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Coal extract produced by solvent extraction of low-rank coal is not suitable for spinning due to its high oxygen content. In order to effectively overcome this limitation, soft pitch was produced by co-carbonization of coal extract and petroleum residues. The decrease in oxygen content was confirmed by physical property analyses of the soft pitches blended at different mixing ratios. A bridge/hydroaromatic structure of the soft pitch was observed during the co-carbonization. The produced spinnable pitch had a high spinnability and a softening point of 230 °C. This spinnable pitch, prepared by solvent extraction of low-rank coal, showed excellent spinnability and was heat-treated at 800 °C for 5 min to produce isotropic carbon fibers having diameters of 7 μm and a tensile strength of 1189 MPa. Thus, the co-carbonization of coal extract and petroleum residue is an effective method for the production of inexpensive spinnable pitch for isotropic carbon-fiber manufacture.

High-density carbon blocks are much lighter than metals and have excellent mechanical properties and are one of the materials garnering attention to replace existing metal parts. In this study, a binderless coke was produced by changing the flow rates of nitrogen and air as a carrier gas during heat treatment of coal tar pitch and using this, a green body was formed at 150 MPa and carbonized to produce a high-density carbon block. We express the binderless coke produced in this way by N10A0, N7A3, N5A5, N3A7, N0A10 according to the ratio of nitrogen and air, and in the case of carbon block, we have added CB in front of it. We then considered the effect of oxygen content in the binderless cokes on the optical, chemical, and mechanical properties. It was observed that the produced binderless cokes develop into a dense mosaic structure with a small particle size as the air flow rate increased. To survey the change in oxygen content of the produced binderless coke, O1s and C1s regions were measured using X-ray photoelectric spectroscopy (XPS), and O1s/C1s was calculated. The O1s/C1s ratio steadily increased as the air flow rate increased, and in the case of N0A10, it increased about twice as much as that of N10A0 to 11.20%. β-resin has a very large effect on the mechanical strength of the carbon block in addition to air in the pitch. And in the case of CB-N0A10, it shows the best mechanical strength with a density of 1.72 g/cm3, bending strength of 87 MPa, and shore hardness of 93 HSD.

In this study, surface oxidation of petroleum pitch was performed to enhance the thermal stability, specific surface area, and mesopore ratio of activated carbon. The oxygen uptake of the pitch by surface oxidation has a strong influence on the formation of the specific surface area and pore size of activated carbon. It was confirmed that the oxygen uptake from the surface to the inner side of the surface oxidized pitch was the highest at the temperature of 330 °C (IP330-AC), with a mesopore ratio of 63.35% and specific surface area of 1811 m2 g−1. The oxygen content of the surface oxidized pitch increased proportionately with the mesopore ratio in activated carbon. The specific surface area and mesopore ratio of IP330-AC were respectively 163% and 487% higher than those of petroleum-based commercial activated carbon (A-BAC), and 102% and 491% higher than those of coconut-based commercial activated carbon (P60).

We report on hierarchical porous carbons derived from rice husk (RH) through the combination of carbonization and two post-processing methods that were used as the electrode material for capacitive deionization (CDI). The carbonized RHs, consisting of carbon/inorganic composite materials, were used to control the hierarchical porous structures, depending on the existence of silicon domains. Hierarchical porous carbons, denoted as RHC-A and comprising dominant micropores and small fraction mesopores, were synthesized by steam activation to react with the carbon fraction in the presence of silicon components. On the other hand, mesopore-dominant porous carbons, denoted as RHC-H, were obtained selectively by removing silicon components acting as a natural template from carbonized RH by hydrofluoric acid treatment. In order to understand the effect of the pore structure on CDI performance, two RH-derived porous carbons were compared in terms of their performances in water purification. In the batch-mode experiment, the microporous activated carbon (AC) exhibited the highest maximum electrosorption capacity of 17.7 mg g−1, which was mainly determined by the specific surface area. Under the same conditions, however, the RHC-A was verified to have enhanced kinetic performance according to the Langmuir isotherm and the pseudo-second-order kinetic model. Here, the hierarchical porous structures with continuous mesopores interconnected by micropores contributed to the enhanced kinetic performance of the RHC-A, facilitating effective ion transport and adsorption. In a continuous mode similar to the practical CDI, the kinetically improved RHC-A achieved a higher salt-removal capacity of 8.09 mg g−1 than the 5.40 mg g−1 and 1.63 mg g−1 of the commercial activated carbon and RHC-H, respectively, at 1.5 V and with a feed rate of 20 mL min−1 in 100 ppm of NaCl solution.

