Synthesis and electrochemical investigation of polyaniline/unzipped carbon nanotube composites as electrode material in supercapacitors

• RUCNT was synthesized through thermal reduction of longitudinally unzipped MWCNT.
• PANI/RUCNT was synthesized by in situ chemical oxidative polymerization method.
• PANI/RUCNT-3 composite showed the highest specific capacitance of 762 Fg−1.
• Specific capacitance of PANI/RUCNT-3 is about 2.58 times that of the raw PANI.
• PANI/RUCNT-3 showed the best capacitance retention among the other PANI composites.

In this research, polyaniline (PANI)/unzipped carbon nanotube (UCNT) composites were synthesized by in situ chemical oxidative polymerization method. The UCNTs were synthesized via longitudinal unzipping of multi-walled CNTs (MWCNTs) through chemical treatments. Different unzipping levels in UCNTs were obtained by regulating the introduced amount of oxidant (KMnO4) into reaction solutions. Transmission electron microscopy, scanning electron microscopy, Raman spectroscopy and X-ray diffraction were applied in order to characterize the synthesized samples. Electrochemical properties of electrodes were studied by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy techniques in 1 M HCl aqueous solution. The electrochemical measurements of electrode materials confirmed that composition of PANI with the partially UCNT exhibited much higher specific capacitance (762 Fg−1) compared to the pure PANI (295 Fg−1) at a scan rate of 30 mV s−1. In addition, this composite electrode showed better cycling stability with 81% capacitance retention after 1000 cycles. These improvements could be mainly attributed to the presence of CNT/UCNT mixture in the composite structure, resulting from partially unzipping of CNTs, which greatly facilitates electrolyte ions accessibility to the electrode material during charge/discharge process and also maintains the mechanical strength. These results can introduce PANI/UCNT composite as a promising electrode material for supercapacitor applications.

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