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A polyaniline (PANi)-carbon quantum dots (CQDs) nanocomposite material with CQDs made from a PEG (polyethylene glycol and NaOH) source was synthesized. This unique synthesis technique was developed to overcome the setbacks of the PEG method by using UG (urea and glycine). PANi was synthesized by chemical oxidation in the presence of CQDs, which were prepared according to the two above-mentioned methods. The sample was further characterized by morphological, optical, and electrochemical experiments. FE-SEM showed ridge-like morphology and UV-Vis studies revealed the presence of PANi and CQDs. HRTEM images gave details on the uniformly distributed polyaniline, which showed lengthy rod-like rough surfaces with interconnected tiny CQDs. The electrochemical results from CV and GCD studies indicated an enhancement of the specific capacitance for sample PCQ-2 (CQDs synthesized via the UG method as a source) compared to only PANi and PCQ-1 (CQDs prepared by the PEG method). The cyclic stability established was 84.5% retention from initial capacitance values over 3000 cycles. A two-electrode prototype device was also developed with the PCQ-2 sample and it achieved a reasonable capacitance of 161.3 mF/cm2 and demonstrated good retention stability over 5000 cycles. These results may be due to a variety of factors related to compositing CQDs (with urea and glycine as a source) with PANi.

Herein, we have reported fully organic acid doped polyaniline nanotube as a metal free electrode material for supercapacitor device fabrication. The energy storage behavior of this polymer greatly depends with morphology of nanostructure that has been optimized by using different number of carboxylic groups functionalized organic acid like benzene dicarboxylic acids (OA2), benzene tricarboxylic acids (OA3) and benzene tetracarboxylic acids (OA4). Prepared nanostructures were characterized by UV–Vis, XRD, FTIR, FESEM and HRTEM. Importantly, the charge storage properties of nanostructure were studied by Cyclic voltammetry (CV), galvanic charge discharge (GCD) and electrochemical impedance spectroscopy (EIS). It has been noticed that benzene tetracarboxylic acids (OA4) doped polyaniline (OA4PAN) is the optimum nanostructure having specific capacitance ~ 400 F/g at 0.5 A/g in the three-electrode system. A symmetrical solid-state device with excellent mechanical flexibility has been fabricated with optimized nanostructure revealed the specific capacitance of 107 F/g at a 0.2 A/g in wide potential window with high cyclic stability up to 5000 cycle at 2 A/g (~91% retention of specific capacitance). This nanostructure could be eligible to use for various energy storage system in near future.

Herein, we have developed a simple and facile technique at 210 °C to obtain nano-structured organic compounds, instead of making carbon dots at a relatively higher temperature. Taking the advantage of stable dispersion of organic nanostructures in an aqueous medium, composite of polyaniline has been developed and subsequently utilized as an active electrode material for supercapacitor application. This composite material confirms noteworthy enhancement in specific capacitance (779 F/g) and also divulges the attractive capacitance retention using three-electrode systems. The suitability of the materials for the solid-state device was tested with a prototype two-electrode device. The symmetric device exhibits 130 F/g gravimetric capacitance and 650 mF/cm2 areal capacitance. The improved performance in the specific capacitance is observed due to the generation of more active charge storage sites in the interfacial interaction of organic nanostructures and polyaniline in the composite. The cyclic stability of the symmetric device reveals excellent retention of 96% in specific capacitance over 5000 cycles.