High‐Entropy‐Inspired Multiple Non‐Metallic Doping Porous Carbon Fiber for Broadband and Environmentally Stable Microwave Absorption

ABSTRACT Advanced microwave absorption (MA) materials are urgently required to address the electromagnetic interference issues. Although carbon materials exhibit advantages in density and stability, their MA performance is critically limited in effective absorption band ( EAB ). High‐entropy (HE) doping is a feasible strategy to realize broadband absorption, but research has mainly focused on alloys and oxides. Herein, we introduce the concept of high‐entropy engineering into the synthesis of carbon fibers (CF) featuring six non‐metal elements (N, O, S, P, B, and F) for broadband and environmentally stable MA. The multi‐element heteroatoms with various electronegativities disrupt the local sp 2 ‐conjugated graphene network and produce structural wrinkles across the graphene plane. These effects not only modulate the electrical conductivity but also aggravate the local charge imbalance of the CFs. The impedance match is optimized and the polarization relaxation loss is enhanced. With only 10 wt.% filling, the sample exhibits a strong minimum reflection loss ( RL min ) of ‐51.32 dB at 2.2 mm and a EAB of 6.05 GHz at 2.0 mm. More importantly, the fibers exhibit stable MA performance even after long‐term high‐temperature, low‐temperature, and ultraviolet aging. This work presents an effective high‐entropy‐inspired design for carbon‐based MA materials.