Modified graphene papers with alkaline earth metal ions endowed with high heat transfer properties

• The graphene oxide paper is prepared through a facile vacuum filtration.
• The graphene paper is obtained by reduction of graphene oxide paper.
• The graphene paper is modified with alkaline earth metal ions.
• The modified graphene paper exhibits high thermal conductivity.
• The ion chelating can decrease thermal resistance and increase contact surface.

Graphene papers (GP) modified with alkaline earth metal ions (Mg2 +, Ca2 +) were prepared by reduction of graphene oxide papers, which were obtained through a facile vacuum filtration of graphene oxide solution aqueous. The thermal conductive properties of graphene paper and its modified analogues were measured with a laser flash method. The thermal diffusivities of Mg-modified GP and Ca-modified GP are 1003.4 mm2/s and 2232.2 mm2/s, respectively, which is significantly improved compared with unmodified graphene paper (694.9 mm2/s). The corresponding thermal conductivities are 100.4 W/mK (GP), 147.7 W/mK (Mg-GP) and 331.8 W/mK (Ca-GP), respectively, from which a substantial enhancement in thermal conductivity of M-modified GP is also observed. It is found that the ion chelating between carboxyl groups of graphene oxide and alkaline earth metal ions will bridge the small graphene oxide sheets, and it will decrease the thermal resistance of the boundary and increase the contact surface of graphene sheets. The reduction of M-modified graphene oxide can partly recover the structure of graphene, thus can further improve the heat transfer property of graphene paper.