Electrostatic self-assembled CS/Ti₃C₂T_x/Co@CNT composites with gradient carbon structure and wideband microwave absorption

Two-dimensional MXene absorbing materials with excellent electrical conductivity and abundant surface functional groups make it potentially application in electromagnetic compatibility (EMC) for 5G communication and integrated circuit chip. However, the impedance mismatch caused by high conductivity would deteriorate the electromagnetic wave absorption performance of MXenes. In this work, a lightweight electromagnetic wave-absorbing material of CS/Ti₃C₂T_x/Co@CNTs with a gradient-dimensional structure was prepared using the positive-negative charge self-assembly method. The results shown that the heterogeneous interfaces of Co-CNTs, CNT-Ti₃C₂T_x and Ti₃C₂T_x-CS could be formed. At the same time, the porous network of carbon skeleton effectively reduces the density of Ti₃C₂T_x and generates the cobalt-CNTs structure, which ultimately improves the surface impedance of Ti₃C₂T_x. Therefore, CS/Ti₃C₂T_x/Co@CNTs composite could obtain the minimum reflection loss (RL_min) of −55.01 dB at the thickness of 3.4 mm and the effective absorption bandwidth (EAB) could reach 9.07 GHz. It should be emphasized that the average density of CS/Ti₃C₂T_x/Co@CNTs is only 0.03 g/cm³. The electrostatic self-assembled CS/Ti₃C₂T_x/Co@CNT composites behaved the excellent conductive loss, polar loss and the impedance matching. This work provides valuable insights into the exploration of lightweight wave-absorbing materials covering ultra-wide bands.