Trimodal pore engineering on biomass-derived carbon composites for efficient microwave absorption

To achieve enhanced microwave absorption (MA) performance, the elaborate control of material microstructures has become an attractive research direction. However, the specific correlation between multiscale structures and electromagnetic (EM) properties remains unclear, hindering the advancement of better performance absorbers. Using soybean as the precursor, hierarchical biomass-derived porous carbon (HBPC) with rationally constructed trimodal micro-meso-macro pores was successfully fabricated by a combination of blowing-assisted pyrolysis and chemical etching processes. The trimodal pore structures influence dielectric properties by enhancing interfacial polarization and electrical conductivity. And novel regulatory mechanisms of the interfacial polarization process were revealed based on the conduction-polarization coupling effect, providing an important rationale for the collaborative design of multi-scale pore structures. Mesopores and micropores provide abundant active sites to induce interfacial polarization, while interconnected macropores enhance the connectivity of the electrically conducting network within the composite. The novel trimodal design effectively combines the large specific surface area of nanopores with the transport advantages of macropores, presenting an important synergistic effect in enhancing microwave attenuation capacity compared to counterparts with only micropores, mesopores or bimodal micro/mesopores. These findings reveal an intrinsic dependence of dielectric functionality on porous structures at different scales, providing crucial guidance for the design and engineering of hierarchical architectures. Excellent MA performance is achieved with a superior reflection loss of −62.8 dB and a broad absorption bandwidth of 4.24 GHz. Overall, the trimodal pore engineering strategy implemented in this work opens up new possibilities for the development of high-performance microwave absorbers.