Microstructured CoFe-Doped rGO Aerogels for Highly Efficient Electromagnetic Wave Absorption

Constructing microstructures has become an effective way to enhance electromagnetic wave absorption (EMA) performance. In this study, cobalt (Co)–iron (Fe) alloy-doped reduced graphene oxide (rGO) aerogels (CoFe-rGO) with different microstructures were constructed using 1,2-epoxypropane as a catalyst and deionized water as the sole solvent, and their EMA properties, mechanisms, and sol–gel processes were investigated in detail. The results demonstrate that the microstructures of CoFe-rGO play a key role in their EMA properties and mechanisms. The representative CF-rGO-H2/Ar with a distinctive microstructure (namely folded rGO and square CoFe alloys) exhibits outstanding EMA performance in the low-, medium-, and high-frequency regions. In the medium- and high-frequency regions, the CF-rGO-H2/Ar exhibits an ultrabroad effective absorption bandwidth (EAB) of 8.08 GHz at an ultrathin matching thickness of only 1.65 mm and a minimum reflection loss of −45.69 dB at 2.47 mm. In the low-frequency region, CF-rGO-H2/Ar also possesses a maximum EAB of 2.64 GHz at a thickness of only 3.02 mm. CF-rGO-H2/Ar is also suitable for use in radar stealth technology. The excellent EMA properties are mainly attributed to its distinctive microstructure, which leads to high electrical conductivity of the folded rGO, multiple magnetic resonances of the square CoFe alloys, and superior impedance matching properties.