Microwave absorption on a bare biomass derived holey silica-hybridized carbon absorbent

Developing lightweight and inexpensive absorbents with strong and broadband absorbing performance toward microwave radiation is a challenging but pressing task. Here we report that rice husk-derived silica-hybridized holey carbon fabricated by combining pyrolysis and plasma processing methods is active for the microwave absorbing. The obtained metal-free product is barely prepared from wasted biomass without any additive reagents addition. The results demonstrate at the thickness of 1.5 mm, its reflection loss reaches −43.0 dB at 13.36 GHz and the corresponding absorption bandwidth approaches 3.68 GHz (from 11.44 GHz to 15.12 GHz), over-performing most bare biomass-derived absorbents. The enhanced performance is attributed to the silica blocks existing on surface, which is inherited from the raw rice husk precursor and will construct abundant hybridized contact sites with the derived carbon matrix, thereby providing plenty of interfacial polarizations. Meanwhile, the post plasma treatment can generate rich tiny holes on the carbon matrix, and endow it with high surface areas associated with a great variety of defective sites, and hence regulating the dielectric loss of the final product. It is anticipated that these can represent a feasible addition to the family of wasted biomass-derived sustainable microwave absorbents.