Facile synthesis of N, S-codoped honeycomb-like C/NiS composites for broadband microwave absorption with low filler mass loading.

Manufacturing highly efficient microwave absorbents with powerful absorbing intensity, wide effective absorption bandwidth (RL < -10 dB, it means that 90% of the electromagnetic waves enter the absorber and are dissipated) and light weight at low filling loading is still a challenge. In this work, N, S-codoped honeycomb-like C/NiS composites were synthesized via a freeze-drying approach and following pyrolysis process under Ar atmosphere, using NaCl and sucrose as template and carbon source, respectively. When evaluated as a microwave absorbent, the as-obtained N, S-codoped honeycomb-like C/NiS composite pyrolyzed at 700 °C displayed high performance for microwave absorption including high absorption intensity (the maximum reflection loss of -46.8 dB at 13.4 GHz), broad effective absorbing bandwidth (7.0 GHz, 11.0-18.0 GHz) and relative low filling loading in paraffin (only 10 wt%). Such high performance of microwave absorption could be ascribed to the better impedance matching and stronger damping ability induced by unique honeycomb-like structure and suitable pyrolysis temperature. Importantly, our research might provide a facile and engineering strategy to explore other types of microwave absorbing materials to boost their microwave absorption at low filler loading.