Figure 4

FE-SEM and TEM images of as-prepared N-S-G/Fe₃O₄ composite: (a) FE-SEM image of as-prepared N-S-G/Fe₃O₄ composite revealing the Fe₃O₄ nanoparticles encapsulated in the N, S co-doped graphene nanosheets; (b) high-magnification FE-SEM image of as-prepared N-S-G/Fe₃O₄ composite; (c) TEM image of as-prepared N-S-G/Fe₃O₄ composite indicating that there are many Fe₃O₄ nanoparticles distributed and encapsulated in the N, S co-doped graphene nanosheets (Fe₃O₄ nanoparticles with average diameters of ~5–10 nm are dispersed uniformly in in the N, S co-doped graphene nanosheets, as shown in the Inset); (d) high magnification TEM image of as-prepared N-S-G/Fe₃O₄ composite indicating that the Fe₃O₄ nanoparticles are effectively encapsulated into the N, S co-doped graphene nanosheets.