Hybrid composite of nitrogen functionalized graphene–polyaniline electrode for high performance supercapacitor

Abstract

Polyaniline (PANI) hybrid composite was prepared with nitrogen-functionalized graphene (NFG) via in situ polymerization of aniline in the presence of NFG for supercapacitor electrodes. Nitrogen functionalized graphene–polyaniline composite (NFGP) was used as an electrode in a symmetric supercapacitor cell configuration and its performance was evaluated by cyclic voltammetry, charge–discharge and electrochemical impedance spectroscopy measurements. The electrochemical performance of NFGP are compared with its constituents of NFG, PANI and also with hydrothermally treated graphene oxide (HTGO). Electrochemical capacitance of PANI (350 F g⁻¹) increased with increases in the amount of NFG, attained a maximum with 5 wt% of NFG (383 F g⁻¹) and then decreased with further increase of NFG. PANI with 5 wt% NFG showed a high discharge capacitance value of 383 F g⁻¹ with an energy density of 19 W h kg⁻¹ at a power density of 200 W kg⁻¹. The initial capacitance value of the NFGP5 cell decreased to 253 F g⁻¹ for up to 700 charge–discharge cycles and then almost remained constant for up to 33 000 cycles (∼240 F g⁻¹). Moreover, the NFGP5 electrode showed a very low ESR value (0.6 Ω), low time constant (0.1 ms) and phase angle (82°) close to that of ideal capacitor value of 90°. The NFGP5 sample was thermally stable up to 250 °C. Hydrophilicity of NFGP5 was higher compared to that of PANI. Morphological analysis revealed the uniform distribution of PANI on the surface of NFG, indicating a strong interaction between them.