Combination of liquid-phase exfoliation and hydrothermal method has progressed in recent years mainly on production of 2D materials. In this study, graphene was successfully synthesized via combinatorial of liquid-phase exfoliation and hydrothermal method with the aid of various conductive surfactants perylene-3, 4, 9, 10-tetracarboxylate (PTCA), lithium perylene-3, 4, 9, 10-tetracarboxylate (LiPTCA) and sodium perylene-3, 4, 9, 10-tetracarboxylate (NaPTCA). The effect of the lithium ( Li+) and sodium ( Na+) cations toward the efficiency of the graphene exfoliation process and its electrical properties was thoroughly investigated. Based on the characterization techniques, it is revealed that NaPTCA is the ideal conductive surfactant to exfoliate graphene sheets. X-ray diffraction spectra verified that the Na+ cation certainly can enhance the exfoliation process by expanding the interlayer spacing. The lateral size of the graphene sheets with Na-PTCA surfactant was the smallest (4.17 μm) as observed from SEM micrograph. The maximum concentration of the graphene yield was achieved up to 0.151 mgmL− 1 in NaPTCA surfactant alongside with excellent electrical conductivity of 746.27 Sm− 1 and relevant specific capacitance of 129 Fg− 1.

    Abstract
    1 Introduction
    2 Experimental section
        2.1 Materials
        2.2 Preparation of PTCA surfactant
        2.3 Preparation of hydrothermal liquid-phase exfoliated (LPE) graphene
        2.4 Characterization
        2.5 Electrochemical studies
    3 Results and discussion
        3.1 Scanning electron microscope (SEM)
        3.2 Energy-dispersive X-ray (EDX)
        3.3 EDX mapping
        3.4 X-ray diffraction analysis (XRD)
        3.5 UV–visible analysis
        3.6 I–V characteristics measurement
        3.7 X-ray photoelectron spectroscopy (XPS)
        3.8 FTIR analyses
        3.9 Cyclic voltammetry
    4 Discussion
    5 Conclusion
    Acknowledgements 
    References

• Nurin Jazlina Ahmad(Faculty of Applied Sciences, Universiti Teknologi MARA)
• Ruziana Mohamed(Faculty of Applied Sciences, Universiti Teknologi MARA, NANO‑SciTech Lab (NST), Centre for Functional Materials and Nanotechnology (FMN), Institute of Science (IOS), Universiti Teknologi MARA)
• Mohd Firdaus Malek(Faculty of Applied Sciences, Universiti Teknologi MARA, NANO‑SciTech Lab (NST), Centre for Functional Materials and Nanotechnology (FMN), Institute of Science (IOS), Universiti Teknologi MARA)
• Saedah Munirah Sanusi(Faculty of Applied Sciences, Universiti Teknologi MARA)
• Myzatul Azlyin Muhamad(Faculty of Applied Sciences, Universiti Teknologi MARA)
• Ahmad Syakirin Ismail(MIMOS Semiconductor Sdn Bhd, Technology Park Malaysia)
• Mohamad Rusop Mahmood(NANO‑SciTech Lab (NST), Centre for Functional Materials and Nanotechnology (FMN), Institute of Science (IOS), Universiti Teknologi MARA, NANO‑ElecTronic Centre (NET), Faculty of Electrical Engineering, Universiti Teknologi MARA)