Synthesis and Characterization of Hexagonally Ordered Carbon Nanopipes

Abstract

CMK-5 ordered mesoporous carbons that consist of two-dimensional (2-D) hexagonal arrays of pipes were synthesized using furfuryl alcohol as a carbon source and SBA-15 aluminosilicate of 2-D hexagonal structure as a template. External and internal pipe diameters were varied concomitantly by using SBA-15 templates with different pore diameters. The internal pipe diameter was also adjustable by changing conditions of the deposition of the carbon film on the walls of the template. It was shown that, under the typical synthesis conditions, furfuryl alcohol is fully polymerized inside SBA-15 pores. The internal pores of the pipes are generated during pyrolysis of the furfuryl alcohol under vacuum conditions. These pores are quite uniform in diameter, although there was evidence for the presence of constrictions in them, which may be related to the internal surface roughness or corrugation. The thickness of the carbon layer on the walls of the SBA-15 template was estimated as a difference between the pore radius of the template and the pore radius of the SBA-15/carbon composite, and it was found to be in the range 0.6−1.3 nm. This value is expected to correspond to the thickness of the walls of the carbon tubes, although the walls may be locally much thicker because of the occurrence of roughness or corrugation of the internal surface of the tubes. Despite the fact that the SBA-15/carbon composites exhibited moderate specific surface areas and pore volumes, the CMK-5 carbons obtained after the SBA-15 template removal exhibited very high nitrogen BET specific surface areas (about 2000 m 2 g - 1 ) and total pore volumes (about 1.5 cm 3 g - 1 ), which is likely to be related to a unique surface-templated structure of CMK-5 carbons. The internal volume of the mesoporous pipes tended to be smaller than the volume of mesopores between the pipes.