Facile synthesis of reduced graphene oxide-wrapped CNFs with controllable chemical reduction degree for enhanced microwave absorption performance.

The rGO-wrapped nanocomposites can be regarded as promising candidates for the development of advanced microwave absorbing materials. In this work, hierarchical rGO-wrapped CNFs were prepared via a two-step strategy, including a classical modified Hummers method and a green reduction reaction. Accompany with the chemical treatments, graphene oxide appears on the outer walls of carbon nanofibers. By modulating the addition amount of ascorbic acid, the outer graphene oxide can be controllably reduced. Moreover, the CNFs/rGO with proper reduction degree exhibits desirable microwave absorption performance, whose minimum RL and effective bandwidth are -38.1 dB (3.85 GHz, d = 5.0 mm) and 4.1 GHz (5.08-9.18 GHz, d = 3.5 mm). The superior microwave attenuation performance is attributed to the synergistic effects between the CNFs and rGO. While the nanofibers provide the obtained sample with an extremely long conductive network, rGO introduces a moderate amount of lattice defects and functional groups, resulting in desirable conductivity loss and multiple polarizations. The existence of rGO also endows CNFs/rGO with suitable dielectric values so that the absorber achieves well impedance matching. Considering the excellent microwave absorption performance, this research provides a new facile route to fabricate rGO-wrapped carbonaceous materials with proper oxygen-containing groups for MAMs.