The impregnation of mesoporous carbon cloth with alumina has been studied. The most successful method of impregnation resulted from preparation of the alumina phase by a sol/gel route. This method involves a boehmite intermediate, and the heating environment for the thermal transition of boehmite to the final alumina was investigated. Heat treatment of the boehmite intermediate under flowing N2, flowing air and vacuum was found to give a different pore size distribution for the final alumina than did still air heat treatment. For the former environments the transition from boehmite to alumina was not accompanied by the usual increase in pore size. Alumina/carbon composites were made by dipping pieces of mesoporous carbon cloth in a boehmite sol. The distribution of boehmite about the carbon cloth was found to be improved by pre-wetting the carbon cloth and by the use of ultrasonic dispersion during boehmite impregnation. Dried boehmite/carbon composites, with loading levels of up to 180wt.%, were heated under vacuum to 5000 C. In this manner alumina/carbon composites of up to 60wt.% alumina were fabricated. The distribution of the alumina phase about the carbon cloth was investigated by electron microscopy and by gas adsorption techniques. Nitrogen isotherm data indicated that the mesopores of the carbon cloth were not blocked by the deposited alumina, rather the pore volume of the carbon cloth was increased by the clustering of porous alumina about the pore entrances of the carbon cloth. Water isotherms were determined for the composite materials. The water activity of the composite, particularly at low relative pressures, was found to be significantly greater than that of the carbon cloth as a result of the presence of alumina. CO2 activity of the composites was investigated by a gas chromatographic technique. The CO2 activity of the composite material was found to be up to 500 times greater than that of virgin carbon cloth.

abstract: This dissertation provides a fundamental understanding of the properties of mesoporous carbon based materials and the utilization of those properties into different applications such as electrodes materials for super capacitors, adsorbents for water treatments and biosensors. The thickness of mesoporous carbon films on Si substrates are measured by Ellipsometry method and pore size distribution has been calculated by Kelvin equation based on toluene adsorption and desorption isotherms monitored by Ellipsometer. The addition of organometallics cobalt and vanalyl acetylacetonate in the synthesis precursor leads to the metal oxides in the carbon framework, which largely decreased the shrink of the framework during carbonization, resulting in an increase in the average pore size. In addition to the structural changes, the introduction of metal oxides into mesoporous carbon framework greatly enhances the electrochemical performance as a result of their pseudocapacitance. Also, after the addition of Co into the framework, the contraction of mesoporous powders decreased significantly and the capacitance increased prominently because of the solidification function of CoO nanoparticles. When carbon-cobalt composites are used as adsorbent, the adsorption capacity of dye pollutant in water is remarkably higher (90 mg/g) after adding Co than the mesoporous carbon powder (2 mg/g). Furthermore, the surface area and pore size of mesoporous composites can be greatly increased by addition of tetraethyl orthosilicate into the precursor with subsequent etching, which leads to a dramatic increase in the adsorption capacity from 90 mg/g up to 1151 mg/g. When used as electrode materials for amperometric biosensors, mesoporous carbons showed good sensitivity, selectivity and stability. And fluorine-free and low-cost poly (methacrylate)s have been developed as binders for screen printed biosensors. With using only 5wt% of poly (hydroxybutyl methacrylate), the glucose sensor maintained mechanical integrity and exhibited excellent sensitivity on detecting glucose level in whole rabbit blood. Furthermore, extremely high surface area mesoporous carbons have been synthesized by introducing inorganic Si precursor during self-assembly, which effectively determined norepinephrine at very low concentrations. / Dissertation/Thesis / Ph.D. Chemical Engineering 2012

Highly ordered mesoporous carbon-silica nanocomposites with interpenetrating carbon and silica networks were synthesized by the evaporation-induced tri-constituent co- assembly approach. The removal of silica by concentrated NaOH solution produced mesoporous carbons, which contained not only the primary large pores, but also the secondary mesopores in the carbon walls. The thus synthesized mesoporous carbon was further activated by using ZnCl2. The activated mesoporous carbon showed an improved surface area and pore volume. The synthesized mesoporous carbon was tested for diuron removal from water and the results showed that the carbon gave a fast diuron adsorption kinetics and a high diuron removal capacity, which was attributable to the primary mesopore channels being the highway for mass transfer, which led to short diffusion path length and easy accessibility of the interpenetrated secondary mesopores. The optimal adsorption capacity of the porous carbon was determined to be 390 mg/g, the highest values ever reported for diuron adsorption on carbon-based materials.

