Plastic pollution and water hyacinths consistently co-occur in the lower Saigon river

Abstract

Graphene/polyaniline composite hydrogels (GH/PANI) were chemically synthesized by in situ polymerization of aniline monomer. Graphene hydrogels were obtained by a hydrothermal method and used in supercapacitors. The graphene/polyaniline composite hydrogel exhibits better electrochemical performance than the pure individual components as determined by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopic (EIS) measurements. A remarkable specific capacitance (Csp) of 323.9 F g-1 was measured using cyclic voltammetry at a scan rate of 2 mV s-1 at 25 oC. GCD measurements (311.3 F g-1) and electrochemical impedance analysis also support these results. The numbers were obtained at extremely high loading masses: 7.14 mg cm-2 for GH and GH/PANI synthesized at 0 oC, and 8.93 mg cm-2 for GH/PANI synthesized at 25 oC. The corresponding areal capacitances are 1.14, 1.75 and 2.78 F cm-2 for GH, and GH/PANI composite hydrogels synthesized at 0 oC and 25 oC, respectively. These values in F cm-2 are 3.80, 5.83 and 9.27 times higher than commercially available activated carbon supercapacitors (~0.3 F cm-2 for a two electrode system). Moreover, the GH/PANI composite synthesized at 25 oC exhibits excellent stability with 99% initial capacitance retention after 1000 charge/discharge cycles. GH/PANI composites synthesized at 0 oC and 25 oC therefore hold promise for use in supercapacitor device applications.