Combining hollow materials with magnetic particles to construct hierarchical structures favors enhancement of microwave absorption properties. However, the fabrication of the well-defined materials possessing both hollow and hierarchical features still faces a huge challenge. Herein, a facile two-step method is developed to synthesize hierarchically nitrogen-doped carbon hollow microspheres assembled with loose and porous magnetic carbon sheets. Especially, many magnetic Fe/Fe₃C NPs covered with N-doped graphitic layers are embedded in the mesoporous N-doped carbon sheets layers. Benefited from the special structure, the optimal nitrogen-doped carbon hollow microspheres exhibit an excellent microwave absorption property with an EAB of ∼4.00 GHz at a thickness of 2.5 mm and the minimal reflection loss of −39.87 dB at a frequency of 7.76 GHz, while the filler ratio is only 10 wt% in the paraffin wax. Electromagnetic parameters analysis reveals that unique hierarchical structure and rich heterogeneous interfaces result in the enhancement of dielectric and magnetic losses as well as optimized the impedance matching. The computer simulation technology (CST) simulation further verifies the practical applicability of the optimal nitrogen-doped carbon hollow microspheres. This work provides an effective way for the efficient synthesis of hierarchical and hollow materials for microwave absorption.

将中空材料与磁性颗粒结合构建分层结构有利于增强微波吸收性能。然而，同时具有中空和分层特征的定义明确的材料的制造仍然面临着巨大的挑战。在此，开发了一种简便的两步法来合成由松散多孔磁性碳片组装的分层氮掺杂碳空心微球。特别是，许多覆盖有N掺杂石墨层的磁性 Fe/Fe ₃ C NPs嵌入中孔N-掺杂的碳片层。得益于特殊的结构，最佳的氮掺杂碳空心微球表现出优异的微波吸收性能，厚度为 2.5 mm 时的 EAB 为 ~4.00 GHz，频率为 7.76 GHz 时的最小反射损耗为 -39.87 dB，而石蜡中的填料比例仅为10 wt%。电磁参数分析表明，独特的层次结构和丰富的异质界面导致介电和磁损耗的增强以及阻抗匹配的优化。计算机模拟技术（CST）模拟进一步验证了优化的氮掺杂碳空心微球的实际适用性。该工作为高效合成多级中空微波吸收材料提供了一种有效途径。