Dopamine-assisted one-pot synthesis of graphene@Ni@C composites and their enhanced microwave absorption performance

• Graphene@Ni@C has been synthesized via a dopamine-assisted one-pot synthesis.
• The sandwich-structured composites have a ferromagnetic behavior.
• The diameter of Ni particles is in the range of 20–50 nm.
• The maximum reflection loss of the composites is −34.2 dB at 13.9 GHz.
• The absorption bandwidths exceeding −10 dB are 3.2 GHz with a thickness of 1.6 mm.

A novel sandwich-structured composites of graphene@Ni@C have been successfully synthesized via a facile one-pot method by using dopamine as reducing agent and carbon source. TEM and SEM images reveal that the average diameter of Ni particles ranges from 20 to 50 nm and these Ni particles anchored on grephene sheets are completely covered by N-doped carbon coatings. The investigation of the microwave absorbability reveals that the composites exhibit enhanced microwave absorption properties in terms of both the maximum reflection loss and the absorption bandwidths compared with graphene@C. The maximum reflection loss of graphene@Ni@C is −34.2 dB at 13.9 GHz and the absorption bandwidths below −10 dB is 3.2 GHz with a thickness of only 1.6 mm, which makes the composites can be used as lightweight microwave absorption materials. Furthermore, our strategy paves a facile method to design the sandwich-structured nanostructures in microwave absorbing area.