Bamboo-Inspired Hierarchically Hollow Aerogel MXene Fibers with Ultrafast Ionic Channels and Multiple Electromagnetic Wave Attenuation Routes Toward High-Performance Supercapacitors and Microwave Absorption

2D materials feature large specific surface areas and abundant active sites, showing great potential in energy storage and conversion. However, the dense, stacked structure severely restricts its practical application. Inspired by the structure of bamboo in nature, hollow interior and porous exterior wall, hollow MXene aerogel fiber (HA-Ti₃C₂T_X fiber) is proposed. Owing to continuous porous microstructure and optimized hollow cavity, this fiber possesses large accessible area to ions and abundant structural defects, leading to a fast charge transfer kinetics and high faradic activity. Consequently, the HA-Ti₃C₂T_X fiber exhibits exceptional gravimetric capacitance of 355 F g⁻¹. Besides, the solid-state asymmetric fiber-shaped supercapacitors (FSCs) display a high capacitance of 276 F g⁻¹ and energy density of 9.58 Wh kg⁻¹. Additionally, the HA-Ti₃C₂T_X fiber delivers outstanding electromagnetic wave (EMW) absorption performance with a minimum reflection loss of −52.39 dB and the effective absorption bandwidth up to 4.6 GHz, which is attributed to multiple reflection paths, strong dielectric loss from this hollow and porous structure. This novel design of hollow fiber provides a new reference for the construction of advanced fibers for energy storage and EMW absorption materials.