Hierarchically porous carbon derived from natural Porphyra for excellent electromagnetic wave absorption

• The porphyra-derived porous carbon (PPC) was fabricated via facile procedures of low temperature pre-carbonization combined with KOH chemical activation. • The porosity of PPC can be readily regulated by adjusting activation temperature. • The hierarchically porous carbon exhibits excellent electromagnetic wave absorption performances. A highly efficient absorber with features including lightweight, broad bandwidth, and tunable electromagnetic property still remains challenging for practical applications. Herein, the Porphyra - derived porous carbon (PPC) was fabricated via facile procedures of low-temperature pre-carbonization combined with KOH chemical activation. The composition, microstructure, and electromagnetic wave absorption properties of the samples were elucidated based on X-ray diffraction (XRD), Raman, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer−Emmer−Teller (BET), and vector network analyzer (VNA). The porosity of PPC can be readily regulated by adjusting activation temperature. The PPC obtained at 750 °C was composed of a three-dimensional hierarchically porous carbon network. The C and N elements of natural Porphyra were introduced into the carbon skeleton during the carbonization process. The large specific surface, dopants, and three-dimensional hierarchically porous carbon network can effectively improve the impedance matching and dielectric dissipation, leading to an excellent electromagnetic wave absorption performance. Especially, the optimal reflection loss (RL) value reached –57.75 dB at 9.68 GHz with a broad bandwidth (RL < –10 dB) value of 7.60 GHz at 3.5 mm. Overall, the results indicate that the PPC can provide a new way to achieve lightweight, effective, and sustainable absorbers.