An efficientfficient, controllable and facile two-step synthesis strategy： Fe3O4@RGO composites with various Fe3O4 nanoparticles and their supercapacitance properties

An efficient, controllable, and facile two-step synthetic strategy to prepare graphene-based nanocomposites is proposed. A series of Fe3O4-decorated reduced graphene oxide （Fe3O4@RGO） nanocomposites incorporating Fe3O4 nanocrystals of various sizes were prepared by an ethanothermal method using graphene oxide （GO） and monodisperse Fe3O4 nanocrystals with diameters ranging from 4 to 10 nm. The morphologies and microstructures of the as-prepared composites were characterized by X-ray diffraction, Raman spectroscopy, nitrogen adsorption measurements, and transmission electron microscopy. The results show that GO can be reduced to graphene during the ethanothermal process, and that the Fe3O4 nanocrystals are well dispersed on the graphene sheets generated in the process. The analysis of the electrochemical properties of the Fe3O4@RGO materials shows that nanocomposites prepared with Fe3O4 nanocrystals of different sizes exhibit different electrochemical performances. Among all samples, FegO4@RGO prepared with Fe3O4 nanocrystals of 6 nm diameter possessed the highest specific capacitance of 481 F/g at 1 A/g, highlighting the excellent capability of this material. This work illustrates a promising route to develop graphene-based nanocomposite materials with a wide range of potential applications.

From Amorphous Carbon to Carbon Nanobelts and Vertically Oriented Graphene Nanosheets Synthesized by Plasma-enhanced Chemical Vapor Deposition

Carbon materials with various structures were produced via plasma-enhanced chemical vapor deposition by controlling substrate temperature and mixed gases in the atmosphere. Scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, high resolution transmission electron microscopy（HRTEM） and Raman spectroscopy were employed to investigate the morphology and structure of the materials. The results show that at a low substrate temperature（100 ~C） in CHa：Ar（flow rate ratio was 100 cm3/min：10 cm3/min）, amorphous carbon formed on Si（100） that could act as a support for the growth of carbon nanobelt and layer graphene at 800 ~C. Vertically oriented multi-layer graphene nanosheets（GNs） were catalyst-free synthesized on Si and Ni foam at 800 ~C in a mixture of CHa：Ar（20 cm3/min：60, 80 and 100 cm3/min）. The capacitor character investigated by cyclic voltammetry and galvanostatic charge/discharge indicates that for the as-synthesized GNs, the electrochemical capacitance is very small（16 F/g at current density of 16 A/g）. However, having been treated in acidic solution, the GNs exhibited good capacitive behavior, with a capacitance of 166 F/g, and after 800 charge/discharge cycles at 32 A/g, the capacitance could retain about 88.4%. The enhancement of specific capacitance is attributed to the increase of specific surface area after etching treatment of them.

Holey graphene hydrogel with in-plane pores for high- performance capacitive desalination

Capacitive deionization is an attractive approach to water desalination and treatment. To achieve efficient capacitative desalination, rationally designed electrodes with high specific capacitances, conductivities, and stabilities are necessary. Here we report the construction of a three-dimensional （3D） holey graphene hydrogel （HGH）. This material contains abundant in-plane pores, offering efficient ion transport pathways. Furthermore, it forms a highly interconnected network of graphene sheets, providing efficient electron transport pathways, and its 3D hierarchical porous structure can provide a large specific surface area for the adsorption and storage of ions. Consequently, HGH serves as a binder-free electrode material with excellent electrical conductivity. Cyclic voltammetry （CV） measurements indicate that the optimized HGH can achieve specific capacitances of 358.4 F.g 1 in 6 M KOH solution and 148 F.g-1 in 0.5 M NaCl solution. Because of these high capacitances, HGH has a desalination capadty as high as 26.8 mg.g-1 （applied potential： 1.2 V; initial NaCI concentration： -5,000 mg.L-l）.