Hierarchical porous structures with heterogeneous interfaces in CoC@(C/rGO) nanocomposites for broadband electromagnetic wave absorption

Abstract

The integration of biomass-derived porous carbon with magnetic components offers an effective strategy for developing high-efficiency broadband electromagnetic wave (EMW) absorbers. In this work, a hierarchical porous CoC@(C/rGO) composite was synthesized via freeze-drying and pyrolysis, using a hybrid carbon precursor composed of one-dimensional cellulose nanofibers (CNFs) and two-dimensional graphene oxide (GO), together with zero-dimensional ZIF-67 as the magnetic source. The absorber consists of cobalt-carbon particles (CoC) coated with cellulose-derived carbon and reduced graphene oxide (C/rGO), forming a hierarchical porous structure with abundant heterogeneous interfaces. The CoC@(C/rGO)-III composite exhibits a minimum reflection loss (RL_min) of −51.95 dB at a thickness of 2.3 mm and an effective absorption bandwidth (EAB) of 7.74 GHz. The hierarchical porous framework, constructed from the pyrolyzed carbon layer of CNFs and GO nanosheets, promotes multiple reflections and scattering of EMWs. Heterogeneous interfaces and defect sites enhance dipole and interfacial polarization, while the incorporated Co nanoparticles contribute to magnetic loss. Density functional theory (DFT) calculations reveal that the heterostructure facilitates charge carrier migration, promoting electron transfer at interfaces and thereby strengthening interfacial polarization. This study presents a pragmatic strategy for designing highly efficient carbon-based EMW absorbers through multi-scale structural regulation.