Hierarchically porous carbons with controlled structures for efficient microwave absorption

To probe the influence of the porous morphology of carbon materials on their microwave absorption performance, hierarchically porous carbons (HPCs) with designed structures have been successfully prepared starting from poly(divinylbenzene) by emulsion template polymerization. There exist two levels of pores in the obtained HPCs. One level of micro-scale pores templates from the water drops, and the other level of nano-scale pores is created during KOH activation in the subsequent carbonization process. By adjusting the water volume fraction during polymerization and the KOH dosage, both micro- and nano-scale porous structures can be accurately tuned. The influences of pores with diverse scales on microwave adsorption capacity are investigated in detail. Eventually, the maximum reflection loss of −56.4 dB and an effective adsorption bandwidth of 6.0 GHz are achieved. The superior microwave absorption performance of HPCs is attributed to the superimposed contributions of the two-level pores to the enhancement of polarization abilities and the multiple reflections of the microwave.