Hollow Co9S8 nanoparticles with carbon shells for wide-band and efficient microwave absorption

Aiming to obtain advanced microwave absorbing materials with high absorption efficiency, broad absorption bandwidth and low density, herein, a novel nanocomposite with irregular hollow nanostructure of Co9S8@C was successfully prepared via a soft template and annealing method. Due to the shrinkage process of the Co9S8 nanospheres by annealing, Co9S8 cores and carbon shells were easily obtained. Because of the unique microstructure with irregular outer shells and heterogeneous interfaces, improved polarization loss, multiple reflection loss as well as the impedance matching capability was achieved. As a result, greatly enhanced microwave absorption performance with a reflection loss (RL) of − 51.3 dB at 4.12 GHz, and effective absorption bandwidth (RL<−10 dB) of 5.44 GHz at a thickness of only 1.35 mm was obtained, suggesting the unique Co9S8@C nanocomposite in this work to be an intriguing and promising microwave absorber.