Large-pore ordered mesoporous silicas and carbons: synthesis, characterization, and application

Abstract

Replication of mesoporous silica to ordered mesoporous carbon (OMC) has been studied with the large-pore MCM-48-like cubic Ia-3d mesoporous silica (KIT-6), with a particular interest in the effect of the silica pore connectivity. The carbonization was performed with sucrose or furfuryl alcohol under various conditions. The resultant OMC samples were characterized by powder X-ray diffraction, transmission electron microscopy, and nitrogen physisorption. The result indicates that the OMC pore structures and diameters can be systematically regulated by hydrothermal treatment of the silica template during synthesis, post-synthetic surface modification, variation of the silica source to surfactant ratio, and choice of catalysts for the polymerization of furfuryl alcohol. Thereby, the controllable range of OMC pore diameters has been increased to 13 nm from the 2 - 5 nm range obtained so far. Here, the most important factor is to control the pair-wise joining of enantiomeric carbon frameworks formed inside the silica template. Electrochemical performance of large-pore ordered mesoporous carbon (OMC) with a highly ordered mesoporous structure is investigated in two-electrode supercapacitors. Large-pore OMC with 8 - 13 nm in diameter has been prepared by templating technique using MCM-48-like cubic Ia-3d large mesoporous silica as a template and various carbon precursors; furfuryl alcohol, sucrose, and mesophase pitch. Potassium hydroxide activation provided additional microporous surface area of $2200 m^2/g$ to the OMC samples. The resultant OMC materials were characterized by powder X-ray diffraction, $N_2$ physisorption analysis, and four probes electronic conductivity measurement. The performance and electrochemical properties of the supercapacitors was investigated in acidic and organic electrolytic solutions by cyclic voltammetry, constant current discharge techniques, and ac impedance spectroscopy. The result indicates that the presence of ordered large mesopo...