Inner Surface-Functionalized Graphene Aerogel Microgranules with Static Microwave Attenuation and Dynamic Infrared Shielding.

Bulk graphene aerogels with high electrical conductivity, ultralow density, and high specific surface area have attracted significant attention because of their fascinating performances in energy storage, catalysis, absorption, sensor, electromagnetic shielding, etc. However, graphene aerogel microgranules (i.e., reducing the size of the bulk aerogels into microscale) and their performances in the electromagnetic field have been ignored. Herein, we report a new strategy to make floatable graphene aerogel microgranules with high hydrophobicity (137°), low density (13.5 mg/cm3), and high specific surface area (516 m2/g). These microgranules were synthesized initially from reduced graphene oxide (rGO) hydrogel microparticles and then in situ-modified by silica nanoparticles. Further investigations have demonstrated that the resulting silica-modified rGO aerogel microgranules possess highly efficient static electromagnetic screening (average 30.3 dB in 8-18 GHz) and dynamic infrared shielding (higher than 10 dB during floatation in air for 15 min) properties. The work reported here should give much inspiration to make more functional aerogel microgranules used in various emerging fields.