Sodium ion induced synthesis of porous carbon for efficient electromagnetic wave absorption

Porous carbon is considered an excellent candidate material for electromagnetic wave absorption (EMWA) applications due to its distinctive microstructure. Herein, a series of porous carbon were synthesized by carbonizing sodium alginate powders at different temperatures (700 ℃, 800 ℃, and 900 ℃), followed by hydrochloric acid treatment. During the carbonization process, sodium ions in sodium alginate induce the formation of a porous structure by transforming into Na2CO3, which serves as a templating agent and an etching agent. The porous carbon prepared at 800 ℃ with a filler loading of 10 wt% exhibits a minimum reflection loss of -61.81 dB at a thickness of 5.10 mm and a maximum effective absorption bandwidth (EABmax) of 4.21 GHz at a thickness of 5.50 mm. In addition, the porous carbon prepared at 900 °C achieves a EABmax of 4.46 GHz at a thickness of 1.7 mm. Those outstanding EMWA performances mainly stem from the synergistic effects of interface polarization, dipole polarization, conductive loss, and microstructure. This work provides a straightforward and eco-friendly approach for the large-scale fabrication of porous carbon with excellent EMWA performance.