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

Abstract

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 th...