No description available.

The results of this study show that novel mesoporous carbons were obtained as inverse replica of SBA-15, HMS and MCM-41 silica templates, with a large pore diameter (2-4 nm), a BET surface area of 1867, 874 and 910 m2g –1 respectively for CA_SBA-15_LPG_105, CA_HMS_LPG_80 and CA_MCM- 41_LPG_80 with bimodal pore size distribution (PSD) in the mesopores range. The results obtained show that mesoporous carbon with graphitic structures can be synthesized via the LPG route.

The results of this study show that novel mesoporous carbons were obtained as inverse replica of SBA-15, HMS and MCM-41 silica templates, with a large pore diameter (2-4 nm), a BET surface area of 1867, 874 and 910 m2g –1 respectively for CA_SBA-15_LPG_105, CA_HMS_LPG_80 and CA_MCM- 41_LPG_80 with bimodal pore size distribution (PSD) in the mesopores range. The results obtained show that mesoporous carbon with graphitic structures can be synthesized via the LPG route.

Philosophiae Doctor - PhD / The results of this study show that novel mesoporous carbons were obtained as inverse replica of SBA-15, HMS and MCM-41 silica templates, with a large pore diameter (2-4 nm), a BET surface area of 1867, 874 and 910 m2g–1 respectively for CA_SBA-15_LPG_105, CA_HMS_LPG_80 and CA_MCM- 41_LPG_80 with bimodal pore size distribution (PSD) in the mesopores range. The results obtained show that mesoporous carbon with graphitic structures can be synthesized via the LPG route. / South Africa

