Facile synthesis of nitrogen-doped cobalt/cobalt oxide/carbon/reduced graphene oxide nanocomposites for electromagnetic wave absorption

Electromagnetic wave absorption materials with strong absorption, thin thickness, broad bandwidth and low filler loading are highly desirable in the field of electromagnetic absorption. In this work, graphene oxide (GO) was firstly used as a template for growth of cobalt, zinc–zeolitic imidazolate frameworks (Co, Zn–ZIFs), and then nitrogen-doped cobalt/cobalt oxide/carbon/reduced graphene oxide (Co/CoO/C/RGO) nanocomposites were further constructed by the high-temperature pyrolysis strategy. Results of morphology observations demonstrated that numerous carbon frameworks with a slightly contracted polyhedron morphology were anchored on the crumpled surfaces of sheet-like RGO. Moreover, well-constructed structure of RGO loaded with carbon nanotubes wrapping carbon frameworks was observed, and considerable nitrogen atoms had been in situ doped into the porous carbon matrix of attained nanocomposites. Furthermore, the influences of filler loadings, calcination temperature, and addition of GO on the electromagnetic parameters and absorption performance of obtained nanocomposites were investigated. Results revealed that the addition of GO notably strengthened the electromagnetic absorption performance. Remarkably, the percolation transition was observed in the filler loading range of 20–25 wt%. The as-synthesized nanocomposite under 700 °C calcination treatment exhibited superior electromagnetic absorption performance with an optimal reflection loss of −63.0 dB and effective absorption bandwidth of 4.0 GHz (12.2–16.2 GHz) at a thin matching thickness of merely 1.6 mm and filler loading as low as 25 wt%. In addition, the underlying electromagnetic absorption mechanisms were proposed. This work provided a facile strategy for fabricating the carbon-based magnetic composites derived from metal–organic frameworks as light weight and high-performance electromagnetic absorption materials.