Seul-Yi Lee

Determination of the optimal pore size for improved CO2 adsorption in activated carbon fibers.

Commercially available activated carbon fibers (ACFs) were modified further by a chemical activation method to obtain superior CO(2) adsorption capacity. The relationship between the pore structure of the modified ACF and the CO(2) adsorption behaviors was investigated. Chemical activation (with KOH at a fixed activation temperature of 900°C for 1h and various KOH/ACF weight ratios ranging from 1 to 4) of ACF increased the total pore volume and specific surface area to 1.124 cm(3)g(-1) (KOH/ACF weight ratio of 2) and 2318 m(2)g(-1) (KOH/ACF weight ratio of 4), respectively. Compared to ACF, the total pore volume and specific surface area were improved by factors of 2.5 and 2.3, respectively. Interestingly, the highest CO(2) adsorption capacity of 250 mg g(-1) at 298 K and 1 bar was observed at a KOH/ACF weight ratio of 3. The modified ACF had the narrowest microporosity ranging from 0.5 to 0.7 nm. Therefore, the increase in CO(2) adsorption capacity after chemical activation is closely related to the narrower pore size distribution rather than the total or micropore volume and specific surface area.

A study on hydrogen-storage behaviors of nickel-loaded mesoporous MCM-41.

The objective of the present work was to investigate the possibility of improving the hydrogen-storage capacity of mesoporous MCM-41 containing nickel (Ni) oxides (Ni/MCM-41). The MCM-41 and Ni/MCM-41 were prepared using a hydrothermal process as a function of Ni content (2, 5, and 10 wt.% in the MCM-41). The surface functional groups of the Ni/MCM-41 were identified by Fourier transform infrared spectroscopy (FTIR). The structure and morphology of the Ni/MCM-41 were characterized by X-ray diffraction (XRD) and field emission transmission electron microscopy (FE-TEM). XRD results showed a well-ordered hexagonal pore structure; FE-TEM also revealed, as a complementary technique, the structure and pore size. The textural properties of the Ni/MCM-41 were analyzed using N(2) adsorption isotherms at 77 K. The hydrogen-storage capacity of the Ni/MCM-41 was evaluated at 298 K/100 bar. It was found that the presence of Ni on mesoporous MCM-41 created hydrogen-favorable sites that enhanced the hydrogen-storage capacity by a spillover effect. Furthermore, it was concluded that the hydrogen-storage capacity was greatly influenced by the amount of nickel oxide, resulting in a chemical reaction between Ni/MCM-41 and hydrogen molecules.

Comprehensive review on synthesis and adsorption behaviors of graphene-based materials

Graphene is the thinnest known materials in the universe and the strongest ever measured. Graphene has emerged as an exotic material of the 21st century and received world-wide attention due to its exceptional charge transport, thermal, optical, mechanical, and adsorptive properties. Recently, graphene and its derivatives are considered promising candidates as adsorbent for H2 storage, CO2 capture, etc. and as the sensors for detecting individual gas molecule. The main purpose of this review is to comprehensive the synthesis method of graphene and to brief the adsorption behaviors of graphene and its derivatives.

Synthesis of zeolite-casted microporous carbons and their hydrogen storage capacity

Zeolite-casted microporous carbons (ZMiPCs) were synthesized using the replica casting method. The ZMiPC were also treated chemically by H(3)PO(4) (A-ZMiPC) or KOH (B-ZMiPC) impregnation, to investigate the effect of the acceptor-donor interaction on the hydrogen storage behaviors. The presence of functional groups of the modified ZMiPC surfaces was confirmed by X-ray photoelectron spectroscopy. The total acidity of the carbon surfaces was determined using the Boehm titration method. The microstructure was characterized by X-ray diffraction. The N(2)/77K adsorption/desorption isotherms were analyzed to characterize specific surface area, pore volume, and pore size distribution of the samples. The capacity of hydrogen adsorption was evaluated using a pressure-composition-temperature apparatus at 298 K/100 bar. From these results, the specific surface areas and micropore volume of ZMiPC increased more than two fold compared to the zeolite template. Meanwhile, the textural properties of A-ZMiPC and B-ZMiPC were decreased by the chemical treatments. Consequently, the largest hydrogen storage was obtained on A-ZMiPC, even though their textural properties had decreased, due to a charge induced dipole interaction between the modified carbon surface and hydrogen molecules.

