One-step pyrolysis derived Fe and heteroatom co-doped biochar composites for efficient microwave absorption

Electromagnetic (EM) pollution frequently disrupts the regular operation of sophisticated electrical devices, necessitating the urgent development of lightweight EM wave absorbers that possess powerful absorption capability. Herein, we report a simple method for the preparation of Fe and heteroatom co-doped biochar composites (FeX-BC, where X = N, S) by directly carbonizing the precursors of anhydrous FeCl₃, cherry kernel powder, and heteroatom dopants (melamine or Na₂S₂O₃·5H₂O). By adding different amounts of dopants during the synthesis of the precursors, it is possible to adjust the heteroatom content of the FeX-BC samples with precision. It is worth mentioning that the FeN_0.1-BC composite delivers the best EM wave absorption performance with an effective absorption bandwidth of 4.8 GHz and a minimal reflection loss of -63.2 dB. Furthermore, the significant attenuation of EM wave can be attributed to the synergistic interplay of magnetic loss, dielectric loss and the enhanced impedance matching. This study introduces a simple methodology for the fabrication of EM wave absorbers, a significant contribution to the synthesis, advancement, and functional applications of biomass-derived materials.