Rice husk derived hierarchical porous carbon with lightweight and efficient microwave absorption

Electromagnetic pollution is a threat to human health and electronic equipment. Therefore, studies on the means of absorbing electromagnetic waves are important. Wave absorbing material with the characteristic of lightweight and high microwave-absorption efficiency is in urgent demand. Biomass hierarchical porous carbon (BHPC) with micropores, mesopores, and macropores derived from rice husk was prepared using potassium hydroxide activation and one-step carbonization. The adjustment and optimization of the pore structure of BHPC can be realized by controlling the heat treatment temperature. When the thickness is 2.8 mm, the BHPC samples obtained at 650 °C show excellent electromagnetic wave absorption properties. The minimum reflection loss (RLmin) is - 47.463 dB at 9.796 GHz, and the effective absorption bandwidth accounts for 81% of the X-band (8.473–11.875 GHz). It shows good absorption performance for electromagnetic waves, due to good impedance matching, high dielectric-loss capacity, large specific surface area, and reasonable pore diameter distribution. This study suggests that the porous carbon from rice husk has a broad prospect as a lightweight and efficient electromagnetic absorbing material.