Polymer matrices for carbon fiber-reinforced polymer composites

Carbon fibers (CFs) have high service temperature, strength, and stiffness, and low weight. They are widely used as reinforcing materials in advanced polymer composites. The role of the polymer matrix in the composites is to provide bulk to the composite laminate and transfer load between the fibers. The interface between the CF and the resin matrix plays a critical role in controlling the overall properties of the composites. This paper aims to review the synthesis, properties, and applications of polymer matrices, such as thermosetting and thermoplastic resins.

Influence of phosphoric acid treatment on hydrogen adsorption behaviors of activated carbons

The scope of this work investigates the relationship between the amount of oxygen-functional groups and hydrogen adsorption capacity with different concentrations of phosphoric acid. The amount of oxygen-functional groups of activated carbons (ACs) is characterized by X-ray photoelectron spectroscopy. The effects of chemical treatments on the pore structures of ACs are investigated by N2/77 K adsorption isotherms. The hydrogen adsorption capacity is measured by H2 isothermal adsorption at 298 K and 100 bar. In the results, the specific surface area and pore volume slightly decreased with the chemical treatments due to the pore collapsing behaviors, but the hydrogen storage capacity was increased by the oxygen-functional group characteristics of AC surfaces, resulting from enhanced electron acceptor-donor interaction at interfaces.

Hydrogen Storage Behaviors of Carbon Nanotubes/Metal-organic Frameworks-5 Hybrid Composites

In this work, the hydrogen storage behaviors of carbon nanotubes (CNTs)/metal-organic frameworks-5 (MOF-5) hybrid composites (CNTs/MOF-5) were studied. Hydrothermal synthesis of MOF-5 was conducted by conventional convection heating using 1-methyl-2-pyrrolidone (NMP) as a solvent. Morphological characteristics and average size of the CNTs/MOF- 5 were also obtained using a scanning electron microscopy (SEM). The pore structure and specific surface area of the CNTs/ MOF-5 were analyzed by N2/77 K adsorption isotherms. The capacity of hydrogen storage of the CNTs/MOF-5 was investigated at 298 K/100 bar. As a result, the CNTs/MOF-5 had crystalline structures which were formed by hybrid synthesis process. It was noted that the CNTs/MOF-5 can be potentially encouraging materials for hydrogen adsorption and storage applications at room temperature. Keywords : Carbon nanotubes, Metal-organic frameworks, Hydrogen storage, XRD, SEM

Effect of surface modification of mesoporous carbon supports on the electrochemical activity of fuel cells

Mesoporous carbon (MC) was prepared from mesoporous silica (SBA-15) via a conventional templating method for use as a Pt-Ru catalyst support in fuel cells. The effect of surface modifications of the carbon support at different pH on the electrochemical activities of the Pt-Ru/MC catalysts was investigated. The Pt-Ru nanoparticle size and loading were dependent on the surface characteristics of the MC. Base-modified MC-supported Pt-Ru showed the smallest average nanoparticle size (3.3 nm) and the highest loading (77%) among the chemically modified MC-supported Pt-Ru catalysts. The electrochemical activity of the catalysts was enhanced when the MC supports were treated with basic or neutral agents rather than by acid modification.

Effect of microporosity on nitrogen-doped microporous carbons for electrode of supercapacitor

Nitrogen-doped microporous carbons were prepared using a polyvinylidene fluoride/melamine mixture. The electrochemical performance of the nitrogen-doped microporous carbons after being subjected to different carbonization conditions was investigated. The nitrogen to carbon ratio and specific surface area decreased with an increase in the carbonization temperature. However, the maximum specific capacitance of 208 F/g was obtained at a carbonization temperature of 800°C because it produced the highest microporosity.

A novel drying process for oil adsorption of expanded graphite

Expanded graphite (EG) was prepared using a drying process for application as an oiladsorbent: the morphology, expansion volume, and oil absorption capacity of the EG were investigated. The expanded volume of the EG increased with an increasing reaction time and heat treatment temperature. The oil adsorption capacity of the EG was 45 g of n-dodecane per 1 g of EG. It is noted that the drying process of EG is a useful technique for a new oiladsorbent.