N-Doped Yolk–Shell Carbon Nanospheres with “Carbon Bridges” for Supercapacitors

Abstract

N-doping multilocular carbon spheres are beneficial to improving the electrical property due to their unique pore structure and elemental composition; nevertheless, there is a great challenge to fabricate this structure in a facile way. In this work, an N-doping yolk–shell carbon nanosphere with a “carbon bridges” structure was prepared by domain-limited carbonization of RF@SiO2 (RF = resorcinol-formaldehyde resin) with ethylenediamine (EDA) as the nitrogen precursor. The structure of the “carbon bridges” and the carbon shell’s thickness can be adjusted by controlling the thickness of the silica layer, resulting in a change in morphology (from dense nanospheres to yolk–shell nanospheres). The optimized yolk–shell carbon nanospheres (C@C-2 nanospheres) exhibited high N-doping, an abundant micro-mesoporous structure, and an optimum “carbon bridges” structure, contributing to a high-rate capability in a supercapacitor, which was reflected in the energy storage dynamics. Herein, C@C-2 nanospheres, as an electrode material for supercapacitors, presented a reversible specific capacitance of 373.3 F g–1 at 0.5 A g–1 in 2 M KOH and retained a well-advanced capacitance retention capability (95.8%) at 4 A g–1 for more than 10,000 cycles. This work sheds light on an avenue to design high-performance porous carbons for efficient energy storage.