Oxygen-sulfur Co-substitutional Fe@C nanocapsules for improving microwave absorption properties

Heteroatom substitution has been investigated to be a feasible way to optimize microwave absorption properties of core-shell structural nanocapsules at gigahertz. Although dielectric capacity has been increased at specific frequency with substituted absorbents, its broadband absorption performance is still relatively poor ascribed to the low dipole oscillation amplitude of single substituted heteroatom. In this study we demonstrate that sulfur and oxygen co-substituted heterostructure leads to high microwave absorption property of core-shell structural Fe@C nanocapsules at broadened frequency range, comparable to the single sulfur substitutional Fe@C nanocapsules. Experimental characterizations coupled with first-principles calculations reveal that the microwave absorption enhancement is triggered by the sulfur-oxygen co-substitution, which results in the serious symmetry breaking and thus leads to the charge separation at the co-substituted area. In particular, the nanocapsules exhibt the minimum reflection loss capcacity R(dB) of -52 dB at 6.8 GHz and the bandwith for R(dB) <-20 dB is in the frequency range of 3.1-12.7 GHz. The present study not only offers a deep insight into the relationship between heteroatom and microwave absorption property, but also puts forward a mentality for further designing microwave absorbents.