Sustainable\nSynthesis of Hierarchically Porous Hollow\nCarbon Spheres for Enhanced Zinc-Ion Hybrid Supercapacitors

Abstract

We\nhave developed an environmentally friendly and scalable method\nfor synthesizing hierarchically porous hollow carbon spheres (HCSs)\nas cathode materials for zinc-ion hybrid supercapacitors (ZISCs).\nThis method involves the sodium chloride (NaCl)-confined pyrolysis\nof polystyrene@polypyrrole nanoparticles. Unlike traditional methods,\nthis one-pot, chemical-recycling, molten salt-confined pyrolysis process\nwas conducted under an air atmosphere, eliminating the need for expensive\ninert gas protection. NaCl served as a noncorrosive barrier to isolate\nair during pyrolysis. The optimized HCSs possessed abundant hierarchical\npore structures, high specific surface areas (578.2 m² g^–1), and significant levels of oxygen (2.6 at %) and\nnitrogen (5.6 at %) doping. The HCSs exhibited a high specific capacitance\nof 108.7 F g^–1 in a three-electrode system with\na 6 M KOH electrolyte. Furthermore, ZISCs fabricated using HCSs as\ncathodes demonstrated an impressive energy density of 26.2 W h kg^–1 at a power density of 140.1 W kg^–1 in a 2 M ZnSO₄ electrolyte. These results highlight environmentally\nfabricated porous carbon materials and the potential application of\nHCSs as ideal carbon electrode materials for various electrochemical\nenergy storage devices.