N-heterocycle-functionalized graphene oxide complexed with cobalt(II) as symmetric supercapacitor electrodes

Herein, 5-amino-substituted 1,10-phenanthroline-functionalized graphene oxide (N-FGO) was complexed with cobalt(II), and synthesized nanocomposite (N-FGO-Co nanocomposite) used in an actual symmetrical supercapacitor. First, the nanocomposite was analyzed by XPS, XRD, FT-IR, SEM, TEM, and BET. After structural characterization, electrochemical tests (CV, GCD, and EIS) in three-electrode systems were performed to investigate the electrochemical behavior of the nanocomposite. N-FGO-Co nanocomposite exhibits quasi-rectangular shape CV diagrams, triangular and symmetrical GCD diagrams, low resistance, and high stability. The results confirmed the ideal electrochemical behavior of this composite as the supercapacitor electrode. In three-electrode system, the specific capacitance of 512 and 541 F g−1 were calculated at current density of 1 A g−1 and scan rate of 5 mV s−1, respectively. Then, the nanocomposite was investigated as positive and negative electrodes in a symmetrical supercapacitor. The N-FGO-Co//N-FGO-Co system shows specific capacity of 268 and 266 F g−1 at current density of 0.5 A g−1 and the scan rate of 5 mV s−1, respectively. Also, two-electrode system has good specific energy/specific power. The retention capacitance of three- and two-electrode systems, after 5000 charge-discharge cycles, were measured as 95.2% and 93.9%, respectively. The results confirm the high potential of synthesized nanocomposite in the application of supercapacitor electrode.