The impurities in methanol fuel, which is used for direct methanol fuel cells (DMFCs), greatly affect the performance of membrane electrode assemblies (MEAs). The effect of ethanol in methanol fuel on the MEA performance was evaluated using the five different kinds of methanol fuels for reagent grade and industrial use. The impurities in the different kinds of methanol fuels that affected the performance of the MEAs were mainly ethanol evident by the analysis of the methanol fuels. Thus, this study suggests that the ethanol concentration in methanol fuels should be limited to achieve a higher performance of the MEAs.

This study increased the surface area of a membrane by forming patterns on the Nafion resin membrane using a stainless steel mesh to enhance the performance of a direct methanol fuel cell (DMFC) because the triple-phase boundary is extended. Nafion resin (F-form ( SO3F)) was used which has melt-moldability to form a stable surface pattern and to directly coat the catalyst layer by the bar-coating method. The performance (polarization and power density curves) and the resistance of the membrane-electrode assembly (MEA) were analyzed with a single cell and an impedance analyzer. The surface area of the patterned membranes was increased 1.99, 2.10, and 2.12 times compared to the flat membrane, and the power density also increased 12.9, 18.6, and 24.2% at 0.4 V, respectively. The performance of the MEA with the patterned membrane had a lower concentration polarization than that of the MEA with the flat membrane. The performance of the MEAs with the patterned membranes had a greater impact on the cathode side of the membrane than on the anode side. The results of these experiments offer a solution to the problem of a low performance of MEA, which is one of the disadvantages of DMFCs.

Tubular type carbon nanofibers (TCNFs) are prepared and used as a catalyst support material for a cathode electrode of low temperature fuel cells through structural modification. The pristine TCNF is treated by graphitization and makes partially torn-tube shape through the surface expansion by rapid thermal treatment of the oxidized graphitized TCNF. Physical properties of the TCNF group are examined, and it is confirmed that the unique ripped texture along fiber axis with graphitic structure is obtained by the surface expansion. Platinum catalysts supported on these TCNF group are prepared and evaluated. Electrochemical properties are examined via cyclic voltammograms and polarization curves for oxygen reduction reaction activity. The platinum catalyst on the surface expanded TCNF has the enhanced activity at initial and the stable performance even after accelerated durability test due to their unique structure.

High-strength and high-density carbonized carbon blocks from self-sintering coke were manufactured using coal tar and two-stage heat treatments (1st and 2nd stage treatments). First, the molecular weight distribution of the refined coal tar was controlled through a pressured heat treatment (1st stage treatment). Second, the 1st stage heat-treated coal tar (1S-CT) was treated using a delayed coking system (2nd stage treatment) to become the self-sintering coke. Finally, carbon blocks were molded from 2nd stage heat-treated coke (2S-C) and carbonized at 1200 °C for 1 h. Through rapid decomposition of the high molecular weight components in the coal tar at 360 °C in the 1st stage treatment, the molecular weight distribution of coal tar was confirmed to be controllable by the 1st stage treatment. Swelling during carbonization was observed in carbon blocks manufactured from 2S-C containing more than 15 wt% of volatile matter from 150–450 °C. The optimum conditions of the two-stage heat treatments were confirmed to be 300 °C for 3 h and 500 °C for 1 h. The highest density and flexural strength of the carbonized carbon blocks manufactured from 2S-C were 1.46 g/cm3 and 69.2 MPa, respectively.

In the present study, surface texture features and chemical properties of two types of cokes, made from coal tar by either 1-stage heat treatment or 2-stage heat treatment, were researched. The relationship between surface texture characteristics and the chemical properties was identified through molecular weight distribution, insolubility of coal tar, weight loss with temperature increase, coking yield, and polarized light microscope analysis. Rapidly cleared anisotropy texture in cokes was observed in accordance with the coking temperature rise. Quinoline insolubility and toluene insolubility of coal tar increased with a corresponding increases in coking temperature. In particular, the cokes produced by the 2-stage heat treatment (2S-C) showed surface structure of needle cokes at a temperature approximately 50°C lower than the 1-stage heat treatment (1S-C). Additionally, the coking yield of 2S-C increased by approximately 14% in comparison with 1S-C.

A membrane-assisted capacitive deionization (CDI) system was developed for the purification of water containing sodium chloride using activated carbon fibers (ACFs) as capacitor electrode materials. The ACFs have different degrees of activation with different surface areas and pore size distributions. Their desalination performance for sodium or chloride ions was investigated. Results indicate that the salt removal efficiency and surface area-normalized electrosorption capacity for each ion depend on the surface area, pore depth and the match between the pore sizes of the ACFs and the radius of each hydrated ion. A high surface area and shallow pores favor the salt removal efficiency and a high surface area-normalized electrosorption capacity. The ACF with a median pore size of 0.69 nm performs best for sodium ion removal and those with median pore sizes of 1.09 and 1.52 nm are best for chloride ion removal, which could be ascribed to the fact that the radius of a hydrated sodium ion (0.66 nm) is smaller than that of a hydrated chloride ion (0.72 nm). An asymmetric electrode material configuration is needed to optimize both the anion and cation adsorption in the membrane-assisted CDI system.

