Supercapacitive and ORR performances of nitrogen-doped hollow carbon spheres pyrolyzed from polystyrene@polypyrrole-polyaniline

Nitrogen-doped hollow carbon spheres (NHCSs) derived from polystyrene@polypyrrole-polyaniline (PS@PPY-PANI) core-shell composite microspheres of large surface area with improved electrochemistry performances have been effectively prepared and characterized systematically. NHCSs exhibited exceptional electrochemical properties with a maximum specific capacitance of 294.9 F g(-1) at a 5 mVs(-1) with good cycling stability of 95% after 5000 cycles at 0.5 A g(-1). It also showed enhanced oxygen reduction reaction (ORR) activity with a high onset potential of 0.83 V vs. RHE at 1600 rpm via the more favorable four-electron pathway in an alkaline medium. Enhanced electrochemical and electrocatalytic performances could arise from the hollow porous spherical structure, high surface area, and considerable pyrrolic-pyridinic nitrogen contents. Pyrolysis commences the incorporation of nitrogen units together with the high degree of graphitization which contributes exceptionally to improve the ion/charge transfers. Significantly, the synergistic effect of pyrolysis and the proper concentration of PPY-PANI improve the overall electrochemistry performances of NHCSs. The excellent cyclic stability, high specific capacitance, and exceptional ORR activity indicate its perspective as an efficient electrode material for supercapacitors and fuel cells. (C) 2019 Elsevier B.V. All rights reserved.