One of the promising supercapacitors for next-generation energy storage is zinc-ion hybrid supercapacitors. For the anode materials of the hybrid supercapacitors, three-dimensional (3D) graphene frameworks are promising electrode materials for electrochemical capacitors due to their intrinsic interconnectivity, excellent electrical conductivity, and high specific surface area. However, the traditional route by which 3D graphene frameworks are synthesized is energy- and time-intensive and difficult to apply on a large scale due to environmental risks. Here, we describe a simple, economical, and scalable method of fabricating grafoil (GF) directly into a graphite–graphene architecture. Both synthesizing of a porous structure and functionalization with interconnected graphene sheets can be simultaneously achieved using electrochemically modified graphite. The resultant graphite electrode provides a high capacitance of 140 mF/cm2 at 1 mA/cm2, 3.5 times higher than that of pristine grafoil, keeping 60.1% of its capacitance when the current density increases from 1 to 10 mA/cm2. Thus, the method to produce 3D graphene-based electrodes introduced in the current study is promising for the applications of energy storage devices.

    Abstract
    1 Introduction
    2 Experimental
        2.1 Materials
        2.2 Electrochemical modification of grafoil
        2.3 EMG characterization
        2.4 Electrochemical measurements
    3 Results and discussion
    4 Conclusions
    References

• Yeon Ju Kwon(C1 Gas & Carbon Convergent Research Center, Korea Research Institute of Chemical Technology (KRICT), School of Chemical Engineering, Sungkyunkwan University (SKKU))
• Ho Seok Park( School of Chemical Engineering, Sungkyunkwan University (SKKU))
• Young‑Pyo Jeon(C1 Gas & Carbon Convergent Research Center, Korea Research Institute of Chemical Technology (KRICT))