Tailoring sulfur/nitrogen co-doping configuration in MXene nanoribbon/nanosheet composite for high-performance electromagnetic wave absorption

Transition metal carbides (MXenes) used as electromagnetic wave absorption materials face two critical challenges: impedance mismatch caused by high conductivity and the easy restacking and agglomeration of ultrathin nanosheets. To address these issues, this study proposes the construction of an S/N co-doped MXene nanoribbon/nanosheet composite structure. An alkali-assisted chemical scissor strategy was used to successfully prepare a nanoribbon/nanosheet hybrid, which effectively suppressed nanosheet stacking and significantly increased the number of active interfaces and defect sites. By controlling the doping temperature, the doping configurations of S and N in MXenes can be precisely regulated, including lattice substitution (LS), functional group substitution (FS), and surface absorption (SA). With increasing doping temperature, the configuration of S/N dopants evolves from a combination of FS-type N and LS-type S to a coexistence of SA- and LS-type species. The former synergistically enhances conductive loss and polarization loss, whereas the latter suppresses electron transport and consequently reduces the complex permittivity of the material. The optimized composite exhibited considerably improved comprehensive electromagnetic wave-absorption performance at a low filler loading (10 wt%) and thin thickness (1.26 mm), achieving a minimum reflection loss (RL_min) of −53.77 dB and an effective absorption bandwidth (EAB) of 4.51 GHz. This work not only clarifies the regulatory mechanism of doping configurations on high-frequency electromagnetic properties but also provides a theoretical foundation for the rational design of high-performance MXene-based electromagnetic wave absorbing materials.