Macro-Micro Synergistic Design of C/TiO₂ Composites toward Efficient Electromagnetic Wave Absorbers

Biomass-derived carbon materials have attracted increasing attention due to their lightweight porous structures and tunable dielectric properties. However, their electromagnetic wave (EMW) absorption performance is still predominantly governed by the inheritance of natural pore channels, lacking cross-scale design from macroscopic geometry to microscopic interfaces. In this study, we propose a macro-micro synergistic regulation strategy and successfully synthesized balsa wood-derived porous carbon (BW) and its TiO₂ composites (BW/T) through facile high-temperature pyrolysis and hydrothermal methods. The hierarchical carbon framework provides multilevel scattering channels, while controlled graphitization ensures favorable impedance matching. Simultaneously, the incorporation of TiO₂ nanoparticles introduces abundant heterointerfaces and defect sites, which significantly enhance interfacial polarization and multiple relaxation processes. Benefiting from precise regulation of graphitic atomic configurations, the polarization loss is strengthened, enabling BW/T-1 to achieve an effective absorption bandwidth (EAB) covering the X-band with a minimum thickness of 2.97 mm. Furthermore, DFT and COMSOL simulations corroborate the crucial role of interfacial charge redistribution and enhanced polarization modes in energy dissipation. This work not only offers a new design concept for biomass-derived absorbers but also lays the foundation for extending cross-scale regulation strategies to electromagnetic protection and stealth applications.