Hierarchically porous biochar derived from orthometric integration of wooden and bacterial celluloses for high-performance electromagnetic wave absorption

Abstract

Inspired by the natural growth of wooden cellulose (WC) and bacterial cellulose (BC), we integrated the two categories of cellulosic materials by static fermentation. BC networks created in plane are intimately integrated with the wooden chip (cross section of wood, CW) and are perpendicular to the orientation of the cellular channels along the growth of the trees. The as-prepared BC/CW composites were converted into the interconnected carbon monoliths with hierarchically porous structure (CBC/CCW) by a one-step carbonization. The complementarity of WC and BC in spatial orientation created more mixed meso/macropores. Upon EMW irradiation, the wood-derived carbonaceous cellular wall attenuates EM energy by multiple reflection, while CBC networks further dissipate EMW by conduction loss. Additionally, the abundant voids inside of the wooden channels are beneficial to impedance matching. As a result, the as-fabricated three-dimensional CBC/CCW composites infiltrated with polydimethylsiloxane delivered strong EMW absorption performance with minimum reflection loss of −57.97 dB, broad absorption bandwidth of 6.28 GHz, and ultralow filler loading of 3.5%. Moreover, the elastomer CBC/CCW can still maintain 90% EMW absorption capability even after 500 bending-releasing cycles. The ingenious integration of wooden and bacterial celluloses provides a new sight for designing high-performance EMW absorbers with low-cost and sustainable resources.