Systematic M-site engineering from Ti2CTx to (TiVNbHfTa)2CTx high-entropy MXenes for enhanced microwave absorption

High-entropy (HE) engineering presents a promising approach to optimizing the electromagnetic (EM) properties of MXenes for enhanced microwave absorption. In this study, a series of tunable configurational entropy MXenes Ti 2 CT x (MC-1), (Ti 1 / 2 V 1 / 2 ) 2 CT x (MC-2), (Ti 1 / 3 V 1 / 3 Nb 1 / 3 ) 2 CT x (MC-3), (Ti 1 / 4 V 1 / 4 Nb 1 / 4 Ta 1 / 4 ) 2 CT x (MC-4), and (Ti 1 / 5 V 1 / 5 Nb 1 / 5 Hf 1 / 5 Ta 1 / 5 ) 2 CT x (MC-5) are synthesized via selective etching and intercalation of their corresponding MAX phases. The structural and morphological characterization confirms the successful formation of accordion-like high-entropy MXenes. The electromagnetic evaluations demonstrate a significant enhancement in absorption performance corresponding to the increase in M-site entropy. The MXenes MC-4 and MC-5 also exhibit remarkably high performance, achieving minimum reflection losses (RL min ) of −48.5 dB at 8.56 GHz (2.85 mm) and −50.7 dB at 17.04 GHz (4.58 mm), along with effective absorption bandwidths (EAB) of 3.68 GHz and 1.92 GHz, respectively, surpassing their lower-entropy counterparts. Their superior stealth capabilities are further validated through radar cross section (RCS) simulations, which reveal that MC-4 and MC-5 coatings maintained RCS values below −20 dBm 2 across a broad angular spectrum (−60 to 60°), significantly outperforming a perfect electric conductor (PEC) baseline. This performance enhancement is essentially attributed to the entropy-mediated optimization of electromagnetic parameters, which improves impedance matching alongside intensified polarization loss resulting from lattice defects and interfaces. This study confirms that high-entropy design is an effective strategy for advancing high-performance wideband MXene absorbers, holding significant potential for applications in stealth and communication technologies.