Boosting the supercapacitor performance of polyaniline nanofibers through sulfonic acid assisted oligomer assembly during seeding polymerization process

Abstract Polyaniline (PANI), thanks to low cost, easy synthesis, fast reversible Faradic reaction and especially theoretical charge storage capability, has been extensively studied in the field of energy conversion and storage. However, its development as electrode material in supercapacitor is still be restricted by the need of high–yield production of PANI with robust electrochemical performance. Herein, inspired by the seeding polymerization, and tunable conductivity and solubility with organic acid, one–pot bulk synthesis of PANI nanofibers in fully aqueous solution was realized with the aid of aniline oligomer and sulfonic acid. During the seeding polymerization process, four kinds of sulfonic acids with different functional groups and sizes including 5–sulfosalicylic acid (SSA), p–toluenesulfonic acid (pTSA), p–aminobenzenesulfonic acid (pASA) and camphorsulfonic acid (CSA) were introduced to efficiently control the assembly behavior of oligomers to form PANI nanofibers, meanwhile provide better electrical and electrochemical properties as well as good dispersion in aqueous solution compared with pure hydrochloric acid (HCl) medium. Benefiting from the bifunctional doping effects of sulfonic acid on the oligomer assembly and nanofiber dispersion, great enhancements on the electrochemical performances of PANI nanofibers can be easily achieved. Especially for CSA, high specific capacitance of 600.7 F g–1 at the current density of 1 A g–1 and good cycling stability with retention of 74% could be manifested, which are over 55% and 11% improvements in contrast to neat HCl medium, respectively. These results suggest that sulfonic acid assisted oligomer assembly is highly effective in combining smaller diameter of PANI nanofiber with superior supercapacitor property, and also provides a new strategy to promote the development of conductive polymers in energy related fields.