Facile synthesis of ultralight S-doped Co3O4 microflowers@reduced graphene oxide aerogels with defect and interface engineering for broadband electromagnetic wave absorption

The development of modern information technology has recently put forward higher requirements for the ingenious design of electromagnetic wave absorbing (EMA) materials with a broad bandwidth at a low filling ratio. Herein, three-dimensional (3D) S-doped Co3O4 microflowers@reduced graphene oxide (S-Co3O4@RGO) aerogels are successfully prepared by interface and defect engineering with superior EMA capability. The 3D structure with a high surface-to-volume ratio can effectively avoid the agglomeration of Co3O4 and enhance the RGO-Co3O4 heterointerfaces to implement multiple reflection mechanisms. The synergistic effect of atom and phase cross-hybridization can improve defect-induced polarization centres and coherent interface-induced interface polarization. Meanwhile, the defects located at the interface have more charge transfer to enhance interface polarization than that at the interior, which is first proposed and demonstrated by density functional theory (DFT) calculations. Thus, the minimal reflection loss value can reach -56.7 dB (3.6 mm, 5.44 GHz) and the maximum effective absorption bandwidth is 8.48 GHz (ranging from 9.28 to 17.76 GHz) at a matching thickness of 2.3 mm with a filling ratio of 5 wt%. This work opens a new pathway to synthesize electromagnetic wave absorbents with synergistic defect and interface induced polarization loss, and has tremendous potential for EMA applications.