Nitrogen-doped carbon nanofibers (N-CNFs) with different nitrogen contents were synthesized from vaporized acetonitrile as a simultaneous carbon and nitrogen source via the chemical vapor deposition method. N-CNF synthesis was conducted at 640 °C for 2 h, and the ratio of nitrogen and hydrogen mixture as reactant gas was adjusted to control the nitrogen content in the N-CNFs. The amount of hydrogen in the reactant gas was varied in the range from 0 to 40 mL min − 1 . The physical and electrochemical properties of the N-CNFs were characterized. The content of introduced nitrogen decreased with the ratio of supplied hydrogen, as opposed to the growth yield of the N-CNFs. Additionally, the nitrogen content and chemical states of the N-CNFs were examined and compared to reveal their correlations with the electrochemical behavior. The N-CNFs were found to have a noticeable electrochemical behavior such as capacitance and oxygen reduction reaction activity that was determined by the total nitrogen contents, especially those of pyridinic-nitrogen.

Fuel cells have received worldwide attention as a next-generation renewable energy technology. However, catalyst cost and durability are the main issue hampering the commercialization of fuel cells. Many studies have focused on the physicochemical properties of the carbon support to improve the catalyst’s properties. Mesoporous carbons are suitable candidates because of their appropriate structural characteristics, including high surface area, large pore size, and regularly interconnected mesopores that permit efficient diffusion of the reactants and by-products. In this study, supports made from chestnut-like carbon consisting of platelet carbon nanofibers were fabricated by selective catalytic gasification of activated carbon. Pt/C catalysts were synthesized from these support structures using the impregnation method. Catalyst performance and characteristics were investigated by N2 adsorption/desorption isotherms, X-ray diffractions, and the rotating disk electrode technique for the oxygen reduction reaction.

The crystalline and microstructural transformations of two laboratory ashes and their quenched slags (from a gasifier) with similar chemical compositions [one with high silicon dioxide (SiO2) concentrations and the other with high aluminum oxide (Al2O3) concentrations] were systematically characterized using X-ray diffraction, multinuclear solid-state nuclear magnetic resonance, and a high-temperature viscometer. The results show that the content of SiO2 and Al2O3 in ash has significant influence on the crystal types and size of cristobalite clusters in the liquid slag during heat treatment. Consequently, the formed cristobalite clusters were crucial to the viscosities and rheological properties of liquid slags.

The effect of membrane thickness on the performance degradation of DMFCs was investigated during freeze-thaw cycling across temperatures ranging from −32 °C to 60 °C. Three cells with Nafion membranes of varying thickness were prepared: Nafion 112, Nafion 115 and Nafion 117. Performance degradation was evaluated by comparing the changes to electrode polarization, electrochemical impedance and cyclic voltammetry over a range of freeze-thaw cycles. It was determined that freeze-thaw cycling affected the performance of the three membrane electrode assemblies (MEA). A cell with a Nafion 112 membrane showed a more significant increase in cathode overpotential than cells with either a Nafion 115 or Nafion 117 membrane. The charge transfer resistance of the cell with a thin membrane was more affected by freeze-thaw cycles than the cells with thicker membranes. All three cells showed a significant decrease in ECSA after freeze-thaw cycles. Freeze-thaw cycles damaged the triple phase boundary region and decreased the ECSA of cells with thinner membranes, which cause rapid performance degradation. The use of thick membranes in MEAs was determined to be the effective method for reducing performance degradation during freeze-thaw cycling.

Tungsten carbides (WC) nanoparticles on platelet type-carbon nanofibers (p-CNFs) catalysts have been synthesized for alkaline direct ethanol fuel cells (ADEFC). Physical properties of WC/CNFs samples with various WC contents are analyzed by transmission electron microscope (TEM), thermal gravimetric analysis (TGA) and nitrogen isotherm (BET). The WC/CNFs catalysts showed an improved kinetics for the ethanol oxidation than p-CNFs did. It indicates that the significant increase in the catalytic activity for ethanol oxidation on WC/CNFs than p-CNFs did due to the synergistic structural effect between WC nanoparticles and the p-CNFs supports. WC/CNFs also showed good performances in ADEFC single cells. The maximum current density of P4W3 and P4W4 was 9.0 and 4.4 mA cm −2 , respectively. These catalysts can be used as the ethanol oxidation in direct ethanol fuel cells in alkaline media.

