Two-dimensional transition-metal carbides/carbonitrides (MXenes) with both superb electrical conductivity and hydrophilicity are promising for fabricating multifunctional nanomaterials and nanocomposites. However, the construction of three-dimensional (3D) and lightweight MXene macroscopic assemblies with excellent electrical conductivity and mechanical performances has not been realized due to the weak gelation capability of MXene sheets. Herein, we demonstrate an efficient approach for constructing highly conductive 3D Ti₃C₂T_x porous architectures by graphene oxide assisted hydrothermal assembly followed by directional freezing and freeze-drying. The resultant hybrid aerogels exhibit aligned cellular microstructure, in which the graphene sheets serve as the inner skeleton, while the compactly attached Ti₃C₂T_x sheets present as shells of the cell walls. The porous and highly conductive architecture (up to 1085 S m^–1) is highly efficient in endowing epoxy nanocomposite with a high electrical conductivity of 695.9 S m^–1 and an outstanding electromagnetic interference (EMI)-shielding effectiveness of more than 50 dB in the X-band at a low Ti₃C₂T_x content of 0.74 vol %, which are the best results for polymer nanocomposites with similar loadings of MXene so far. The successful assembly methodology of 3D and porous architectures of Ti₃C₂T_x would greatly widen the practical applications of MXenes in the fields of EMI shielding, supercapacitors, and sensors.

中文翻译：

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具有出色电磁干扰屏蔽性能的高导电性三维Ti ₃ C ₂ T _x MXene /还原氧化石墨烯混合气凝胶

具有优异的导电性和亲水性的二维过渡金属碳化物/碳氮化物（MXenes）有望用于制造多功能纳米材料和纳米复合材料。但是，由于MXene片材的胶凝能力较弱，因此尚未实现具有优异的导电性和机械性能的三维（3D）轻质MXene宏观组件的构造。在这里，我们演示了一种构造高导电性3D Ti ₃ C ₂ T _x的有效方法氧化石墨烯辅助的水热组装，然后进行定向冷冻和冷冻干燥，从而形成多孔结构。所得的混合气凝胶表现出对齐的细胞微观结构，其中石墨烯片充当内部骨架，而紧密附着的Ti ₃ C ₂ T _x片则作为细胞壁的壳而存在。多孔且高导电性的体系结构（高达1085 S m ^–1）在赋予环氧纳米复合材料方面非常有效，具有695.9 S m ^–1的高电导率和出色的电磁干扰（EMI）屏蔽效果，超过50 dB。 Ti ₃ C ₂ T _x低时的X波段含量为0.74％（体积），这是迄今为止具有相似MXene含量的聚合物纳米复合材料的最佳结果。Ti ₃ C ₂ T _x的3D和多孔结构的成功组装方法将极大地扩展MXene在EMI屏蔽，超级电容器和传感器领域的实际应用。