Hierarchical Intercalation−Passivation Engineering Enables Environmentally Durable MXene Nanosheet Janus Films for EMI Shielding and Thermal Management

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The restacking and environmental oxidation of Ti3C2Tx MXene remain major obstacles to maintaining the electrical and functional stability of MXene-based electromagnetic interference (EMI) shielding films. Here, a hierarchical protection architecture was constructed in a Janus composite film by combining internal interfacial stabilization with external surface passivation. Gallic-acid-modified single-walled carbon nanotubes (GA/SWCNT) were intercalated between MXene nanosheets to alleviate restacking, establish interconnected conductive pathways, and retard oxidation of the MXene network. The conductive layer was supported by aramid nanofibers, followed by deposition of an approximately 200 nm Al layer that spontaneously formed a surface Al2O3 passivation layer, providing an additional protective surface layer. The resulting Al/GA-SWCNT-MXene/ANF (AGCM) Janus film exhibited an average EMI shielding effectiveness of 48.28 dB in the X-band and a thickness-normalized specific shielding effectiveness (SSE/t) of 20221.6 dB·cm2·g−1. After thermal aging, UV irradiation, salt-spray exposure, and 50 day outdoor aging, the maximum decrease in EMI shielding effectiveness was 2.2%. The film also reached 178.1 °C at 4.0 V and maintained a stable electrothermal response during ten heating cycles and 15,000 s of continuous operation. At an actual surface temperature of 130 °C, its apparent infrared temperature was 49.2 °C, 32.6 °C lower than that of the uncoated GCM film. These results demonstrate that hierarchical interfacial and surface stabilization provides a viable route to combine environmental durability with EMI shielding, electrothermal conversion, and infrared signature suppression in MXene-based films.