A novel kind of self-assembled graphene quantum dots-Co3O4 (GQDs-Co3O4) nanocomposite was successfully manufactured through a hydrothermal approach and used as an extremely effectual oxygen evolution reaction (OER) electrocatalyst. The characterization of morphology with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that Co3O4 nanosheets combined with graphene quantum dots (GQDs) had a new type of hexagonal lamellar selfassembly structure. The GQDs-Co3O4 electrocatalyst showed enhanced electrochemical catalytic properties in an alkaline solution. The start potential of the OER was 0.543 V (vs SCE) in 1 M KOH solution, and 0.577 V (vs SCE) in 0.1 M KOH solution correspondingly. The current density of 10 mA cm− 2 had been attained at the overpotential of 321 mV in 1 M KOH solution and 450 mV in 0.1 M KOH solution. Furthermore, the current density can reach 171 mA cm− 2 in 1 M KOH solution and 21.4 mA cm− 2 in 0.1 M KOH solution at 0.8 V. Moreover, the GQDs-Co3O4 nanocomposite also maintained an ideal constancy in an alkaline solution with only a small deterioration of the activity (7%) compared with the original value after repeating potential cycling for 1000 cycles.

Self-assembled graphene quantum dots-Co3O4 nanocomposite for highly efficient oxygen evolution reaction electrocatalyst
    Abstract
    1 Introduction
    2 Experimental
        2.1 Materials
        2.2 Preparation of graphene oxide
        2.3 Preparation of Co3O4
        2.4 Synthesis of self-assembled GQDs-Co3O4 nanocomposite
        2.5 Process of electrochemical measurements
    3 Results and discussion
        3.1 The characterization of the Co3O4 and self-assembled GQDs-Co3O4 nanocomposite
        3.2 Self-assembled morphological exploration
        3.3 Electrochemical performance
    4 Conclusions
    Anchor 15
    Acknowledgements 
    References

• Ruibin Guo(College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070, China)
• Mengqi Fang(College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070, China)
• Qianglong Chen(College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070, China)
• Nan Wang(College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070, China)
• Bingjie Wang(College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070, China)
• Nijuan Liu(College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070, China)
• Zunli Mo(College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070, China)