Cellulose Nanofiber/Mxene Nanosheet/Nickel Chain Composite Carbon Foams for Electromagnetic Wave Absorption

Developing composite carbon foams with multiple loss mechanisms and achieving stable and efficient electromagnetic wave absorption performance in harsh environments remain challenges. In this study, aqueous dispersions containing Ni²⁺ cellulose nanofiber (CNF) and Ti₃C₂T_x MXene were used to stabilize a styrene–butadiene–styrene (SBS) cyclohexane solution in the oil phase to form a Pickering emulsion gel. This gel was combined with freeze-drying and thermal annealing processes to synthesize nickel nanowires (Ni NWs) in situ within a three-dimensional pore structure at elevated temperatures, resulting in the production of C–CNF/MXene/Ni NW composite carbon foams. In this process, carbonized CNF and SBS function as three-dimensional scaffolds, while two-dimensional MXene sheets and in situ synthesized Ni NWs are uniformly integrated to establish a conductive network with heterogeneous interfaces. The resultant composite carbon foam demonstrates stable microwave absorption properties, with the C-C1M1N3 carbon foam achieving a minimum reflection loss (RL_min) of −45.2 dB at 13.6 GHz when the thickness is only 3.0 mm and a wide effective absorption bandwidth (EAB) of 7.6 GHz at the same thickness. Additionally, the carbon foam exhibited excellent hydrophobicity and lipophilicity, indicating potential for oil–water separation applications.