Fabrication Of CMK-5 Mesoporous Carbon By The Chemical Vapor Deposite And Its Catalytic Properties

The controllable synthesis of carbon materials with various morphology, structure and the graphitization degree (electronic conductivity) is one of the most interesting topics in the materials sciences. The establishement of the correlation between the structure and the functionalization of the porous carbon is crucial to their extensive applications.In this work, we described a novel chemical vapor deposition (CVD) method to synthesize Fe/SBA-15/carbon composites, using ferrocene as carbon precursor and SBA-15 as hard template. The highly ordered mesoporous CMK-5 carbon materials and/or the Fe2O3/SBA-15 composites could be facilely obtained by selectively removing the silica template (in dilute HF aqueous sloution) or combusting carbon and oxidizing the metal Fe into Fe2O3 in air. The electrochemical activities of Pt nanoparticles loaded on the CMK-5 carbon materials toward the methanol electrochemical oxidation were investigated by cyclic voltammograms. While the catalytic performances of Fe2O3/SBA-15 composites were studied in term of the Friedel-Crafts alkylation reaction.The ferrocene was found to be a new precursor to prepare CMK-5 nanopipes. The pipe thicknesses, pore volume as well as the specific surface area of the obtained CMK-5 can be facilely controlled by changing the CVD duration time from 20 to 120 min. It was found that the pore wall of the CMK-5 consisted of improved graphitic carbon due to the presence of the in-situ generated nanosized Fe during the CVD process. The pyrolysis of Fe/SBA-15/carbon composites above 850°C eventually resulted in the partial collapse of ordered CMK-5 nanopipes accompanied by the appearance of a considerable amount of entangled graphitic ribbons. The obtained CMK-5 was applied as a catalyst support for Pt loading. The particle size of Pt on the CMK-5 (~3.0 nm) is generally smaller than that loaded on the commercial XC-72 (~5.0 nm). The Pt/CMK-5 exhibied much higher current density than that on Pt/XC-72 under otherwise the indentical operation condition for methanol oxidation, which was ascribed to the high surface area as well as the high graphitization of CMk-5 carbon supports.The CVD method was proved to be an effective synthetic route to prepare the homogeneous distributed Fe2O3 nanocatalyst within the nanopores of SBA-15. The content of Fe2O3 in Fe2O3/SBA-15 composite can be adjusted by changing the CVD time. It was found that for Fe2O3/SBA-15-t prepared with extended t > 60 min, portions of the Fe2O3 tend to form aggregates on the external surfaces of the SBA-15, which was mainly ascribed to the oxidation process of the carbon. Moreover, the Fe2O3 particles dispersed in the mesopores and on the external surfaces of SBA-15 could undergo different reduction pathways. The Fe2O3/SBA-15 composite exhibited high selectivity, very high activities in term of benzylation reaction of benzene with benzyl chloride. The activities of composites were also found to be very sensitive to the reaction temperature. Both the dispersion of Fe2O3 and the mesopore of the composites could have a significant influence to the performances.