Rational design of MXene/NiO/PPy ternary composites for bifunctional applications of microwave absorption and anticorrosion

The rapid advancement of 5G communication, radar detection, and marine engineering has intensified the dual challenges of electromagnetic interference and metal corrosion, necessitating materials that integrate high-performance microwave absorption with durable anticorrosion protection. However, traditional absorbing materials often suffer from high density, poor impedance matching, or inadequate corrosion resistance, while binary composites lack sufficient multifunctional synergy. Herein, we reported a ternary MXene-NiO-PPy composite engineered to overcome these limitations. Through in situ polymerization, we constructed a unique “sheet-wire” architecture where NiO nanowires and polypyrrole (PPy) coatings were uniformly anchored on MXene layers. Systematic investigation reveals that the composite with an MXene:NiO:PPy mass ratio of 1:1:0.75 exhibited superior microwave absorption, achieving a minimum reflection loss (RLmin) of − 36.80 dB at 16.16 GHz with a thickness of 7.6 mm. The enhanced absorption mainly originates from dielectric loss associated with conductive loss, interfacial polarization, and dipolar polarization, together with optimized impedance matching and multiple reflection effects within the heterogeneous network. In particular, NiO contributes mainly by constructing abundant heterogeneous interfaces and regulating the local dielectric environment, thereby promoting interfacial polarization and facilitating impedance matching. Meanwhile, when incorporated into waterborne epoxy (WEP) coatings at 1.5 wt% loading, the composite provided outstanding long-term corrosion resistance, as evidenced by a charge transfer resistance of 1.285 × 10 5 Ω·cm 2 after 60 days of immersion in 3.5 wt% NaCl solution. The enhanced protection is associated with the tortuous barrier effect of MXene, the passivation capability of PPy, and the structural reinforcement provided by NiO nanowires.