Ultrathin MoS₂ Nanosheets Encapsulated in Hollow Carbon Spheres: A Case of a Dielectric Absorber with Optimized Impedance for Efficient Microwave Absorption

A dielectric loss-type electromagnetic wave (EMW) absorber, especially over a broad frequency range, is important yet challenging. As the most typical dielectric attenuation absorber, carbon-based nanostructures were highly pursued and studied. However, their poor impedance-matching issues still exist. Here, to further optimize dielectric properties and enhance reflection loss, ultrathin MoS₂ nanosheets encapsulated in hollow carbon spheres (MoS₂@HCS) were prepared via a facile template method. The diameter and shell thickness of the as-prepared HCSs were ∼250 and ∼20 nm. The encapsulated MoS₂ nanosheets presented high dispersity and crystallinity. Compared to a pure HCS or MoS₂ absorber, MoS₂@HCS exhibited an optimized impedance characteristic, which can be attributed to the synergistic effects between HCSs (ensuring rapid electron transmission and compensating the low conductivity of MoS₂) and MoS₂ nanosheets (exposing sufficient numbers of active sites for polarizations and multi-reflection). Consequently, the MoS₂@HCS was endowed with -65 dB EMW attenuation ability under 2 mm and the effective attenuation bandwidth under -20 dB was ∼3.3 GHz over the K-band under 1.2 mm and ∼3.4 GHz over the Ka-band under merely 0.7 mm. These results suggested that the MoS₂@HCS is a promising dielectric absorber for practical applications. Meanwhile, this work introduces a facile and versatile strategy, which could in principle be extended to other transition metal sulfide@HCS for designing novel EMW absorbers.