Proton exchange membranes were prepared by γ-ray radiation-induced grafting onto ETFE films, crosslinking with styrene/divinylbenzene (DVB) mixtures and a subsequent sulfonation. Effects of the DVB content on the membrane properties such as ion exchange capacity (IEC), proton conductivity, and methanol permeability were investigated. Membrane-electrode assemblies (MEA) containing the prepared membranes were fabricated for direct methanol fuel cells (DMFC), and the MEA performance was examined in operation with various concentrations of methanol. Durability of the MEAs was investigated using a 3 M methanol solution for 1000 h, and the polarization curves and impedance spectra were measured. Physicochemical properties of catalysts and membrane before and after the long-term operation were analyzed by TEM, XRD, IEC, and proton conductivity. Performance and durability of the selected membranes were also confirmed in the operation of a 6-cell stack with 3 M methanol solution.

This paper reports the effect of adding reduced graphene oxide (RGO) as a conductive material to the composition of an electrode for capacitive deionization (CDI), a process to remove salt from water using ionic adsorption and desorption driven by external applied voltage. RGO can be synthesized in an inexpensive way by the reduction and exfoliation of GO, and removing the oxygen-containing groups and recovering a conjugated structure. GO powder can be obtained from the modification of Hummers method and reduced into RGO using a thermal method. The physical and electrochemical characteristics of RGO material were evaluated and its desalination performance was tested with a CDI unit cell with a potentiostat and conductivity meter, by varying the applied voltage and feed rate of the salt solution. The performance of RGO was compared to graphite as a conductive material in a CDI electrode. The result showed RGO can increase the capacitance, reduce the equivalent series resistance, and improve the electrosorption capacity of CDI electrode.

The catalytic conversion of alkali metal carbonate (K2CO3) catalyst supported on perovskite oxide was carefully examined as an effective catalyst for low-temperature catalytic gasification of lignite. It showed much higher activity than K2CO3 alone as well as K2CO3 supported on γ-alumina under gasification conditions below 800 °C. Furthermore, catalyzed syngas had higher H2 and lower CO2 ratios than non-catalyzed syngas. Promisingly, there was also much less tar formation, less than 50 wt.% compared to non-catalyzed gasification. Also, less loss of K2CO3 and no coke formation on the catalyst surface were confirmed, comparing to the catalytic gasification with K2CO3 supported on γ-alumina.

Catalytic recovery after repeated uses of unsupported K2CO3 or K2CO3 supported on 3 kinds of perovskites (LaMn0.8Cu0.2O3, LaMn0.8Cu0.2O3/γ-alumina, and La0.9K0.1MnO3) was investigated during steam gasification of an Indonesian lignite (Adaro) at 700 °C. Perovskite supports effectively retained K2CO3 and maintained higher catalytic activity than K2CO3 alone. The supported catalysts were recovered from the ash after gasification based on their size and ferromagnetism. Quartz and alumina accumulation on the catalyst poisoned the ash due to reactivity with potassium. Catalytic activity as high as 90% carbon conversion was maintained up to seven cycles, and separation from the ash after gasification regenerated the activity.

Alumina-supported K2CO3–LaMn0.8Cu0.2O3 was investigated for the catalytic conversion of tar, produced from lignite, into syngas under inert and steam-reforming conditions. A double-bubble fluidized bed reactor system, equipped with a micro gas chromatograph and a collecting system to analyze permanent gases and condensable species, was developed to screen the catalytic conversion of tar components below 700 °C. The redox properties of catalysts, estimated by hydrogen temperature programmed reduction analyses, were correlated with their catalytic performance in tar conversion. The synthesized catalyst effectively converted tars into hydrogen-rich syngas and also improved tar reforming by inhibiting coke deposition.

In this study, we develop a one-dimensional (1-D), two-phase, transient-thermal DMFC model to investigate the effect of methanol concentration fluctuation that usually occurs in active-type direct methanol fuel cell (DMFC) systems. 1-D transient simulations are conducted and time-dependent behaviors of DMFCs are analyzed under various DMFC operating conditions such as anode/cathode stoichiometry, cell temperature, and cathode inlet humidification. The simulation results indicate that the effect of methanol concentration fluctuation on DMFC performance can be mitigated by proper control of anode/cathode stoichiometry, providing a guideline to optimize operating conditions of active DMFC systems.

