Growing CoNi nanoalloy@N-doped carbon nanotubes on MXene sheets for excellent microwave absorption.

• 0D CoNi nanoalloy-encapsulated 1D NCNT were grown on 2D Ti 3 C 2 T x sheets. • High surface areas and excellent thermal oxidation stabilities were achieved for the composite. • The minimum RL reached −55.3 dB at 2.1 mm. • The EAB of 4.3 GHz at 1.5 mm could be attained. Recently, two-dimensional MXene materials have attracted numerous attention in electromagnetic wave shielding/absorption. Hybridizing magnetic materials and constructing multi-dimensional structures in MXene is highly beneficial to improve electromagnetic wave absorption properties. Herein, we demonstrate a strategy for in situ growing 0D CoNi nanoalloy-encapsulated 1D N-doped carbon nanotubes on a 2D Ti 3 C 2 T x MXene sheet through an electrostatic assembly process followed by a high-temperature pyrolysis process. The resultant 201-structured MXene-CoNi@N-doped carbon nanotube (MXene-CoNi@NCNT) composites displayed high surface areas (55.6–103.7 m²/g), moderate magnetism (19.8–24.6 emu/g), and excellent thermal oxidation stabilities (≥ 307 °C). In addition, the unique 2D/0D/1D architectures entrusted the composites with abundant interfaces, various defects, and numerous nitrogen dopants. Taking advantage of the special 201 structure and the existence of both magnetic and dielectric loss, the MXene-CoNi@NCNT composite showed great impedance matching and strong attenuation performance. A strong reflection loss of –55.3 dB was achieved when the coating thickness was 2.1 mm, and a wide effective absorption bandwidth of 4.3 GHz was achieved at a thickness of 1.5 mm, much superior to that of similar absorbers. This work demonstrates a novel strategy for designing electromagnetic wave absorbers with magnetic and dielectric losses accompanied by multiple dimensional structures. [ABSTRACT FROM AUTHOR]