Hollow N-doped carbon polyhedrons embedded Co and Mo₂C nanoparticles for high-efficiency and wideband microwave absorption

Carbon materials with multi-components and hollow structures can be used as promising candidates in microwave absorption materials, however, rational design and construction of the special structures is still hard to achieve. In this work, a hollow structural bimetallic carbon polyhedron (CoMo@HNCP) is synthesized by the pyrolysis of core-shell ZIF-8@HZIF-CoMo polyhedrons. Owing to the uniform distribution of Mo₂C and metallic Co nanoparticles in the hollow N-doped carbon shell, the generated multi-heterogeneous interfaces are in favor of dipolar and interfacial polarization, resulting in enhanced conduction loss, matched impedance as well as multiple scatterings. Typically, with a filler loading of 30 wt%, the minimum R_L of CoMo@HNCP reaches −44.8 dB and the effective absorption bandwidth is as wide as 6.56 GHz with the absorber thickness of 2.5 mm, which is better than that of ZIF-8 derived N-doped carbon polyhedron and HZIF-CoMo derived bimetallic carbon polyhedron. The usage of bimetallic HZIF to assemble core-shell nanomaterials is proven to be an novel and excellent way to assembly microwave absorbers with multi-heterogeneous interfaces and hollow structures.