Poly(tetrafluoroethylene- co -perfluoropropyl vinyl ether)-graft-poly(styrene sulfonic acid) (PFA- g -PSSA) membranes were prepared by γ -ray radiation-induced grafting of styrene onto 50 μm PFA films and a subsequent sulfonation. The properties of the PFA- g -PSSA membranes such as ion exchange capacity, water uptake, proton conductivity, and methanol permeability were evaluated and compared with commercial Nafion 115 membrane. The characteristic properties and direct methanol fuel cell (DMFC) performances with PFA- g -PSSA membrane were better than that with the Nafion 115 membrane. The power density of the single cell with PFA-PSSA30, PFA-PSSA50, PFA-PSSA80 membranes having different degree of grafting (DOG), and Nafion 115 membranes was 113, 123, 118, and 111 mW cm −2 at 0.4 V, respectively. To study the long-term durability of the prepared membrane electrode assembly (MEA) with a PFA-PSSA50 membrane, the single cell was tested for 2066 h in a galvanostatic mode under a constant load 150 mA cm −2 and at a temperature of 60 °C. The performance loss of the MEA after 2066 h operation was about 26.8%. Before and after the long-term performance test, the degradation of MEA with PFA- g -PSSA membrane was investigated by polarization curve technique, electrochemical impedance spectroscopy, TEM, X-ray diffraction, and ion exchange capacity.

Polymer electrolyte membranes have been widely investigated for high performance fuel cells. Here, we report the synthesis of ionic conductive Nafion/graphene oxide (GO) composite membranes for application in direct methanol fuel cells. GOs interact with both the non-polar backbone and the polar ionic clusters of Nafion because of their amphiphilic characteristics attributable to hydrophobic conjugation and hydrophilic functional groups. Accordingly, GO sheets serve to modify the microstructures of two domains of Nafion. In particular, the transport properties of Nafion are favorably manipulated by the incorporation of GO. This modulated the ionic channels of Nafion and decrease methanol crossover while preserving ionic conductivity. Furthermore, strong interfacial interactions due to the insertion of GO nanofillers into the Nafion matrix improve the thermal and mechanical properties of the material. In particular, we exploit Nafion/GO composite membrane as electrolyte material for direct methanol fuel cell (DMFC) in order to resolve current issue of methanol crossover. This composite membrane-based DMFC compared to the Nafion 112-based DMFC remarkably enhanced cell performance, especially in severe operating conditions.

Sulfonated polyethersulfones (sPES) with thermally crosslinkable allyl or propargyl endgroups were synthesized and evaluated as methanol-tolerant proton exchange membranes (PEMs) for use in a direct methanol fuel cell (DMFC). sPES with a controlled degree of sulfonation (DS) were generated by direct copolycondensation of sulfonated and nonsulfonated dichloro-monomers with bisphenol-A, and synthesis of crosslinkable sPES was completed by subsequent end group modification with allyl or propargyl halide. Dissolved polymers were simply cast to tough membranes that underwent thermal crosslinking at an elevated temperature. The final PEMs were obtained after further cation exchange of the membranes to generate the protonated form. The PEM films were rigorously characterized to elucidate their electrochemical and mechanical properties. It was found that the allyl-terminated sPES generally showed higher proton conductivity and methanol permeability than the propargyl-terminated counterparts with a similar DS, plausibly due to lower crosslinking reactivity of the allyl group relative to the propargyl groups. The allyl-terminated sPES was successfully fabricated into a membrane electrode assembly (MEA) by using sPES/Nafion mixed ionomers as the binder, and a power performance of 23.5 mW/cm2 was achieved in a DMFC single cell test in air-breathing semi-passive mode after activation for six days.

Freeze-thaw cycles were used to investigate performance degradation in direct methanol fuel cells (DMFC). The freeze-thaw cycles were carried out across the temperature range of −32 °C–60 °C. The details of the performance degradation were analyzed by comparing the change of polarization of each electrode and the electrochemical impedance spectrum according to the number of freeze-thaw cycles. It was found that freeze-thaw cycles caused the increase in the cathode overpotential to affect performance degradation and the increase in the charge transfer resistance which means distinct damages in the triple phase boundary of the catalyst layer. Different purging scenarios before freezing were adopted, namely the cathode purge and the anode–cathode purge, to reduce any performance degradation caused by the freeze-thaw cycles. The cells purged by nitrogen gas were found to have less performance loss than the cells that were not purged during the freeze-thaw cycles. The changes in the cell resistance and the cathode electrochemical surface areas were also smaller when the cells were purged compared with those cells that were not purged. The introduction of air purging had similar positive influences with nitrogen purging on the performance of the DMFCs and their impedance. It was also determined that air was better at purging only the cathode than purging both electrodes.

