Enhancing Interfacial Polarization through Electron Accumulation in Carbon Nanotube-Encapsulated α-Fe₂O₃ for Highly Efficient Microwave Absorption

Interface polarization (one of the slow polarizations) is considered the primary mechanism driving microwave absorption (MA), but limitations in material composition and microstructure design often lead to weak interfacial polarization relaxation. In this work, we developed an interesting heterostructure consisting of carbon nanotube-encapsulated α-Fe₂O₃ nanocolumns (CNTs@α-Fe₂O₃). The curvature effects of CNTs induce a built-in electric field between CNTs and α-Fe₂O₃ nanocolumns, facilitating effective interface polarization. Under microwave irradiation, electron accumulation at the interfaces, driven by the energy-level mismatch between the two materials, further strengthens interface polarization, leading to a highly efficient MA performance. This heterostructured material achieves a minimum reflection loss of -74.1 dB at a thickness of 1.8 mm and an effective absorption bandwidth (reflection loss ≤ -10 dB) of 5.2 GHz (11.9 ∼ 17.1 GHz) at a thickness of only 1.5 mm. X-ray photoelectron spectroscopy and Raman scattering show a distinct blueshift in the Fe 2p binding energy and the A_1g mode energy (exclusively associated with Fe atom vibrations), suggesting substantial charge transfer and redistribution at the interface associated with enhanced interface polarization. This work provides insights into interface polarization through the strategic design of energy levels and materials.