The exploration of functional materials to store renewable, clean, and efficient energies for electric vehicles (EVs) has become one of the most popular topics in both material chemistry and electrochemistry. Rechargeable lithium batteries and fuel cells are considered as the most promising candidates, but they are both facing some challenges before the practical applications. For example, the low discharge capacity and energy density of the current lithium ion battery cannot provide EVs expected drive range to compete with internal combustion engined vehicles. As for fuel cells, the rapid and safe storage of H2 gas is one of the main obstacles hindering its application. In this thesis, novel mesoporous/nano functional materials that served as cathodes for lithium sulfur battery and lithium ion battery were studied. Ternary lithium transition metal nitrides were also synthesized and examined as potential on-board hydrogen storage materials for EVs. Highly ordered mesoporous carbon (BMC-1) was prepared via the evaporation-induced self-assembly strategy, using soluble phenolic resin and Tetraethoxysilane (TEOS) as precursors and triblock copolymer (ethylene oxide)106(propylene oxide)70(ethylene oxide)106 (F127) as the template. This carbon features a unique bimodal structure (2.0 nm and 5.6 nm), coupled with high specific area (2300 m2/g) and large pore volume (2.0 cm3/g). The BMC-1/S nanocomposites derived from this carbon with different sulfur content exhibit high reversible discharge capacities. For example, the initial capacity of the cathode with 50 wt% of sulfur was 995 mAh/g and remains at 550 mAh/g after 100 cycles at a high current density of 1670 mA/g (1C). The good performance of the BMC-1C/S cathodes is attributed to the bimodal structure of the carbon, and the large number of small mesopores that interconnect the isolated cylindrical pores (large pores). This unique structure facilitates the transfer of polysulfide anions and lithium ions through the large pores. Therefore, high capacity was obtained even at very high current rates. Small mesopores created during the preparation served as containers and confined polysulfide species at the cathode. The cycling stability was further improved by incorporating a small amount of porous silica additive in the cathodes. The main disadvantage of the BMC-1 framework is that it is difficult to incorporate more than 60 wt% sulfur in the BMC-1/S cathodes due to the micron-sized particles of the carbon. Two approaches were employed to solve this problem. First, the pore volume of the BMC-1 was enlarged by using pore expanders. Second, the particle size of BMC-1 was reduced by using a hard template of silica. Both of these two methods had significant influence on improving the performance of the carbon/sulfur cathodes, especially the latter. The obtained spherical BMC-1 nanoparticles (S-BMC) with uniform particle size of 300 nm exhibited one of the highest inner pore volumes for mesoporous carbon nanoparticles of 2.32 cm3/g and also one of the highest surface areas of 2445 m2/g with a bimodal pore size distribution of large and small mesopores of 6 nm and 3.1 nm. As much as 70 wt% sulfur was incorporated into the S-BMC/S nanocomposites. The corresponding electrodes showed a high initial discharge capacity up to 1200 mAh/g and 730 mAh/g after 100 cycles at a high current rate 1C (1675 mA/g). The stability of the cells could be further improved by either removal of the sulfur on the external surface of spherical particles or functionalization of the C/S composites via a simple TEOS induced SiOx coating process. In addition, the F-BMC/S cathodes prepared with mesoporous carbon nanofibers displayed similar performance as the S-BMC/S. These results indicate the importance of particle size control of mesoporous carbons on electrochemical properties of the Li-S cells. By employing the order mesoporous C/SiO2 framework, Li2CoSiO4/C nanocomposites were synthesized via a facile hydrothermal method. The morphology and particle size of the composites could be tailored by simply adjusting the concentrations of the base LiOH. By increasing the ratio of LiOH:SiO2:CoCl2 in the precursors, the particle size decreased at first and then went up. When the molar ratio is equal to 8:1:1, uniform spheres with a mean diameter of 300-400 nm were obtained, among which hollow and core shell structures were observed. The primary reaction mechanism was discussed, where the higher concentration of OH- favored the formation of Li2SiO3 but hindered the subsequent conversion to Li2CoSiO4. According to the elemental maps and TGA of the Li2CoSiO4/C, approximately 2 wt% of nanoscale carbon was distributed on/in the Li2CoSiO4, due to the collapse of the highly ordered porous structure of MCS. These carbons played a significant role in improving the electrochemical performance of the electrode. Without any ball-mill or carbon wiring treatments, the Li2CoSiO4/C-8 exhibited an initial discharge capacity of 162 mAh/g, much higher than that of the sample synthesized with fume silica under similar conditions and a subsequent hand-mixing of Ketjen black. Finally, lithium transition metal nitrides Li7VN4 and Li7MnN4 were prepared by high temperature solid-state reactions. These two compounds were attempted as candidates for hydrogen storage both by density functional theory (DFT) calculations and experiments. The results show that Li7VN4 did not absorb hydrogen under our experimental conditions, and Li7MnN4 was observed to absorb 7 hydrogen atoms through the formation of LiH, Mn4N, and ammonia gas. While these results for Li7VN4 and Li7MnN4 differ in detail, they are in overall qualitative agreement with our theoretical work, which strongly suggests that both compounds are unlikely to form quaternary hydrides.

