Nanocellulose-assisted construction of multi-cavity structured Ti₃C₂T_x/melamine composite sponges for enhanced electromagnetic interference shielding

The deposition of Ti₃C₂T_x nanosheets onto an ultralight melamine sponge (MS) holds great appeal for constructing mechanically robust and high-performance electromagnetic interference (EMI) shielding composites. However, the full potential of Ti₃C₂T_x materials for shielding performance is impeded by the insufficient affinity between Ti₃C₂T_x nanosheets and MS. Herein, with the assistance of cellulose nanofibers (CNF), large-sized single-layer Ti₃C₂T_x nanosheets were firmly attached to the MS skeleton and enveloped the pores. The obtained Ti₃C₂T_x/MS composite sponges exhibit a unique multi-cavity structure. Moreover, hydrophobic modification was applied to the composites through the use of two-component silane coupling agents. The silane-modified multi-cavity structured composite sponges demonstrate significant enhancements in conductivity, mechanical strength, and environmental stability. Particularly, the incorporation of 17 wt% CNF leads to a 29.3 dB increases in shielding efficiency (SE) for the composite sponge. The enhancement can be attributed to the high reflectance of electromagnetic waves due to the highly conductive Ti₃C₂T_x/CNF cavity-membranes, the multiple internal reflections within the multi-cavity structure, and the improved interfacial polarization loss capability facilitated by the abundance of MXene-CNF interfaces.