Constructing graphene-based aerogel with bi-continuous interpenetrating networks as a multi-functional microwave absorber

The design of three-dimensional networks in graphene-based aerogels is an effective strategy for fabricating a lightweight microwave absorber with strong absorption and broad effective bandwidth. Herein, a multi -functional aerogel with bi-continuous interpenetrating networks comprised of reduced graphene oxide (RGO) and cellulose nanofiber (CNF) was developed via an "ice -dissolving" (freezing and solvent exchange) and subsequent annealing strategy. Different from the conventional step-by-step construction of two independent networks, the bi-continuous interpenetrating networks were simultaneously built in a one-step freezing process. Notably, the network structure of the aerogel can be tuned by adjusting the concentration of CNF (CCNF) during the freezing stage. When the CCNF increased from 2 to 8 wt%, the network structure transitioned from a single three-dimensional RGO skeleton to ordered bi-continuous interpenetrating networks, and then to a disordered CNF/RGO mixed network. The mutual contributions from the RGO skeleton and CNF network endowed the aerogel (14.96 mg cm -3) with improved conduct loss and optimized characteristic impedance, leading to an excellent microwave absorption capacity. Consequently, the aerogel achieved a maximum reflection loss of -68.3 dB and an effective bandwidth of 6.9 GHz, respectively. Moreover, the unique network structure also enabled the sample to have superior noise absorbing performance (normalized absorption coefficient of 0.894 in 250-6300 Hz) and good structural stability. This strategy provides a facile avenue for constructing multifunctional aerogels with bi-continuous interpenetrating networks for both microwave absorption and noise absorption applications.