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Figure 1: Schematic diagram of the formation process of hollow carbon spheres
Figure 2 Characterization of hollow carbon spheres: (a) Scanning electron micrograph (b) Transmission electron micrograph (c) Infrared spectrum (d) N1s spectrum
Nitrogen-doped nano-carbon materials have become one of the hot spots in the international carbon materials field. This is mainly because nitrogen atoms are one valence electron more than carbon atoms. After nitrogen doping into the six-membered ring structure of graphite, pyridine, pyrrole, and graphite can be formed. Nitrogen-containing functional groups such as nitrogen and pyridine oxide can not only improve the surface chemical activity of nano-carbon materials, but also regulate their electronic structure. Among a large number of nano-carbon materials, hollow carbon spheres have low density, high specific surface area, and structural characteristics such as filling cavities, and have broad application prospects in fields such as drug delivery, nanoreactors, lithium batteries, and active enzyme immobilization. Hollow carbon spheres are generally prepared by chemical vapor deposition method, arc discharge method, hydrothermal method, and template method. The main disadvantages include size control, large shell thickness, rough surface, and low degree of graphitization.
The research team of Zhang Jian, a researcher of the New Energy Technology Institute of the Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, cooperated with the School of Chemistry and Pharmaceutical Engineering of Hebei University of Science and Technology to carry out systematic research work and proposed the template method for the preparation of nitrogen-doped carbon nanospheres by graphitizing ionic liquids. The new method uses a nitrogen-containing ionic liquid as a carbon source and a nitrogen source to assemble nano-thin layers on a monodisperse silica sphere template and removes the silica template after high-temperature graphitization (Fig. 1). The prepared hollow carbon spheres have the advantages of controllable size (maximum 900 nm in diameter), thin wall (5-12 nm), mesoporous structure, nitrogen doping (nitrogen content 3.2%), and the like (FIG. 2). This achievement provides a new idea for the synthesis of nanostructured carbon materials and the study of functional group chemistry. At present, the two sides are conducting in-depth cooperation around new doping structure design, application performance research, feasibility exploration of large-scale production, and other aspects.
Related work was published in the Journal of Materials Chemistry A published in the first issue of 2013 (DOI: 10.1039/C2TA01013E).
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