Three-dimensional design and fabrication of reduced graphene oxide/polyaniline composite hydrogel electrodes for high performance electrochemical supercapacitors

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 measurements. A remarkable specific capacitance (C-sp) of 323.9 F g(-1) was measured using CV at a scan rate of 2 mV s(-1) at 25 degrees C. 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 degrees C, and 8.93 mg cm(-2) for GH/PANI synthesized at 25 degrees C. 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 degrees C and 25 degrees C, respectively. These values in F cm(-2) are 3.80, 5.83 and 9.27 times higher than commercially available activated carbon supercapacitors (similar to 0.3 F cm(-2) for a two electrode system). Moreover, the GH/PANI composite synthesized at 25 degrees C exhibits excellent stability with 99% initial capacitance retention after 1000 charge/discharge cycles. GH/PANI composites synthesized at 0 degrees C and 25 degrees C therefore hold promise for use in supercapacitor device applications.