2D/1D Hierarchical Hollow NiO@PPy Composites with Tunable Dielectric Properties for Enhanced Electromagnetic Wave Absorption

The development of diverse microstructures has substantially contributed to recent progress in high-performance electromagnetic wave (EMW) absorption materials, providing a versatile platform for the modulation of absorption properties. Exploring multidimensional microstructures and developing tailored and gentle strategies for their precise optimization can substantially address the current challenges posed by relatively unclear underlying mechanisms. Here, a series of 2D/1D heterogeneous NiO@PPy composites featuring hollow hierarchical microstructures are successfully synthesized using a straightforward strategy combining sacrificial templating with chemical oxidative polymerization. This strategy offers a facile and effective approach to fine-tune the microstructure by adjusting the thickness of the polypyrrole (PPy) coating. This enables the continuous optimization of the dielectric properties and specific microstructures to maximize EMW absorption. Remarkably, the optimized 2D/1D hierarchical hollow NiO@PPy composite demonstrates an ultrathin thickness of 2.3 mm, a wide effective absorption band spanning 5.89 GHz, and a strong absorption intensity of -71.65 dB at a minimal loading of only 10 wt.%. The proposed mild and controllable preparation strategy not only provides insights for further tailoring the optimal dielectric properties of specific structures to enhance the absorption capacity, but also enriches the exploration of the underlying absorption mechanisms from the perspective of microstructure regulation.