We reported a facile one-pot polyol route for the fabrication of CoNi/nitrogen-doped graphene hybrids as synergistic microwave absorber. Microstructure investigations suggest that all the CoNi nanocrystals are uniformly anchored on the nitrogen-doped graphene nanosheets without aggregation and the hybrids are stable under ultrasound treatment, which suggest that these nonvalent CoNi alloys are in-situ grown on nitrogen-doped graphene with a strong interaction. Taking both the synergistic benefits of magnetic CoNi nanocrystals and electric nitrogen-doped graphene, the CoNi/nitrogen-doped graphene hybrids show a maximum reflection loss of −22 dB at 10 GHz with a matching thickness of only 2.0 mm, and the effective absorption bandwidth with reflection loss exceeding −10 dB is 3.6–18 GHz with the absorber thickness of 1.35–5.0 mm. Compared with the single CoNi nanocrystals and graphene oxide, the CoNi/nitrogen-doped graphene hybrids show improved microwave absorption properties. These results indicate that the interface interactions and synergistic effect between the CoNi nanocrystals and nitrogen-doped graphene play a significant role on the enhancement of microwave absorption properties. This work suggests that the CoNi/nitrogen-doped graphene hybrids can be used as candidate materials for the design and manufacture of electronic nanodevices with high efficient microwave absorption properties.

Interfacial interactions and synergistic effect of CoNi nanocrystals and nitrogen-doped graphene in a composite microwave absorber