Bifunctional Cu9S5/C octahedral composites for electromagnetic wave absorption and supercapacitor applications

[Display omitted] •The octahedral Cu9S5/C composites derived from HKUST-1 are synthesized.•Multiple loss mechanisms result in superb electromagnetic wave absorption.•Polarization behavior is analyzed by simulating the electric field distribution.•The composites exhibit prominent specific capacitance and rate capability. Rational component configuration and microstructure design are critical for both electromagnetic wave absorption (EMA) and supercapacitor materials. Herein, the hierarchical Cu9S5/C composites derived from metal-organic frameworks (MOFs) are fabricated for both EMA and supercapacitor applications. The composites are assembled with Cu9S5 nanoparticles uniformly embedding on the surface and inside of the octahedral carbon skeleton. Combination of the two components endows the composites with adjustable electromagnetic parameters, thus achieving favorable impedance matching and dielectric loss capability. With the assistance of electric field simulation, the dielectric loss behavior is in-depth analyzed. The Cu9S5/C composites achieve an optimized absorption intensity of −62.3 dB at 1.3 mm and a broad effective absorption bandwidth (EAB) of 4.7 GHz. Intriguingly, benefiting from the elaborate configuration that the highly electrochemically active Cu9S5 nanoparticles embedded in highly conductive carbon skeleton, the composites also deliver prominent electrochemical performance as supercapacitor anode material, with the specific capacitance of 1323.6 F g−1 at 1 A g−1, rate capability of 72.0% retention at 20 A g−1, and 88.8% capacity retention after 5000 cycles. This work enriches the application trials of MOF-derived sulfide/carbon composite materials as multifunctional materials.