Synthesis and in-situ functionalization of graphene films through graphite charging in aqueous Fe2(SO4)3

Low-cost synthesis and functionization of graphene is important for its application. Here, graphene and Fe3O4/graphene films were both prepared via a green approach of electrochemical exfoliation of graphite paper in aqueous Fe2(SO4)3. Iron ions in the electrolyte could facilitate graphite exfoliation and reduce hydrogen evolution in water medium as well as in-situ functionization of graphene. Small size (4–6 nm) of Fe3O4 uniformly grown onto graphene improved magnetic and electromagnetic properties as well as electrocatalytic activity of oxygen reduction reaction but decreased thermal conductivity and mechanical strength over free graphene. The films of 50 μm thickness of Fe3O4/graphene (21–58 wt% Fe3O4) exhibited excellent electromagnetic shielding of 41–62 dB at 1.0–18 GHz and good thermal conductivity (120 W/(m·K)), which may be related to their high electrical conductivity (500 S/cm) and ferromagnetism (241 Oe). Free-standing graphene films could reach high thermal conductivity of ∼787 W/(m·K) and electromagnetic shielding of 39–65 dB at 1.0–18 GHz as well as 48 MPa mechanical strength. Such competitive high performance of multi-functional graphene-based films holds a great potential in practical application.