The reduced graphene oxide (rGO) has attracted more and more attention in recent years. How to choose a suitable reduction method to prepare rGO is a critical problem in the preparation of graphene composites. In this work, the differences of rGO reduced by thermal, microwave, Ultraviolet (UV) and reducing agent were studied. The reduction degree and functional groups of rGO were compared by SEM, XPS, Raman, FTIR and TGA. Thermal can remove most of the oxygen-containing groups of graphene oxide (GO) and the thermal reduction is the most effective reduction method. UV light can directly act on the unstable oxygen-containing groups, and its reduction efficiency is second only to thermal reduction. The efficiency of chemical reduction is not as good as that of UV reduction, because the reducing agent only act on the surface of GO. Microwave reduction is a mild thermal reduction with the lowest efficiency, but the residual oxygen-containing groups increase the hydrophilicity of rGO. To sum up, this work studies that rGO prepared by different reduction methods has different characteristics, which provides a reference for selecting appropriate reduction methods to prepare graphene composites with better properties.

    Abstract
        Graphic abstract
    1 Introduction
    2 Experimental
        2.1 Materials
        2.2 The preparation of T-rGO
        2.3 The preparation of M-rGO
        2.4 The preparation of P-rGO
        2.5 The preparation of C-rGO
        2.6 Characteristic of the rGO samples
    3 Results and discussion
    4 Conclusion
    Acknowledgements 
    References

• Xu Xiang(School of Materials Science and Engineering, Chongqing Jiaotong University)
• Ying Zhu(School of Materials Science and Engineering, Chongqing Jiaotong University)
• Changqin Gao(School of Materials Science and Engineering, Chongqing Jiaotong University)
• Han Du(School of Materials Science and Engineering, Chongqing Jiaotong University)
• Chunwen Guo(School of Materials Science and Engineering, Chongqing Jiaotong University)