Enhancing the Low/Middle‐Frequency Electromagnetic Wave Absorption of Metal Sulfides through F− Regulation Engineering

Abstract Fluorine ion (F − ) regulation engineering rarely has been presented as a promising strategy for obtaining high‐performance electromagnetic wave (EMW) absorbing materials, and the related EMW attenuation mechanism has never been elucidated. Herein, a new F − regulation strategy is demonstrated for the first time, giving rise to broad low‐/middle‐frequency EMW attenuation by synergistically manipulating multiple factors, such as the morphology, composition, interface, defects, and conductivity. It is found that both the F − concentration and its introduction method (i.e., in situ or post‐treatment) are significant. Because of the in situ introduced heterointerfaces, the enriched defects, appropriate composition, and electronic conductivity, improvements in impedance matching and F − ‐regulated dielectric loss are simultaneously achieved. Accordingly, the optimized NiCo 2 S 4 /Co 1− x S/Co(OH)F composite delivered an effective absorption band of 6.03 GHz (4.57–10.60 GHz), which is five times higher than the pure counterpart, making it the only sulfide‐based absorber with a broad absorption feature toward the low frequency (from 4 GHz) with a small thickness (<3 mm) to date. In short, this work not only expounds on the unique roles of F − in chemical synthesis, microstructure design, and EMW absorption but also offers a viable strategy for solving the low‐/middle‐frequency EM interference issues through F − regulation engineering.