Abstract: The low surface energy and hierarchical micro/nanostructures endow microwave-absorbing materials with superhydrophobicity to avoid the adverse effects of high-humidity environments on their performance and structure. Notably, fluoridizing engineering can meet these requirements by regulating the material morphology, defect distribution, surface polarization and forming hydrophobic structures. In this study, we designed a combined oxidation-fluoridizing method to obtain an electromagnetic wave absorbing and superhydrophobic material, namely, fluoridizing graphene@copper (F-GE@Cu) hybrids with multi-interfacial heterostructures. This strategy involved the oxidation of graphene-wrapped Cu nanoparticles (GE@Cu) prepared by the thermal decomposition of cupric tartrate to GE@Cu_xO (x = 1 and 2) and further fluorination by PTFE pyrolysis to obtain F-GE@Cu with a yolk-shell structure. Multi-interfacial heterostructures were achieved using precise modulation of the Cu particle, carbon-cladding layer, and fluoridizing products such as CuF₂ and fluorinated graphene (FGE), this resulted in improved interfacial polarization and impedance matching to achieve satisfactory broadband and electromagnetic wave loss performance. Consequently, the as-prepared fluorinated graphene@copper fluoride (FGE@CuF₂) exhibited high performance for electromagnetic wave (EMW) absorption with an intense reflection loss (RL_min) of -53.0 dB and a broad effective bandwidth (EAB) of 8.9 GHz (9.1-18.0 GHz). Additionally, the FGE cladding conferred the hybrids with excellent superhydrophobic properties (WAC=154.0°), allowing it to tolerate diverse and harsh water-containing environments, providing the microwave-absorbing coatings with a universal waterproofing capability. This study presents a new strategy for preparing multifunctional electromagnetic wave-absorbing materials.

Key words: Fluoridation, Multi-interfacial heterostructure, Yolk-shell structure, Microwave absorption, Superhydrophobicity