Strontium- and copper-doped lanthanum ferrite (LaSrCuFe) was used as new cathode material for solid oxide fuel cells (SOFCs) with scandia-stabilized zirconia electrolyte at intermediate temperatures. The performance of an anode-supported single cell prepared using a Ni/YSZ anode, ScMnSZ ((ZrO2)0.89(Sc2O3)0.1(MnO2)0.01) electrolyte, and a LaSrCuFe cathode was evaluated. The effects on the cell performance of the GDC (GD0.1Ce0.9O1.95) interlayer between the electrolyte and cathode were also investigated. The microstructure and chemical composition of the cell were analyzed using a scanning electron microscope (SEM) equipped with an energy dispersive X-ray analyzer (EDS). AC impedance spectroscopy was used to measure the polarization resistance of a single cell. The results highlight the promising combination of ScMnSZ electrolyte and LaSrCuFe cathode material in terms of chemical compatibility and electrical performance.

Various silica particles were adopted as catalyst supports, and silica-supported PtRu catalysts were evaluated as catalysts for the anode of direct methanol fuel cells at methanol concentrations of 1–10 M through single cell tests. Compared to a carbon black supported Pt–Ru catalysts, the silica-supported Pt–Ru catalysts exhibited higher performance in MEA, especially with high concentration over 3 M, and the maximum power density reached to 90 mW cm−2 and 60 mW cm−2 with 5 M and 10 M, respectively, which were 1.5 and 3 times higher than the reference carbon black supported catalysts. It was found that the silica particles as a catalyst support have a significant effect on reduction of methanol crossover and control of fuel feeding. Such a high performance in the operation with high concentrations was confirmed in the long-term durability test.

The outer micro-porous layer (MPL) between the gas diffusion layer and channel of the bipolar plate was studied for both sides of the electrodes in DMFC, with particular attention to the effects of the hydrophobicity of the MPL on mass transport as well as cell performance. Water-transport behavior from the electrodes to the channel was observed through the transparent window of the single cell with membrane-electrode assemblies (MEAs) including three combinations of outer MPLs. The crossover amount of methanol as well as water through the membrane was measured, and the mass balance, based on the measured flux, was established to understand the mass transport in MEAs. The design of outer MPLs is discussed for the best cell performance.

According to the conventional MEA test, methanol and water crossover are the main factors to determine performance of a passive DMFC. Thus, to ensure the high cell performance of a passive DMFC using high concentration methanol of 50–95 vol%, the MEA in this study introduces the barrier layer to limit the crossover of high concentration methanol, a hydrophobic layer to reduce water crossover, and a hydrophilic layer to enhance the water recovery from the cathode to the anode. The functional layers of the MEA have the effect of improving the performance of the passive DMFC by decreasing the methanol and water crossover. In spite of the operation with 95 vol% methanol, the MEA with multi-layer electrodes for high concentration methanol DMFCs shows a maximum power density of 35.1 mW cm−2 and maintains a high power density of 30 mW cm−2 (0.405 V) under constant current operation.

Highly dispersed Pd nanoparticles were prepared by borohydride reduction of Pd(acac)(2) in 1,2-propanediol at an elevated temperature. They were uniformly dispersed on carbon black without significant aggregation. X-ray diffraction showed that carbons from the Pd precursor dissolved in Pd, increasing its lattice parameter. A modified reduction process was tested to remove the carbon impurities. Carbon removal greatly enhanced catalytic activity toward the oxygen reduction reaction. It also generated an inconsistency between the electronic modifications obtained from X-ray photoelectron spectroscopy and the electrochemical method. CO displacement measurements showed that the formation of Pd-C bonds decreased the work function of the surface Pd atoms.

Scandia-stabilized zirconia (ScSZ) is a new candidate electrolyte for use in solid oxide fuel cells (SOFCs) at intermediate temperatures. ScMnSZ ((ZrO2)0.89(Sc2O3)0.1(MnO2)0.01) powders for the electrolyte were synthesized using the Pechini and ultrasonic spray pyrolysis (USP) methods. The electrical conductivities of sintered ScMnSZ samples prepared by the Pechini and USP methods are determined to be 0.112 and 0.091 S/cm, respectively, at 800 °C. An additional porous ScMnSZ electrolyte layer onto the dense electrolyte layer through a dip-coating process is a possible means of increasing the triple-phase boundary (TPB) of a cell. The performance of an anode-supported single cell prepared using a porous and dense composite electrolyte is superior to that of a cell with only the dense electrolyte.

