Synthesis And Application Of Ordered Mesoporous Carbons And Their Composites

Ordered mesoporous carbon (OMC) materials have attracted considerable attention for their regular mesopore arrangement, narrow pore size distribution, high specific surface area, chemical inertness and high conductivity, which may result in wide applications in the fields of adsorption, separation, catalysis, energy storage and so on.Hard template approach which was widely used to prepare OMCs has many shortages, such as a long and complicated multi-step synthetic procedure and the waste of the expensive surfactants. Therefore, in this thesis we focused on exploring the synthesis of OMCs via two simple and effective methods, and investigating the electrochemical performance of OMCs as electrode materials for supercapacitors. Besides these, two types of OMC composites (OMC/Ni and OMC/Polyaniline (PANI)) were successfully prepared, and their magnetism and supercapacitor performance were investigated, respectively. The morphologies and structures of these materials were characterized by XRD, FE-SEM, TEM, HRTEM and FT-IR measurements. The relationship among synthesis methods, structures of the derived materials and the application performances was founded, and the formation mechanism was elucidated. The main results are as follows.Two novel synthesis routes of OMCs were developed. Firstly, mesoporous carbons with highly ordered structures were successfully synthesized by the carbonization of sulfuric-acid-treated silica/triblock copolymer/sucrose composites and subsequent removal of silica. During the synthesis, triblock copolymer P123 and sucrose were employed as both template agents and carbon precursors in order to improve the carbon yield. When the mass ratio of sucrose to P123 was 1:4, crystallization temperature was 100℃and carbonization temperature was 850℃, highly ordered mesoporous carbon (C-S) with the mean pore size of 3 nm, BET specific surface area of 610 m²/g and pore volume of 0.66 cm³/g was synthesized. Thermogravimetric analysis revealed that C-S consisted of ca. 27 wt.% sucrose carbon and ca. 73 wt.% P123 carbon, and there was noticeable interaction between sucrose and P123. Secondly, the evaporation-induced self-assembly (EISA) technique was developed to synthesize a series of OMCs in alkali media by use of triblock copolymers F108, F127 or P123 as template agent and resorcin/formaldehyde resin (RFR) as carbon precursor. By optimizing the synthesis conditions, it was concluded that mesoporous carbons with highly ordered pores were prepared when the mass ratio of alkali, F108 and resorcin was in the range of 0.3～0.5:1.5～2.5:1. This route, avoiding the use of hard silica template, possesses the advantages of simplicity, effectivity and low cost, and will be a most promising approach for the large-scale synthesis of OMCs.The relationship between electrochemical performance of OMCs as electrode materials for electric double-layer capacitors and their pore characteristics was elucidated by using galvanostatic charge-discharge test, cyclic voltammetry and impedance spectroscopy. It was found that all of OMCs exhibited the ideal double-layer capacitance behaviors. The material C-P exhibited the lowest resistance and highest specific capacitance value of 179 F/g, which can be attributed to its high specific surface area of 720 m²/g and pore size distribution centered at 3.6 nm. In addition, the noteworthy is that the capacitance maintenance at high current load and high-frequency capacitive performance of OMCs were better than those of the general activated carbons, wherein larger mesopores and high mesopore fraction played important roles.OMC or its precursor (carbon/silica composite) was used as body material to prepare OMC/PANI composites via in-situ polymerization method. Compared with OMC/PANI composites prepared via physical mixing method, the researches on the materials' configurations, structures and supercapacitor performances were developed, and the influence of the content of PANI, interface combination and pore structure on capacitance behaviors was deduced. It is inferred that, regardless of the synthesis method, composites' capacitances consisted of double layer capacitance and redox capacitance. When the mass ratio of OMC to aniline was 30:70, the OMC/PANI composite prepared by in-situ polymerization method exhibited highest special capacitance of 895 F/g. When their mass ratio was increased to 50:50, the outstanding high rate capability was obtained.Finally, EISA was developed to synthesize OMC/Ni composite in alkali ethanol by using F127 as template agent and Ni(NO₃)₂·6H₂O as nickel source. It is deduced that the nickel particles in composite prepared by increasing the mass ratio of Ni(NO₃)₂·6H₂O and F127 from 0.25:2 to 0.6:2 were dispersed more uniformly and the pores of carbon were more ordered. When their mass ratio was 0.25:2, the composites exhibited the combined characteristics of ferromagnetism and paramagnetism.