▎ 摘　　要

The widespread application of high-frequency electronic and communication devices has caused increasingly severe electromagnetic pollution. It is highly desirable but challenging to develop ultralight electromagnetic wave (EMW) absorbers with strong absorption performance to eliminate the negative effects of electromagnetic pollution. Herein, a secondary ion adsorption and defect-anchoring strategy was proposed to construct ultralight N-doped graphene aerogels containing isolated single cobalt atoms (Co-SAs/GAs) with a tunable content of Co-SAs from 1.13 to 2.58 wt. %. The optimal Co-SAs/GAs with a matching thickness of 1.5 mm and an ultralow filler ratio of 5 wt. % attenuated about 99.999% electromagnetic energy and exhibited specific EMW absorption performance (SMAP) of 37 220 dB cm(2) g(-1), which was 15 000 dB cm(2) g(-1) higher than that of the best reported absorber in literature. Permittivity and electrical conductivity measurements indicated that the introduction of Co-SAs significantly increased the conduction and polarization losses of the GAs, which was confirmed by simulation results based on the Havriliak-Negami equation. Theoretical calculations demonstrated that the Co-N-4 moiety exhibited obvious polarization behavior, which could be further tuned by defective sites in its vicinity. This comprehensive investigation of the relationships between single-atom structure and electromagnetic wave absorption property provides an efficient route toward the rational design of ultralight absorbers with metal single-atoms.