Pd-mellitic acid ligand-induced uniform FeCoNiCuPd HEA nanoparticles anchored on hollow carbon nanorods for ultra‑wideband electromagnetic wave absorption

High-entropy alloys (HEAs) are promising electromagnetic absorbers owing to tunable magneto-dielectric properties, yet severe particle agglomeration and grain coarsening severely degrade their wave-absorbing capacity. Herein, a Pd-mellitic acid ligand-induced strategy is developed to immobilize uniform FeCoNiCuPd quinary HEA nanoparticles on one-dimensional hollow mesoporous carbon nanorods (CPMO@5 A). Multidentate carboxyl groups of mellitic acid serve as universal coordination sites for synchronous multi-metal nucleation, effectively restraining HEA aggregation and triggering prominent grain refinement and lattice distortion driven by high configurational entropy. Benefiting from hierarchical porous architecture, uniform-dispersed HEA nanoparticles and abundant heterogeneous crystal defects, CPMO@5 A achieves superior electromagnetic wave absorption. It delivers a minimum reflection loss of −76.6 dB at 2.7 mm and an ultra-wide effective absorption bandwidth of 8.4 GHz, covering the entire Ku-band and most X-band. Meanwhile, it exhibits infrared absorptivities of 98.2%, 98.9% and 97.7% in long-wave, mid-wave and short-wave infrared regions, outperforming most reported HEA absorbers. Dielectric loss from Cu and carbon matrix, coupled with magnetic loss of Fe, Co, Ni and Pd, synergistically promotes electromagnetic energy dissipation. This work provides a facile universal route for fabricating HEA-based electromagnetic materials for high-performance radar-infrared compatible stealth materials.