Electron Delocalization Engineering on 2D High‐Entropy Metal Oxides for Boosting Electromagnetic Wave Absorption

Abstract High‐entropy oxides (HEOs) hold great potential as electromagnetic absorption (EMA) materials due to their fascinating “cocktail” effect. However, its intrinsic poor dielectric loss hinders EMA capability, while the ingredient design can facilitate dielectric loss regulation, which is critically lacking. Herein, an electronic delocalization engineering that is motivated by metal elements modulation, is implemented on 2D spinel‐type HEOs, which enhances the dielectric loss. In the HEOs with coexisting Cu and Mn (CuMn‐HEOs), the electronic delocalization triggers the restructuring of transition metal valence states and generates abundant oxygen vacancies, which effectively adjust the dielectric loss. Due to the electronic delocalization and unique nanosheet structure, the CuMn‐HEOs exhibit markedly superior absorption performance to other HEOs without Cu and Mn coexisting. Among them, the (CrMnFeNiCu) 3 O 4 achieves a remarkable minimum reflection loss (RL min ) of −50.7 dB (1.94 mm) and a maximum effective absorption bandwidth (EAB max ) of 4.7 GHz. Moreover, through radar scattering cross‐section simulation and assembling HEOs with polyvinyl alcohol into a soft membrane, the practical application potential of CuMn‐HEOs has been proven. This work demonstrates the great potential of electronic delocalization engineering on improving the intrinsic electromagnetic loss capability of metal oxides and paves new insights for developing advanced EMA materials.