Investigation of the electrochemical behavior of functionalized graphene by nitrophenyl groups as a potential electrode for supercapacitors

Abstract

In the present paper, graphene oxide (GO) has been synthesized using modified Hummer's method and then reduce by two separate procedures and functionalize. In the first method, GO is reduced to graphene (rGO) using hydrazine hydrate and functionalized by 4-nitrophenyl diazonium (4-NPD). In the second method, GO is reduced and functionalized simultaneously and in situ using 2,4-Dinitrophenylhydrazine (2,4-DNPH). Synthesized materials were structurally and chemically investigated by Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, thermal gravimetric analysis (TGA), BET measurement and scanning electron microscopy (SEM). Electrochemical and capacitive behavior of synthesized materials have been examined using cyclic voltammetry, galvanostatic charge/discharge, and impedance spectroscopy. The electrode made of functionalized graphene with 4-nitrophenyl diazonium salt (NP-rGO) shows a specific capacity of 178 F/g at a density of 0.1 A/g. Also, after 7000 charge cycles at a density of 3 A/g, capacity decreases 24% that shows acceptable stability for NP-rGO electrode. The electrode made of reduced and functionalized GO with 2,4-DNPH (DNPH-GO) shows a specific capacity of 169 F/g at a current density of 0.1 A/g and after 3000 charge and discharge cycles, at a current density of 3 A/g, retains 78% of its initial capacity.