Functionalized graphene oxide based on p-phenylenediamine as spacers and nitrogen dopants for high performance supercapacitors

p-Phenylenediamine (PPD) functionalized graphene oxide (GO) materials (PPDG) were prepared through a one-step solvothermal process and their application as supercapacitors (SCs) were studied. The PPD is not only as the spacers to prevent aggregating and restacking of the graphene sheets in the preparing process but also as nitrogen sources to obtain the nitrogen-doped graphene. The structures of PPDG were characterized by Fourier transformed infrared spectroscopy (FT-IR), X-ray diffraction spectroscopy (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) and the results show that the nitrogen-doped graphene was achieved with nitrogen content as high as 10.85 at.%. The field emission scanning electron microscopy (FE-SEM) and high resolution transmission electron microscopy (HR-TEM) have confirmed that the morphologies of PPDG were loose layered with less aggregation, indicating that PPD molecules, as spacers, effectively prevent the graphene sheets from restacking during the solvothermal reaction. The special loose textures make PPDG materials exhibit excellent electrochemical performance for symmetric SCs with superior specific capacitance (313 F/g at 0.1 A/g), rate capability and cycling stability. The present synthesis method is convenient and may have potential applications as ultrahigh performance SCs.