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

Transition metal carbides (MXenes) as electromagnetic wave absorption materials face two critical challenges of 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 a sulfur/nitrogen (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 active interfaces and defect sites. By controlling the doping temperature, precise regulation of the doping configurations of S and N elements in MXene is achieved, 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, while the latter suppresses electron transport and consequently reduces the complex permittivity of the material. The optimized composite exhibits considerably improved comprehensive electromagnetic wave-absorption performance at a low filler loading (10 wt%) and a 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 regulation 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.