Mesocellular Foam Carbons: Aggregates of Hollow Carbon Spheres with Open and Closed Wall Structures

A mesostructured hollow sphere form of carbon can be synthesized by using mesocellular foam (MCF) silica as template. A carbon structure composed of spherical hollows with closed walls and with mesopores of around 4 nm in diameter was prepared by the two-step impregnation of sucrose and successive carbonization under flowing argon at 900 C. A temperature-programmed oxidation experiment revealed that the mesoporous carbon released argon atoms when heated above 600 C, when oxidation of the carbon walls occurred. This result provides evidence for the presence of a large void volume inside the carbon spheres and implies that the pore size of 4 nm is due to the interspheric space. A single-step impregnation of sucrose resulted in the formation of open-walled mesospheres with pores of 4, 18, and 24 nm. The two larger pore sizes are attributed to the diameters of the window and of the cell as in MCF-silica. Platinum was loaded on these mesoporous carbons. The metal was highly dispersed (~0.4 nm by EXAFS) on the enclosed mesospheric carbon, while the material that grew in the pores of the open mesospheres consisted of particles that were around 15 nm diameter, as estimated by the Scherrer equation