Green and facile synthesis of polyaniline/tannic acid/rGO composites for supercapacitor purpose

Polyaniline/reduced graphite oxide (PANI/rGO) composites own promising electrochemical properties. However, the toxicity of commonly used reducers for graphite oxide (GO) and the restacking of rGO greatly obstacle the further development of PANI/rGO composites. To solve these problems, in this study the eco-friendly tannic acid (TA) was used to produce rGO. The results of X-ray diffraction, thermogravimetric analysis, and Raman spectroscopy indicated that TA effectively reduced GO into rGO-TA, and the rGO-TA showed good dispersion stability. Subsequently, PANI/rGO-TA (1:0.1 by weight) composites were synthesized, and their cyclic voltammetric behaviors were studied. The PANI/rGO-TA-24 h composite, in which the rGO was reduced by TA with a sufficient reduction time of 24 h, showed larger specific surface area, a more homogeneous distribution of PANI on the surface of rGO, and higher specific capacitance than the PANI/rGO-HH composite, in which the rGO were produced by using hydrazine hydrate (HH) as reduction agent. Finally, a two-electrode symmetric supercapacitor using PANI/rGO-TA-24 h composite as electrodes was assembled. It exhibited a high energy density of 1.68 W h kg−1 and a high power density of 115 W kg−1 at a current density of 0.5 A g−1.