Homogeneous-heterogeneous interfaces in 2D/2D CoAl/Co9S8/Ni3S4 heterostructures for electromagnetic wave absorption

Exploring electromagnetic wave (EMW) absorbers with ultrathin matching thickness (d < 1.5 mm), strong reflection loss (RL < -50 dB), and wide effective absorption bandwidth (EAB, RL < -10 dB) is urgent and essential for reducing EMW radiation and interference. Herein, a 2D/2D CoAl/Co9S8/Ni3S4 heterostructure was constructured using simple hydrothermal and pyrolysis methods. 2D porous CoAl nanosheets and 2D Co9S8/Ni3S4 ultrathin nanosheets are assembled by small nanoparticle chains. Strikingly, the CoAl/Co9S8/Ni3S4 heterostructure exhibits remarkable EMW absorption performance with a RL value of -61.56 dB, a high EAB of 4 GHz, and an ultrathin matching thickness of 1.25 mm. Mechanism investigations reveal that the CoAl/Co9S8/Ni3S4 heterostructure delivers dual metal sulfides behavior, high specific surface area, strong interactions, rich defects (N doping), and abundant homogeneous and heterogeneous interfaces, which promote good impedance matching, dielectric loss (interface polarization, conductive loss, and dipole polarization), as well as magnetic loss (natural resonance, exchange resonance, and eddy current loss) characteristics. This work can provide insights into the mechanism of dual metal sulfides used as high-performance EMW absorbers and deepen our understanding of the design and application of 2D/2D heterostructures.