Mechanochemical preparation of polydiphenylamine and its electrochemical performance in hybrid supercapacitors

Highlights: → For the first time, a simple to adopt, greener, rapid and efficient alternative route was successfully developed for preparing different PDPA salts. → For the first time, a judicial attempt was made to evaluate the performance of mechanochemically prepared PDPA-H2SO4 as cathode material in asymmetric hybrid supercapacitors. → The results obtained are highly promising and the physicochemical properties of PDPA salts could be fine-tuned in the future for large scale applications in energy storage devices. - Abstract: A simple mechanochemical route for the synthesis of high quality inorganic anion doped polydiphenylamines (PDPAs) is reported in this article. Elemental analysis performed for the PDPAs indicated the presence of dopant anions in the polymeric chain. PDPA prepared in the presence of 96 wt% H2SO4 (PDPA-H2SO4) was found to be better doped than the other polymeric salts. Spectroscopic profiles of the polymers showed that the PDPAs were in a doped conducting state. The X-ray diffraction (XRD) pattern of the as-prepared polymeric powders revealed the presence of more crystalline phases in PDPA-H2SO4. Field emission scanning electron microscopic (FESEM) images highlighted the formation of inorganic anion doped PDPA particles with different sizes (80-100 nm). Electrochemical studies performed for the polymeric particles depicted the redox behavior and good electrochemical activity of PDPA salts. Thermogravimetric analysis (TGA)/differential thermal analysis (DTA) proved that all the PDPA salts were thermally stable up to 300 deg. C. The electrochemical performance of PDPA-H2SO4 in hybrid supercapacitors was evaluated due to its superior physicochemical properties. The maximum specific capacitance of the hybrid supercapacitor constructed out of PDPA-H2SO4 powder was found to be 108 F g-1.