Synthesis Of Graphene-based Composite Materials For Eergy Materials

Graphene, with large surface area, good mechanical strength and good electrical conductivity, has been applicated and developed in the field of energy storage/conversion and biomedicine, also provides a new opportunity for the development of graphene-based composite materials. And porous materials built up by graphene-based composite materials have much more excellent properties. Graphene can enhance the stability of the porous frameworks and conductivity of materials; porous frameworks can promote the infiltration of electrolyte and shorten the transmission path of electrons. Nevertheless, the controllability of metal oxide's growth and pore size is poor, which can't play the advantages of them well.In this study, we apply two strategies:(1) Employing polymer and carbon-coating as coupling linker to strengthen the cohesiveness of metal oxide nanoparticles and graphene, also to protect metal oxide nanoparticles and adjust its uniform distribution; (2) Porous materials built up by composite materials with controllable sizes of porous and oxide nanoparticles. In our study, we design different strategies for the applications of materials. Furthermore, the materials were characterized and tested later. The contents are listed as follows:(1) The Synthesis of 3D carbon encapsulated Fe3O4/graphene framework with oriented macropores. We report a facile fabrication of C-Fe3O4/G by the ice-segregation-induced self-assembly (ISISA) of graphene oxide nanosheets loaded with FeOOH NPs (FeOOH/GO) and polyvinyl alcohol (PVA) and the following thermal treatment. During the thermal treatment step, PVA wrapping around FeOOH/GO can be converted to a carbon shell. The highly oriented 3D macroporous framework can not only promote the infiltration of electrolyte and shortening Li ion diffusion length, but also reduce the electrode polarization at high charging/discharging rate; the carbon shells can be effectively reduce the transport resistance of lithium ions and prevent the pulverization of Fe3O4 NPs. As the anode material in LIBs, C-Fe3O4/G with Fe3O4 content of 60 wt%exhibits an increasing capacity with the charge/discharge cycles and delivers a high capacity of 1065 mA h g-1 at a current density of 0.2 A g-1 after 200 cycles. Even at a high current density of 8 A g-1, the electrode still achieved a high capacity of 470 mA h g-1.(2) The Synthesis of 2D mesoporous nitrogen-doped carbon/graphene nanosheets. We present a general and efficient strategy towards M-NCG with a unique two-dimensional (2D) morphology and mesoscale porosity. In our approach, SnO2 are grown on a graphene surface with in situ polymerization of aniline, followed by thermal treatment in nitrogen atmosphere and etching by acid. The existence of a large number of mesopores and micropores in the samples are verified by characterization of materials. The resulting samples possess large amount of micro/mesoporous, which is provide more active sites for reaction. As the cathode catalyst of fuel cell, it showed excellent performance of ORR.