Nano structure of MgO-templated carbon and its change induced by heat-treatment

Abstract

The nanostructure of MgO-templated carbon synthesized through the decomposition of magnesium citrate was examined, and its structural change induced by heat-treatment was traced using various analysis techniques. A high resolution TEM analysis revealed that the carbon consisted of hollow nanoparticles with a size of 10 nm where the thickness of the carbon walls (shells) is several nanometers. N 2 adsorption analysis indicated that the MgO-templated carbon before the heat-treatment was highly mesoporous and microporous with a BET specific surface area as large as 1600 m 2 /g. Such a porous structure was almost unchanged even for the carbon heat-treated at 2000 °C, although surface areas of activated carbons were usually decreased in the lower temperature ranges. Above 2000 °C, the carbon nanostructure observed by TEM changed so that it was similar to heat-treated glassy carbon which is normally non-graphitizable. The templated-carbon, however, was graphitized by multiphase graphitization process with three different (0 0 4) diffraction peaks of carbon. The reason why such inconsistency occurred was not clear, but could be because of the difference in the surface area which is negligible for glassy carbons but not for the MgO-templated carbon. [TANSO 2012 (No. 254) 153–9.]