In this work, the bamboo charcoal with a natural gradient structure is prepared via a one-step pyrolysis process, exhibiting excellent electromagnetic interference (EMI) shielding performance. The relationship between preparation conditions, microstructure, and EMI shielding properties was systematically investigated and discussed in detail.

Biochar materials have become an emerging choice for electromagnetic interference (EMI) shielding functional materials due to their inherent layered porous structure and sustainability. However, previous studies have primarily focused on the compositional and structural design of biochar with functional nanomaterials and overlooked the relationship between its intrinsic physicochemical properties and EMI shielding performance. In this study, the relationship between the preparation conditions of bamboo charcoal (BC) and its subsequent microstructure evolution, phase composition, electrical conductivity, and EMI shielding properties is investigated. BC with abundant hierarchical pores and continuous conductive networks is prepared by a one-step pyrolysis process. This structure facilitates the internal conduction of electrons, thereby enhancing EMI shielding performance. Notably, the electrical conductivity of BC is sharply improved from 1.3 × 10⁻⁵ to 31.2 S cm⁻¹ as the pyrolysis temperature increases from 600 to 1000 °C. Correspondingly, the EMI shielding effectiveness (EMI SE) improves from 0.29 to 73.63 dB with a shielding efficiency exceeding 99.99%, demonstrating exceptional EM wave shielding capabilities. The continuous conductive networks induced by increased carbonization degree cause a pronounced impedance mismatch between the air and the BC surface, leading to intense EM wave reflections. This work unlocks a novel prospect for the high-value utilization of bamboo resources.