Balancing MXene Surface Termination and Interlayer Spacing Enables Superior Microwave Absorption

Abstract Surface chemistry and interlayer engineering determines the electrical properties of 2D MXene. However, it remains challenging to regulate the surface and interfacial chemistry of MXene simultaneously. Herein, simultaneous modulation of Ti 3 C 2 T x MXene surface termination and layer spacing by alkali treatment are achieved. The electrical and electromagnetic properties of Ti 3 C 2 T x are investigated in detail with respect to KOH and ammonia concentration dependence. A high concentration of KOH caused the Ti 3 C 2 T x layer spacing to expand to 13.7 Å and the surface O/F ratio to increase to 33.84. Because of its weaker ionization effect, ammonia provides finer tuning compared to the drastic intercalation of KOH with a thorough sweeping of the F‐containing groups. Ti 3 C 2 T x is enriched with conductive ‐OH termination after ammonia treatment, which achieves an effective balance with the increased interlayer resistance. Therefore, NH 3 H 2 O‐Ti 3 C 2 T x achieves broad‐band impedance matching and exhibits an efficient microwave loss of −49.1 dB at a low thickness of 1.7 mm, with an effective frequency bandwidth of 3.9 GHz. The results herein optimize the electrical properties of Ti 3 C 2 T x using surface and interfacial chemistry to achieve broad microwave absorption, providing a framework for enhancing the electromagnetic wave loss of intrinsic MXene.