Guoxian Li

Laminated magnetic graphene with enhanced electromagnetic wave absorption properties

Graphene is highly desirable as an electromagnetic wave absorber because of its high dielectric loss and low density. Nevertheless, pure graphene is found to be non-magnetic and contributes to microwave energy absorption mostly because of its dielectric loss, and the electromagnetic parameters of pure graphene, which are out of balance, result in a bad impedance matching characteristic. In this paper, we report a facile solvothermal route to synthesize laminated magnetic graphene. The results show that there have been significant changes in the electromagnetic properties of magnetic graphene when compared with pure graphene. Especially the dielectric Cole–Cole semicircle suggests that there are Debye relaxation processes in the laminated magnetic graphene, which prove beneficial to enhance the dielectric loss. We also proposed an electromagnetic complementary theory to explain how laminated magnetic graphene, with the combined advantages of graphene and magnetic particles, helps to improve the standard of impedance matching for electromagnetic wave absorbing materials. Besides, microwave absorption properties indicate that the reflection loss of the as-prepared composite is below −10 dB (90% absorption) at 10.4–13.2 GHz with a coating layer thickness of 2.0 mm. This further confirms that the nanoscale surface modification of magnetic particles on graphene makes graphene-based composites have a certain research value in electromagnetic wave absorption.

Structural and electrochemical characterization of ordered mesoporous carbon-reduced graphene oxide nanocomposites

Ordered mesoporous carbon-reduced graphene oxide (OMC-RGO) composites were prepared using a solvent evaporation induced self-assembly method. We proposed a novel theory called Hanger–Bridge theory to explain how mesoporous carbon prevents RGO from agglomerating, and the RGO enhances the conductivity of mesoporous carbon as well as helping to load more Pt particles. The as-prepared OMC-RGO composites were used as catalyst supports to deposit Pt nanoparticles and facilitate electrocatalytic reactions as well. Furthermore, we discussed the structure and electrochemical performance differences between OMC supported Pt (OMC/Pt) and OMC-RGO supported Pt (OMC-RGO/Pt). Cyclic voltammetry measurements suggest that OMC-RGO/Pt shows an excellent electrochemical active area (6.81 times as big as OMC/Pt), enhanced catalytic activity towards methanol oxidation (6.67 times the highest current density than OMC/Pt), which could be attributed to the unique nanostructure of the catalyst: a high mesoporous structure and the conductivity of the composites, and highly distributed Pt nanoparticles.