Papers by Keyword: Mesoporous Carbon

Abstract: In nature, kaolin clay is referred to a readily available cheap source of silicon and used in various fields such as the paper, ceramic, paint, plastic, rubber, and cracking catalyst industries. This paper introduces utilization of natural kaolin clay for a new application. In particular, the kaolin clay is used as a new raw material for synthesis of ordered mesoporous carbon (OMC) materials, which serve as electrode active materials for supercapacitors. Kaoline used in the present work is originated from Yen Bai province (Vietnam). After subjected several steps of the treatment process, silica present in the kaolin clay is converted to sodium silicate and used directly as a source of silicon for the synthesis process of mesoporous porous silica (SBA-15). The synthesized SBA-15 mesoporous silicas exhibit rod-like nanostructure with the specific area of 432.7 m2 g^-1 and the mean pore size of 7-8 nm. Subsequently, SBA-15 silica serves as hard template for preparation of OMCs by using nanocasting method. The OMCs carbonized at different temperatures in the absence and presence of boric acid reveal highly ordered mesoporous structure with the highest specific area of 1039.2 m2 g^-1 and the mean pore size ranging from 6 to 7 nm. As used as electrode active material in 6 M KOH aqueous solution, the resultant OMCs exhibit excellent capacitive performance with a specific capacitance higher than 80 F g^-1 at a scan rate of 5 mV s^-1. The obtained results show that, in addition to the high specific area, the electrical conductivity also plays an important role in enhancing energy storage ability of the OMC electrodes. At the same carbonization temperature, the high surface area plays crucial role. However, at the higher carbonization temperatures, effect of the electrical conductivity of the materials prevails over the high surface area. This study illustrates highly application feasibility of Vietnam natural kaolin clay as available and cheap raw material source for synthesis of electrode active materials with the high supercapacitive performance for electrochemical double layer capacitors.

Abstract: Effect of glucose loading on the synthesis mesoporous carbon had been studied using hard template method where mesoporous silica SBA-15 was used as a template. To obtain a large pore of mesoporous carbon sample, a large pore of silica template was used. A series of mesoporous carbon sample was synthesized by loading different amounts of glucose (2.5g, 5.0g and 10.0g) as a carbon precursor to ensure that the template was fully impregnated with precursor. After treatment process, the surface area of carbon samples were measured with Brunauer-Emmett-Teller (BET) analysis and it shows that higher amount of glucose gives higher surface area due to the large pore of the template used. The samples then were tested with cyclic voltammetry technique at different scan rates (10, 20, 30 and 50 mVs^-1) in 6M KOH electrolyte. It reveals that higher surface area samples show a higher specific capacitance with 119 F/g at slow scan rate 10 mVs^-1.

Abstract: A series of mesoporous carbon sample had been synthesized by using a modification of template silica, SBA-15. Sucrose was added into a large pore size of SBA-15 by using incipient wetness impregnation method. A proper carbonization and removal silica process had been done to produce large pore size of mesoporous carbon. Two electrode cells were prepared by coating mesoporous carbon into stainless steel mesh as a supercapacitor electrode. A few of electrolyte concentration also had been investigated by cyclic voltammetry using a various concentration of KOH in the range 1-12 M. It shows that 6M KOH gives a better performance of EDLC.

Abstract: A graphitic mesoporous carbon-based material (GMC) was prepared using a nano-casting process by using SBA-15 as a hard template and sucrose as a carbon precursor. Modification of GMC was carried out by chemical oxidation with nitric acid in order to generate surface functionalities. The oxidized GMC material was then used as adsorbent for Basic Red 2 (BR2) in aqueous solutions. The morphology, pore structure, and surface functional groups of GMC samples were evaluated by field emission scanning electron microscopy (FESEM), Brunauer-Emmett-Teller method (BET), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and Boehm titration. N2 adsorption-desorption analysis revealed a type IV isotherm characteristic of mesoporous materials with BET surface area approximately 1000 m2g-1 and pore volume 0.9 cm3g-1. The effects of different adsorption parameters such as initial pH, initial dye aqueous solution concentration and temperature on BR2 removal were investigated. After modification, the BET surface area slightly decreased but the adsorption capacity of BR2 increased with optimum adsorption in 200 ppm initial concentration, pH of 10 at 60 °C.

