Abstract: Heterointerface engineering based on built-in electric field (BIEF) has been well-received in electromag-netic wave (EMW) absorption. However, the influence of interface size and number of interfaces on the BIEF and interface polarization loss mechanism remains unclear. Here, we designed a ternary dual het-erointerfaces Co@C/SiO₂ nanocomposite. Experimental and theoretical analyses show that Co@C/SiO₂ has abundant Mott-Schottky heterointerfaces, and a reasonable increase in the heterointerface area leads to a strong BIEF effect, where the charge accumulates at the interface and subsequently migrates along the direction of the alternating electromagnetic field to promote the dissipation of EMW by polarization loss. However, an excessive number of interfaces leads to many carriers being bound by the interfaces, which is not conducive to forming electron channels. By coordinating the heterointerface states to achieve opti-mal EMW absorption performance, SZ-3 can accomplish an effective absorption width (EAB) of 5.93 GHz at a thickness of 1.91 mm. This work provides new ideas and methods for BIEF-based heterointerface engineering applied to EMW absorption materials.

Key words: Electromagnetic wave absorption, Heterointerface, Built-in electric field, Polarization loss, Interface state