N‑Doped Yolk–Shell\nCarbon Nanospheres\nwith “Carbon Bridges” for Supercapacitors

Abstract

N-doping\nmultilocular carbon spheres are beneficial to\nimproving\nthe electrical property due to their unique pore structure and elemental\ncomposition; nevertheless, there is a great challenge to fabricate\nthis structure in a facile way. In this work, an N-doping yolk–shell\ncarbon nanosphere with a “carbon bridges” structure\nwas prepared by domain-limited carbonization of RF@SiO₂ (RF = resorcinol-formaldehyde resin) with ethylenediamine (EDA)\nas the nitrogen precursor. The structure of the “carbon bridges”\nand the carbon shell’s thickness can be adjusted by controlling\nthe thickness of the silica layer, resulting in a change in morphology\n(from dense nanospheres to yolk–shell nanospheres). The optimized\nyolk–shell carbon nanospheres (C@C-2 nanospheres) exhibited\nhigh N-doping, an abundant micro-mesoporous structure, and an optimum\n“carbon bridges” structure, contributing to a high-rate\ncapability in a supercapacitor, which was reflected in the energy\nstorage dynamics. Herein, C@C-2 nanospheres, as an electrode material\nfor supercapacitors, presented a reversible specific capacitance of\n373.3 F g^–1 at 0.5 A g^–1 in 2\nM KOH and retained a well-advanced capacitance retention capability\n(95.8%) at 4 A g^–1 for more than 10,000 cycles.\nThis work sheds light on an avenue to design high-performance porous\ncarbons for efficient energy storage.