Electronic Delocalization of Fe Atom–Cluster for Long-Term Stable Electromagnetic Wave Absorption in Marine Environments

Abstract High‐performance electromagnetic wave (EMW) absorbers with environmental adaptability are essential for advanced maritime stealth and electromagnetic protection. Herein, we design a synergistic absorber integrating Fe clusters (Fe AC ) and single atoms (Fe SA ) to tackle the issue of EMW attenuation under high-salinity and humidity marine conditions. First-principles calculations and experiments reveal that Fe AC and Fe SA anchored on a π ‐conjugated carbon support form a delocalized electronic space that enables long-range electronic interactions and multicenter synergistic coupling. This electronic synergy markedly strengthens conduction loss and dipolar polarization, delivering a minimum reflection loss of − 68.78 dB and an effective absorption bandwidth of 6.00 GHz at a low loading of 6 wt%. Notably, Fe AC exhibits a thermodynamically preferred adsorption toward Cl − , generating locally enriched negative‐charge regions that mitigate direct ionic attack on atomically dispersed Fe SA sites and thereby suppress corrosion-induced performance degradation. In addition, the absorber film demonstrates mechanical flexibility and thermal insulation, highlighting its potential for durable and high‐efficiency maritime EMW protection applications.