Template synthesis and mesostructural characterization of ordered mesoporous silica, titania and carbon materials have been systematically investigated in this study. In order to obtain a better understanding of the template-precursor relationship, there are two templates adopted in this research. One is the ¡§liquid crystal template (LCT)¡¨, composed of surfactants via self-assembly pathway; the other is the ¡§ordered silica spheres template¡¨, composed of monodispersed SiO2 spheres (~40 nm) via gravity sedimentation. This work was carried out in four related directions: (1) Synthesis and functionalization of ordered mesoporous silicate (MCM-41 and MCM-48) via cationic surfactant template; (2) Using anionic surfactant template-assisted via urea treatment to control the morphology of the TiO2; (3) Synthesis of ordered mesoporous anatase TiO2 via cationic surfactant template; (4) Synthesis of ordered mesoporous carbon from mesophase pitch solution via silica spheres template. Mesoporous silica materials MCM-41 and MCM-48 have been synthesized and identified. The MCM-41 has a hexagonal phase (p6m) with surface area of 1006.90 m2/g and pore size of 37.65 Å, The MCM-48 has cubic phase ( ) with surface area of 1093.34 m2/g and pore size of 29.20 Å. The calcined MCM-41was rehydrated by heating in water and functionalized with 3-amino propyltrimethoxysilane; this functionalized mesoporous silica is targeted as a template of metal oxides, such as TiO2. appears the same tendency of parent MCM-41 in the N2 sorption isotherm measurements. Nanocrystalline TiO2 rods and hollow-tubes with an engraved pattern on the surface have been prepared by the anionic template-assisted sol-gel synthesis via urea treatment and under hydrothermal condition. X-ray diffractometry (XRD) results indicate that these nanocrystallines consist predominantly of anatase TiO2, with minor amounts of rutile and brookite. The crystallographic facetting found from SEM and TEM further reveals the polymorphic nature of the nanocrystalline TiO2 thus prepared. A ¡§reverse micelle¡¨ formation mechanism taking into account the hydrothermal temperature, the pH effect of the sol-gel system, the isoelectric point, the formation of micelles, and the electrostatic interaction between the anionic surfactant and the growing TiO2 particulates is proposed to illustrate the competition between the physical micelle assembly of the ionic surfactants and the chemical hydrolysis and condensation reactions of the Ti precursors. Ordered mesoporous TiO2 materials with an anatase framework have been synthesized by using a cationic surfactant template and soluble peroxytitanates as Ti precursor through an S+I− self-assembly pathway. The low-angle X-ray diffraction (XRD) pattern of the as-prepared mesoporous TiO2 materials indicates a hexagonal mesostructure. XRD and TEM results and N2 sorption isotherms measurements indicate the calcined mesoporous TiO2 possesses an anatase crystalline framework having a maximum pore size of 6.9 nm and a maximum BET specific surface area of 284 m2/g. This ordered mesoporous TiO2 also demonstrates a high photocatalytic activity for degradation of methylene blue under ultraviolet irradiation. Under a lower carbonization temperature and with a mesophase pitch solution as the carbon precursor, ordered mesoporous carbon thick films with 35-nm pore size have been synthesized using SiO2 spheres as the template. The pore size of the mesoporous carbon thus fabricated was the smallest one ever reported using silica templates. SEM and TEM patterns show a discernible morphology of an ordered cubic close-packing of the mesopores interconnected via holes of 6 nm in diameter. From this study, the template synthesis has been proven to be an effective method to fabricate mesoporous silica, polymorphic titania, ordered mesoporous TiO2, and ordered mesoporous carbon materials. Further utilization of this template synthesis is expected to offer a variety of porous networks with a wide range of pore sizes, well-defined morphologies on controllable length scales, and various chemical functionalities to match the needs of different applications.

