Synthesis of Discrete and Dispersible Hollow Carbon Nanospheres with High Uniformity by Using Confined Nanospace Pyrolysis

摘要

In recent years, hollow carbon nanospheres (HCSs) have attracted a great deal of attention because of their unique properties such as high surface-to-volume ratios, and excellent chemical and thermal stabilities. In this regard, HCSs are superior to polymer- and metal-based hollow nanospheres. HCSs are promising materials in a variety of applications such as adsorption, lithium ion batteries, fuel cells, and catalysis, and can also serve as building blocks for complex structures. The success of HCSs in these applications relies strongly on the availability of HCSs with carefully controlled diameter and shell thickness, surface properties, crystallinity of the carbon shell, and dispersibility in media. Much effort has been devoted to the synthesis of HCSs by a nanocasting approach. However, most previous reports on HCSs have the sole aim of obtaining hollow structural units, and little attention has been paid to addressing the issue of particle conglutination. In fact, an inevitable tendency of all carbon nanostructures during high-temperature annealing is the incidental condensing and sintering. Consequently, the end results are often nondispersible and conglutinated bulky materials. This challenge becomes even greater when the carbon particles are smaller, for example, below 200 nm. Discrete and dispersible HCSs are of critical importance for both the fundamental study of carbon colloids and for many practical applications such as colloidal catalysts, drug carriers, nanodevices, and inks. However, to the best of our knowledge, no feasible solution has been reported to date that can satisfactorily resolve the issue of conglutination for carbon nanoparticles. Thus, it remains a great challenge to develop a simple and effective strategy to overcome the barrier and to produce discrete and dispersible HCSs with high uniformity.