The local and surface structure of ordered mesoporous carbons from nitrogen sorption, NEXAFS and synchrotron radiation studies

Ordered mesoporous carbon materials were prepared by pyrolysis of sucrose and furfuryl alcohol templated in the ordered mesoporous silicate SBA-15. The structure of SBA-15 template was modified by changing the calcination temperature, we investigate the structural transformation of the silica template with calcination temperature using X-ray diffraction and nitrogen adsorption isotherms. SBA-15 calcined to 300 °C has a total pore volume of 1.13 cm3/g, a BET surface area of 1100 m2/g, and a pore spacing of 114 Å; when calcined to 90 °C the corresponding values are 0.40 cm3/g, 330 m2/g and 92.5 Å. Despite marked differences in SBA-15 template structure, the pore size distribution of the ordered mesoporous carbons is more dependent on the choice of precursor than on SBA-15 pore geometry. The BET surface areas of ordered mesoporous carbons made from aqueous sucrose solutions (850–1050 m2/g) are independent of template geometry; while surface area of materials made from furfuryl alcohol (530–1190 m2/g) are a reflection of template geometry. Near-edge X-ray fine-structure (NEXAFS) spectroscopy reveal that the template–carbon interaction during the pyrolysis of sucrose-based carbons exerts a strong influence on the surface structure of final product, and that such effects are largely absent in the furfuryl alcohol-based materials. The pair-distribution function (PDF) calculated from high-energy synchrotron scattering measurements corroborates the NEXAFS results, yet also show that the template effect on the bulk carbon is minimal. Template compression acting in conjunction with hydrothermally induced effects exerted on the carbon during pyrolysis drives the resulting carbon to a more graphitic state.