Mesostructured Hollow Spheres of Graphitic N-Doped Carbon Nanocast from Spherical Mesoporous Silica

Mesostructured hollow spheres of graphitic N-doped carbon (CNx) materials may be nanocast from solid core mesoporous silica SBA-15 spheres via a chemical vapor deposition (CVD) route. The hollow spheres are generated when the SBA-15 silica/carbon composite obtained after CVD is subjected to silica etching in hydrofluoric (HF) acid. Hollow spheres are only obtained for CVD temperatures above 900 °C; here we present data on materials prepared at 1000 °C. The use of acetonitrile as carbon precursor results in N-doped (CNx) materials with nitrogen content of ca. 6.5 wt %. The CNx hollow spheres prepared at 1000 °C exhibit a high level of graphitization as evidenced by powder X-ray diffraction analysis and Raman spectrocopic studies. The CNx hollow spheres also exhibit good mesostructural ordering and have high surface area (779 m2/g) and pore volume (0.66 cm3/g). We propose a mechanism for the formation of the hollow spheres and clarify the importance of the CVD temperature in their formation.