| Summary: | Interfacial polarization is generally a major cause of dielectric loss, but its exact contribution to the electromagnetic wave (EMW) absorption capacity of absorbers remains to be elucidated. In this work, SnO<sub>2</sub>@rGO composite (S2) with tight interfaces formed by chemical bonds and SnO<sub>2</sub>/rGO mixture (S3) were synthesized by a simple chemical route followed by further calcined in argon, respectively. Compared with pure SnO<sub>2</sub> (S1) and S3, S2 exhibits much better EMW-dissipation ability, with a smaller minimum reflection loss (<i>RL<sub>min</sub></i>) value of −20.5 dB at a matched thickness of 5 mm and a larger effective absorption bandwidth (<i>f</i><sub>e</sub>) value of 5.8 GHz (from 11 GHz to 16.8 GHz) at 3.2 mm. By comprehensively comparing the defects, dipoles, and interfaces in S2 and S3, it is concluded that the excellent EMW absorption capacity of S2 is mainly caused by strong dielectric loss dominated by interfacial polarization as well as suitable impedance matching. This study provides an insight into the exact contribution of interfacial polarization to the EMW-dissipation ability of absorbers, showing that the EMW absorption of graphene-based composites can be effectively promoted by constructing well-connected interfaces between graphene and absorbers.
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