Abstract: Ordered mesoporous carbons are synthesized by using the triblock copolymer F127 (EO₁₀₆-PO₇₀-EO₁₀₆) and diblock copolymer PDMS-PEO (DMS₃₂-EO₂₀) as co-templates. KOH is utilized to improve the surface area and tailor the pore texture of the ordered mesoporous carbon. KOH activation significantly increases the surface area of mesoporous carbon due to the generation of micropores in mesopore walls. The obtained activated mesoporous carbons have high surface area (1592 m² g^-1) and large pore volume (0.79 cm³ g^-1). The activated carbons also exhibit improved electrochemical behavior with a specific capacitance of 218.9 F g^-1 at the current density of 1 A g^-1, excellent rate performance and good cycling stability, revealing a promising application in supercapacitors.

Abstract: Two kinds of mesoporous carbons (MPC) with three-dimensional (3D) body-centered cubic (Imm) and 2D hexagonal symmetry (p6m) were synthesized by using triblock copolymer PEO-PPO-PEO (F127) and diblock copolymer polydimethylsiloxane-poly (ethylene oxide) (PDMS-PEO) as co-templates and were further activated by nitric acid oxidation. The electrochemical performances of MPCs and acid-modified MPCs (H-MPCs) electrodes were investigated. After nitric acid modification, the capacitive performances of MPCs were obviously improved. The acid-modified sample with 2D p6m symmetry (H-2D-MPC) exhibited the highest specific capacitance of 237.1 F g^-1 in 6 M KOH at the current density of 1 A g^-1 and could be a potential candidate for supercapacitors.

Abstract: The composite electrode, formed by SnO₂-Sb as catalyst agent, mesoporous carbon (MC) and polytetrafluoroethylene (PTFE), was prepared and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and N₂ adsorption-desorption analyses. It has a high BET surface area of 184 m² g^-1 with a narrow pore distribution centered at 6.2 nm. The phenol removal of 96.3 % was achieved with the composite electrode in the electrochemical oxidation of aqueous phenol wastes after 80 min electrolysis while it was only 84.1 % for the SnO₂-Sb electrode. The removal of chemical oxygen demand (COD) was 62.9 % on the composite electrode which was also higher than that on the SnO₂-Sb electrode (38.3 %).

Abstract: A series of titanium doped ordered mesoporous carbons (Ti-OMCs) were prepared by employing titanium modified resol as source for the first time. The effect of titanium content and F127 content on the microstructure of Ti-OMCs was investigated by X-ray diffraction (XRD), N₂ sorption isothermal and Transmission electron microscopy (TEM). The results showed that regularity of products decreased with the increase of titanium content. A mesophase transformation from 2-D hexagonal (P6mm) to body-centered cubic () structure can be achieved by decreasing F127 content.

Abstract: Mesoporous carbons were prepared by one step method using hard coal pitch as carbon source, in which magnesium oxide was adopted as template. The adsorption value of vitamin B₁₂, specific surface and pore size distribution, surface topography of mesoporous carbons were tested by spectrophotometer, specific surface analyzer and scanning electron microscopy. The results showed that the vitamin B₁₂ absorption value on mesoporous carbon could be improved with suitable carbonization temperature and mass ratio of template agent to carbon source. The maximum value achieved to 103.82mg/g when the mass ratio of MgO to modified pitch was 8:2.

Abstract: Nitrogen hybrid ordered mesoporous carbons (N-OMC) were prepared by the soft-template method with melamine-phenol-formaldehyde resoles (MPF) as the precursors and triblock copolymer F127 as a soft-template. FT-IR spectra analysis demonstrated that nitrogen was incorporated into the mesoporous carbons with C-N covalent bonds. The effect of molar ratio of phenol to melamine on the pore structure and textural properties was discussed by small angle X-ray scattering, nitrogen adsorption measurements, and transmission electron microscopy. The results show that the degree of pore order decreases with the increasing of nitrogen content. The N-OMC with 3.39 wt% nitrogen has the highest specific surface areas (573m2/g) and best ordered mesostructure.