Brine solution-driven synthesis of porous polyaniline for supercapacitor electrode application

Abstract

Increasing environmental and economic impacts has driven the need for development of inexpensive methodology for polymer nanostructure synthesis using non-toxic reagents. Herein, we report synthesis of porous polyaniline (PANI) by polymerization of aniline in brine (saturated sodium chloride) solution. The resulting polyaniline is highly porous, thus providing large surface area, which is a vital parameter for the significant improvement of supercapacitor performance. Brine solution acted as a pseudo-template for the formation of porous PANI, eliminating the need of organic solvents/acids and hard/soft templates. The porous PANI electrodes showed a high specific capacitance of 662 F/g, which is 2.5 times greater than that of conventional PANI. X-ray diffraction studies revealed an ordered nature of porous PANI chains as compared to conventional one, whereas their chemical nature is similar as confirmed by FTIR, and UV–visible spectroscopy. Polymerization reaction carried out at various concentration of NaCl solution helped to understand the evolution of porous morphology, based on which a plausible mechanism is proposed for formation of the porous polymer. Polymerization was also carried out in brine in the presence of other commercial acids like sulphuric and nitric acids, to demonstrate the versatility of using brine in polymerization. Effect of other saturated ionic medium such as KCl, Na2SO4 and non-ionic medium like glucose, on the polymerization reaction was also studied.