One-step synthesis of NH2-graphene from in situ graphene-oxide reduction and its improved electrochemical properties

Graphene oxide (GO) is reduced and functionalized with primary amine by a one-pot solvothermal process using ethylene glycol as solvent and ammonia water as nitrogen precursor at 180 °C for 10 h. The reaction is featured by nucleophilic substitution of –COOH and C–O–C groups by the ammonia radicals. The presence of primary amine in graphene is identified by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and proton nuclear magnetic resonance spectra. The atomic ratio of N to C can be tuned within 2–10% by changing the ammonia water to GO weight ratio in the reaction system. The resulting amine modified graphene (NH2-G) is an excellent electrochemical material and up to 217.8 F/g high specific capacitance is measured on NH2-G electrode at a current density of 0.4 A/g, superior over commercially available GO, chemically reduced GO, activated carbon, and CNT. The as-prepared NH2-G shows excellent cycle stability, with negligible decrease of specific capacitance value after thousand cycles.