Synthesis And Characterization Of N-doped Graphene By High-temperature Pyrolysis

Graphene, a two-dimensional single layer form of sp2-hybridized carbon atoms, has attracted more and more scientific attention because of its extraordinary properties and potential applications. Chemical doping N is considered an effective method to modify the energy band structure and properties of graphene, which is significant for graphene to expand its applications further. In this work, N-doped graphene(NG) was successfully synthesized by high-temperature pyrolysis route and examined in details. The main contents are as follows:1、NG was successfully synthesized through calcination of the mixture of dicyandiamide and glucose in an argon atmosphere. It is found that the synthetic approach can easily control the nitrogen doping level by adjusting the mass ratio X of dicyandiamide and glucose. The concentration of N atoms in NG samples is tuned from 22.44 at% to 17.77 at% with the mass ratio of dicyandiamide and glucose from 5 to 25. The three types of N atoms doped into the graphene network are Pyridinic N, Pyrrolic N and Graphitic N, respectively. The photoluminescence properties of the as-prepared NG were studied systematically. The results show that N-doping can quench its fluorescence and the quenching efficiency depends on the Graphitic N content.2、 NG was successfully synthesized through calcination of the mixture of melamine and glucose in an argon atmosphere. The result suggests that melamine plays both roles of template for the formation of the two-dimensional structures of graphene and N source for doping. The synthetic approach can easily control the nitrogen doping concentration by adjusting the mass ratio Y of melamine and glucose. When the mass ratio of Y varies from 10 to 40, the concentration of N atoms in NG samples correspondingly varies from 21.26 at% to 18.79 at%. The advantage of melamine than dicyandiamide used in the synthesis is higher productivity.3、The effect of pyrolysis temperature on the N doping concentration has been investigated with the fixed mass ratio 20 of melamine and glucose. It is found that the N doping concentration can be controlled by the pyrolysis temperature. When the pyrolysis temperature changes 700 ℃ to 900 ℃, the concentration of N atoms in NG samples vary from 33.32 at% to 10.87 at%. It is known that thermal stability of three N atoms in graphene is different, i.e. the thermal stability of Pyridinic N and Pyrrolic N is weaker than that of Graphitic N, which leads to their concentrations decrease with the increase of pyrolysis temperature, while Grahpitic N could keep a constant concentration in NG samples.In summary, the results reported here indicate that high-temperature pyrolysis is an effective route to achieve NG with controlled N-doping concentration, which would benefit the applications of graphene.