cell DMFC stack was fabricated and operated with the load of 4 A for 4000 hrs. After 4000 hrs opera- tion peak power density of the stack reduced by 27.3%. Two of the five cells did now show performance degradation, the performance of other two was reduced by 40% and the performance of the other decreased by 60%. The amount of performance degradation of each cell by long-term operation did not correlate with the position in the stack. Platinum particle size in the anode catalyst layer of the MEA with the strongest degradation increased and the increase was severer on the position of methanol inlet than on the position of methanol outlet. However, platinum particle size in the cathode catalyst layers did not changed for all the MEA's. Ruthenium crossover from the anode catalyst layer to the cathode catalyst layer through the membrane was observed after 4,000 hrs operation by SEM-EDX and it occurred for all MEA's regardless of the degree of performance degradation. Atomic ratio of ruthenium to platinum in the cathode catalyst layer was the highest in the MEA with the strongest performance degradation

Carbon-supported Pt nanoparticles with various loading of Pt are prepared by a novel seed-mediated growth method using hydroquinone (HQ) assisted selective deposition. The structural and morphological dependence of the Pt nanoparticles on the catalytic activity in oxygen reduction reaction (ORR) is investigated. The analysis of core-level X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) cannot elucidate the origin of the large enhancement of the ORR activity. In contrast, electrochemical measurements of the CO-displacement charge and the concomitant CO adlayer oxidation behavior prove that the selective deposition of additional Pt contributed to the decrease of surface defects and to the increase of the onset potential for OH adsorption.

The influences of the gas diffusion layer (GDL) properties on the current distributions of a direct methanol fuel cell are investigated. Cathode GDLs with different hydrophobicity/hydrophilicity, air permeability, microporous layer (MPL), thickness, and texture properties are examined. Among the GDLs examined, a thin hydrophobic GDL with an MPL has the most homogeneous current distribution, which is primarily ascribed to the better water management capabilities of the cathode GDL properties. The differences in the current distribution among the different GDLs are more apparent when the air flow rate and loaded current are lower. The effect of the membrane thickness on the current distributions is also investigated. Among the membranes examined, Nafion ® 112 has different current distributions from the others, whereas there is no noticeable difference between the current distributions with Nafion ® 115 and Nafion ® 117. The current distribution with Nafion ® 112 is most affected by the enhanced methanol crossover and the high mixed potential.

In this study, 5 W class direct methanol fuel cell (DMFC) stacks using the flow field patterns of serpentine, parallel, and square spot are fabricated to compare how well they are capable of mass transport and water removal in the cathode. The stability of the stack is predicted through the simulation results of the flow field patterns on the pressure drop and the water mass fraction in the cathode of the stack. It is then estimated through the performance and the voltage distribution of the stack. According to the simulation results, although the square spot pattern shows the lowest pressure drop, the square spot pattern has much higher water mass fraction in the central region of the channel compared to the other flow field patterns. In accordance with the results, a square spot pattern for the stack-SSMA exhibits very poor water removal capabilities, leading to water flooding near the channel exit. In contrast, the performance stability of a stack-SPMA is comparable to the stack-SSMM.

Cold start and operation of a direct methanol fuel cell (DMFC) are investigated at sub-zero temperatures by using a 10-cell stack. The stack is manufactured with a hydrocarbon membrane to minimize the methanol crossover problem, which can be caused by use of high concentration methanol solutions. The stack is heated up for the cold start and operation only by heat of the exothermic reactions without any heating device and additional insulation means, to examine operation characteristics of the DMFC stack at low temperatures. The concentration of methanol solutions is selected in the range of 3–8 M, considering the freezing points of the solution for corresponding operation temperatures (−5 to −15 °C). Although the DMFC stack undergoes a sharp voltage drop and a significant performance decrease at the initial stage of the frozen condition, the self-heating DMFC are successfully operated at −5 and −10 °C in both constant current or constant voltage modes. The cold start-up time also is nearly independent of the operating modes. In contrast, the stack at −15 °C is barely started up only by a constant voltage mode with some voltage fluctuation. The DMFC stack after the cold operation exhibits the performance loss of about 45%. Such performance loss is mainly caused by degradation of the electrocatalysts.

In this study, STS 316L (Stainless Steel 316L), STS 430, and Ti metal are investigated as metal bipolar plates for a direct methanol fuel cell (DMFC). The corrosion resistance of these materials is investigated by potentiodynamic and chronoamperometry tests. Their cell performance and long-term stability are then studied under a real fuel cell test. The corrosion resistance of the metal bipolar plates is in the order of Ti > STS 316L > STS 430. However, the results of the real fuel cell test differ from the results of the corrosion resistance. Ti shows the lowest performance due to a sharp performance decrease in ohmic loss regions, while STS 430 shows a lower performance decrease in ohmic loss regions. Although STS 430 has less resistance to corrosion than STS 316L in the simulated environment, STS 430 performs better as a metal bipolar plate for a DMFC than STS 316L, particularly, with regard to cell performance, cell resistance, and durability.

