Nitrogen-doped hollow carbon spheres with tunable shell thickness for high-performance supercapacitors

Nitrogen-doped hollow carbon spheres (NHCSs) are well prepared by using Cu₂O microspheres as a hard template and 3-aminophenol formaldehyde resin polymer as carbon and nitrogen precursors. The thickness of the carbon shell can be easily controlled in the range of 15–84 nm by simply adjusting the weight ratios of the precursors to Cu₂O microspheres, and the Cu₂O templates can also be further reused. Physicochemical characterization demonstrates that the obtained NHCSs possess a well-developed hollow spherical structure, thin carbon shell and high nitrogen doping content. Due to these characteristics, when further utilized as electrodes for supercapacitors, the NHCSs with the carbon shell thickness of 15 nm show a high capacitance of 263.6 F g⁻¹ at 0.5 A g⁻¹, an outstanding rate performance of 122 F g⁻¹ at 20 A g⁻¹ and an excellent long-term cycling stability with only 9.8% loss after 1000 cycles at 5 A g⁻¹ in 6 M KOH aqueous electrolyte. This finding may push forward the development of carbon materials, exhibiting huge potential for electrochemical energy storage applications.

Nitrogen-doped hollow carbon spheres (NHCSs) are well prepared by using Cu₂O microspheres as a hard template and 3-aminophenol formaldehyde resin polymer as carbon and nitrogen precursors.

Facile Synthesis of Nitrogen-Doped Microporous Carbon Spheres for High Performance Symmetric Supercapacitors

Nitrogen-doped microporous carbon spheres (NMCSs) are successfully prepared via carbonization and KOH activation of phenol-formaldehyde resin polymer spheres synthesized by a facile and time-saving one-step hydrothermal strategy using triblock copolymer Pluronic F108 as a soft template under the Stöber-like method condition. The influence of the ethanol/water volume ratios and carbonation temperatures on the morphologies, pore structures and electrochemical performances of the prepared NMCSs are investigated systematically. The optimal NMCSs have a large specific surface area of 1517 m2 g- 1 with a pore volume of 0.8 cm3 g- 1. The X-ray photo-electron spectroscopy analysis reveals a suitable nitrogen-doped content of 2.6 at.%. The as-prepared NMCSs used as supercapacitor electrode materials exhibit an outstanding specific capacitance of 416 F g- 1 at a current density of 0.2 A g- 1, also it shows an excellent charge/discharge cycling stability with 96.9% capacitance retention after 10,000 cycles. The constructed symmetric supercapacitors using PVA/KOH as the gel electrolyte can deliver a specific capacitance of 60.6 F g- 1 at current density of 1 A g- 1. A maximum energy density of 21.5 Wh kg- 1 can be achieved at a power density of 800 W kg- 1, and the energy density still maintains 13.3 Wh kg- 1 even at a high power density of 16 kW kg- 1. The results suggest that this work can open up a facile and effective way to synthesize the NMCSs for electrode materials of high performance energy storage devices.