The exploration of functional materials to store renewable, clean, and efficient energies for electric vehicles (EVs) has become one of the most popular topics in both material chemistry and electrochemistry. Rechargeable lithium batteries and fuel cells are considered as the most promising candidates, but they are both facing some challenges before the practical applications. For example, the low discharge capacity and energy density of the current lithium ion battery cannot provide EVs expected drive range to compete with internal combustion engined vehicles. As for fuel cells, the rapid and safe storage of H2 gas is one of the main obstacles hindering its application. In this thesis, novel mesoporous/nano functional materials that served as cathodes for lithium sulfur battery and lithium ion battery were studied. Ternary lithium transition metal nitrides were also synthesized and examined as potential on-board hydrogen storage materials for EVs. Highly ordered mesoporous carbon (BMC-1) was prepared via the evaporation-induced self-assembly strategy, using soluble phenolic resin and Tetraethoxysilane (TEOS) as precursors and triblock copolymer (ethylene oxide)106(propylene oxide)70(ethylene oxide)106 (F127) as the template. This carbon features a unique bimodal structure (2.0 nm and 5.6 nm), coupled with high specific area (2300 m2/g) and large pore volume (2.0 cm3/g). The BMC-1/S nanocomposites derived from this carbon with different sulfur content exhibit high reversible discharge capacities. For example, the initial capacity of the cathode with 50 wt% of sulfur was 995 mAh/g and remains at 550 mAh/g after 100 cycles at a high current density of 1670 mA/g (1C). The good performance of the BMC-1C/S cathodes is attributed to the bimodal structure of the carbon, and the large number of small mesopores that interconnect the isolated cylindrical pores (large pores). This unique structure facilitates the transfer of polysulfide anions and lithium ions through the large pores. Therefore, high capacity was obtained even at very high current rates. Small mesopores created during the preparation served as containers and confined polysulfide species at the cathode. The cycling stability was further improved by incorporating a small amount of porous silica additive in the cathodes. The main disadvantage of the BMC-1 framework is that it is difficult to incorporate more than 60 wt% sulfur in the BMC-1/S cathodes due to the micron-sized particles of the carbon. Two approaches were employed to solve this problem. First, the pore volume of the BMC-1 was enlarged by using pore expanders. Second, the particle size of BMC-1 was reduced by using a hard template of silica. Both of these two methods had significant influence on improving the performance of the carbon/sulfur cathodes, especially the latter. The obtained spherical BMC-1 nanoparticles (S-BMC) with uniform particle size of 300 nm exhibited one of the highest inner pore volumes for mesoporous carbon nanoparticles of 2.32 cm3/g and also one of the highest surface areas of 2445 m2/g with a bimodal pore size distribution of large and small mesopores of 6 nm and 3.1 nm. As much as 70 wt% sulfur was incorporated into the S-BMC/S nanocomposites. The corresponding electrodes showed a high initial discharge capacity up to 1200 mAh/g and 730 mAh/g after 100 cycles at a high current rate 1C (1675 mA/g). The stability of the cells could be further improved by either removal of the sulfur on the external surface of spherical particles or functionalization of the C/S composites via a simple TEOS induced SiOx coating process. In addition, the F-BMC/S cathodes prepared with mesoporous carbon nanofibers displayed similar performance as the S-BMC/S. These results indicate the importance of particle size control of mesoporous carbons on electrochemical properties of the Li-S cells. By employing the order mesoporous C/SiO2 framework, Li2CoSiO4/C nanocomposites were synthesized via a facile hydrothermal method. The morphology and particle size of the composites could be tailored by simply adjusting the concentrations of the base LiOH. By increasing the ratio of LiOH:SiO2:CoCl2 in the precursors, the particle size decreased at first and then went up. When the molar ratio is equal to 8:1:1, uniform spheres with a mean diameter of 300-400 nm were obtained, among which hollow and core shell structures were observed. The primary reaction mechanism was discussed, where the higher concentration of OH- favored the formation of Li2SiO3 but hindered the subsequent conversion to Li2CoSiO4. According to the elemental maps and TGA of the Li2CoSiO4/C, approximately 2 wt% of nanoscale carbon was distributed on/in the Li2CoSiO4, due to the collapse of the highly ordered porous structure of MCS. These carbons played a significant role in improving the electrochemical performance of the electrode. Without any ball-mill or carbon wiring treatments, the Li2CoSiO4/C-8 exhibited an initial discharge capacity of 162 mAh/g, much higher than that of the sample synthesized with fume silica under similar conditions and a subsequent hand-mixing of Ketjen black. Finally, lithium transition metal nitrides Li7VN4 and Li7MnN4 were prepared by high temperature solid-state reactions. These two compounds were attempted as candidates for hydrogen storage both by density functional theory (DFT) calculations and experiments. The results show that Li7VN4 did not absorb hydrogen under our experimental conditions, and Li7MnN4 was observed to absorb 7 hydrogen atoms through the formation of LiH, Mn4N, and ammonia gas. While these results for Li7VN4 and Li7MnN4 differ in detail, they are in overall qualitative agreement with our theoretical work, which strongly suggests that both compounds are unlikely to form quaternary hydrides.