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.