Polymorphic Polypyrrole-Modified MXene Nanosheets for Broadband Microwave Absorption

The absorption of microwaves is significantly influenced by the structure of the absorber. Typically, the electromagnetic parameters can be adjusted by modifying the structure of the absorber. In this work, a novel approach is proposed to enhance microwave absorption properties by adjusting the impedance matching of MXene nanosheets. MXene/PPy hybrids with loose lamellar structure are synthesized through self-assembly of positively charged polypyrrole (PPy) and MXene nanosheets with negative charges, facilitated by electrostatic and hydrogen-bonding interactions. The impact of polymorphic PPy on the electromagnetic parameters and microwave absorption properties of MXene nanosheets is comprehensively explored. It is found that the addition of PPy with different morphologies can effectively tune the electromagnetic parameters of the MXene nanosheets. Particularly, the microwave absorption capabilities are significantly enhanced when PPy nanopaperclips are uniformly adsorbed on the surface of the MXene nanosheets. This enhancement is attributed to the favorable impedance match between PPy nanopaperclips and MXene nanosheets along with the exceptional attenuation capabilities of PPy. A minimum reflection loss (RLmin) of −47.85 dB is achieved at an ultrathin matched thickness of 1.6 mm, and the maximum effective absorption bandwidth (EABmax) is 5.01 GHz at 1.9 mm for the prepared MXene/PPy nanopaperclip hybrid with a filling rate of 20%. Furthermore, a bandwidth with 99% absorption efficiency of 15.4 GHz (2.4–18.0 GHz) can be attained when the thickness of the absorber ranges from 1.6 to 10.0 mm. It is anticipated that this work will provide valuable insights for the manufacture of high-performance microwave absorbers.