy-NF) with a specific macrostructure was prepared using nickel foam(NF) as template. GO was reduced into rGO under a certain voltage, and deposited onto the NF surface in a typical electrochemical deposition process. The subsequent electrochemical polymerization process of pyrrole(Py) led to the successful fabrication of three dimentional rGO/PPy foam electrodes(rGO/PPy-NF). The rGO/PPy-NF has the advantages of the porous structure of NF, the good electrical conductivity of rGO and high pseudocapacitance of PPy. The foam electrodes with different layers of rGO/PPy from one to five were then obtained using alternate deposition method. The capacitance performances of all the electrodes were studied. The capacitance values of rGO/PPy-NF were greatly influenced by deposition voltage, deposition time, the concentration of GO, LiClO4, Py and TsOH. The layers of rGO/PPy also have a great effect on the electrochemical performance of rGO/PPy-NF. The rGO/PPy-NF-2L has the best capacitance performance among the foam electrodes with different layers of rGO/PPy, and its specific capacity is as high as 193.4 F/g at the current density of 1 A/g. The rGO/PPy-NF-2L also has good cycling stability. Its specific capacity remains 80% after 10000 times of the charge and discharge tests.