Large-scale mechanical preparation of graphene containing nickel, nitrogen and oxygen dopants as supercapacitor electrode material

In this paper, graphite, melamine and transition metal salts with crystal water were used as raw materials to prepare atomic nickel, nitrogen and oxygen tri-doped graphene (NiNOG) as high-performance graphene-based supercapacitor electrode materials by a simple mechanical method (one-step ball milling). This method has the advantages of low cost and high efficiency with large-scale production. NiNOG has a large specific surface area and abundant functional groups containing oxygen and nitrogen atoms which can form coordination bonds with the atomic metal ions, making metal ions fully used in faradaic reaction. Besides, coordinate bond formed between N/O-containing groups and metal ions provides the materials with high conductivity and stability, resulting in an excellent pseudo-capacitance performance. The influence of the mass ratio of Ni(NO3)(2)center dot 6H(2)O/graphite and the amount of crystal water in the metal salts on the electrochemical properties of the product were also studied. When the mass ratio of Ni(NO3)(2)center dot 6H(2)O/graphite reached 1.5:1 and the crystal of transition metal salt contained six water molecules, the prepared compound (NiNOG-1.5) possessed a mass specific capacitance as high as 532 F g(-1) at 1 A g(-1) , excellent rate performance, and cycle stability. The asymmetric supercapacitor assembled with NiNOG-1.5 as the positive electrode and activated carbon as the negative electrode also showed bright application prospects. The work in this paper provides new ideas for the large-scale preparation of atomic metal ion-doped graphene and its application in energy storage devices.