Biomass-derived ultralight superior microwave absorber Towards X and Ku bands.

Biomass-derived microwave absorbers have attracted extensive attention due to their natural abundance, low cost and eco-friendliness. However, it is still a challenge to achieve superior absorptivity under the extremely low filler content in such absorbers. Herein, we engineer a hybrid of CoFe alloy nanoparticles (NPs) anchoring on the biomass shaddock peel derived porous carbon nanosheets (CNs) for superlight and efficient microwave absorption. The CNs exhibit attractive graphene-like morphology with CoFe alloy NPs uniformly dispersing throughout the CNs. It is revealed that the EM parameters could be well controlled by tailoring the deposition ratio of CoFe NPs to optimize impedance matching. Specifically, the sample with relatively sparse CoFe NPs exhibit a reflection loss (RL) of -22.3 dB and broad absorption bandwidth of 5.3 GHz in Ku band under the ultralow filler content of only 8.0 wt%. As the deposition ratio of magnetic CoFe NPs increases, the optimized absorption peak moves to X band with -50.6 dB of RL value and 4.5 GHz of effective absorption, completely covering the whole X band. The elaborative studies demonstrate the significant influence of impedance matching on the ultimate absorption performance. This work paves a new way for the development of biomass-derived composites as superlight and tunable microwave absorber.