Constructing Built‑in Electric Fields With Flexible Heterointerface Engineering of MoO _3‐x /MXene for Electromagnetic Wave Absorption

ABSTRACT The development of high‐performance electromagnetic wave (EMW) absorption materials increasingly relies on the strategic design of multicomponent heterostructures. Herein, we constructed a flexible semiconductor/metal heterostructure consisting of oxygen‐vacancy‐engineered MoO 3‐x and MXene with metallic electrical conductivity. Leveraging van der Waals forces and hydrogen bonding, we integrated MoO 3‐x nanobelts with Ti 3 C 2 nanosheets to form stable and flexible films with tunable interfacial properties. This heterostructure induced a built‐in electric field (BIEF), significantly enhancing electron transfer. Experimental and theoretical analyses confirmed that the synergy of BIEF with oxygen vacancy defects, multi‐level scattering, and optimized conductivity drastically enhanced interfacial polarization and strengthened EMW attenuation. The optimized MoO 3‐x /2MXene composite exhibited superior EMW absorption, achieving a minimum reflection loss ( RL min ) of −62.7 dB at 7.8 GHz with an effective absorption bandwidth ( EAB ) of 6.8 GHz. These findings delivered critical insights on understanding and improving interfacial effects for EMW absorption, while also establishing a promising platform for the engineering of heterointerfaces in customized 2D flexible layered structures.