A new and efficient synthetic approach to biologically interesting geranylated flavanones and geranylated chalcones is described. Thus, the first total syntheses of the geranylated flavanones (±)-prostratol F (1), (±)-8-geranyl-3′,4′,7-trihydroxyflavanone (2), and (±)-6-geranyl-5,7-dihydroxy-3′,4′-dimethoxyflavanone (3) were carried out starting from 2,4-dihydroxyacetophenone (10) and 2,4,6-trihydroxyacethophenone (17) in five to six steps (Schemes 2 and 3). The geranylated chalcones xanthoangelol (4), 3-geranyl-2,3′,4,4′-tetrahydroxychalcone (5), (±)-lespeol (6), and lespeol derivatives (±)-7–9 were synthesized starting from 2,4-dihydroxyacetophenone (10) in three to four steps (Schemes 2 and 6).

The influences of various operating conditions on the current distribution of a direct methanol fuel cell with flow-fields of serpentine channels are investigated by means of a current-mapping method. The current densities generally deviate more from an even distribution when the cell temperature or flow rate of the cathode reactant is lower, or when the current loaded on the cell or the methanol concentration is higher. In addition, uneven current distributions decrease the cell performance. Relevant mass-transfer phenomena such as water flooding and methanol crossover are discussed. The characteristics of the channel configuration also affect the current density profiles. With a five-line serpentine channel, the current densities are lowered periodically where the flow direction is inverted due to the corner flow effect and the subsequent water accumulation. With a single serpentine channel, on the other hand, the current densities peak periodically where the flow direction is inverted due to enhanced air convection through the gas-diffusion layer.

‡Efficient one-pot synthesis of arylmethylene bis(3-hydroxy-2-cyclohexene-1-ones) and xanthenediones by EDDA and In(OTf)3-catalyzed reactions was developed starting from dimedone and aryl aldehydes. The key strategies of these reactions involve domino Knoevenagel/Michael reaction or Koevenagel/Michael/Cyclodehydration reactions. The scope and limitation of the two catalysts under various reaction conditions were investigated and described.

레독스 흐름 전지의 전극으로 사용하기 위해 탄소펠트를 열처리와 산처리 방법으로 산화 개질하였다. 열중량 분석결과 열처리 또는 산처리에 의하여 탄소펠트의 섬유 표면에 고분자 물질이 제거되고 산소 관능기가 도입된 것을 확인할 수 있었으며 습식 방법인 산처리 방법보다 건식방법인 열처리 방법이 기계적 안정성을 유지하는데 효과적인 처리 방법으로 나타났다. XPS, 원소분석을 통하여 500 $^{\circ}C$ 에서 4시간 열처리한 탄소펠트의 표면에 산소 관능기가 부가된 것을 확인하였으며 질소흡착실험에서 거의 없던 표면적이 96 $m^2/g$ 로 증가한 것을 알 수 있었다. CV실험 및 분극 실험을 수행한 결과 500 $^{\circ}C$ 열처리 전극의 활성화 저항이 가장 낮게 나타났다. 산처리한 탄소펠트와 400 $^{\circ}C$ , 500 $^{\circ}C$ 에서 열처리한 탄소펠트를 이용하여 바나듐 레독스 흐름 전지를 구성하고 충/방전 실험을 실시한 결과 충/방전 전압효율이 산처리 전극의 경우 86.6%, 400 $^{\circ}C$ 열처리 전극의 경우 89.6%, 500 $^{\circ}C$ 열처리 전극의 경우 90.6%로 500 $^{\circ}C$ 열처리 전극이 가장 우수하였다. 【Carbon felt surface was modified by heat or acid treatment in order to use for the electrode of a redox-flow battery. Polymers on the surface of carbon felt was removed and oxygen-containing functional group was attached after the thermal treatment of carbon felt. Thermal treatment was better for the stability of the carbon structure than the acid treatment. Oxygen-containing functional group on the thermally treated carbon felt at 500 $^{\circ}C$ was confirmed by XPS and elementary analysis. BET surface area was increased from nearly zero to 96 $m^2/g$ . Thermally treated carbon felt at 500 $^{\circ}C$ showed lower activation polarization than the thermally treated carbon felt at 400 $^{\circ}C$ and the acid-treated carbon felt in the cyclicvoltammetry and polarization experiments. The thermally treated carbon felts at 400 $^{\circ}C$ and 500 $^{\circ}C$ and the acid-treated carbon felt was applied for the electrode to prepare vanadium redox flow battery. Voltage efficiencies of charge/discharge were 86.6%, 89.6%, and 96.9% for the thermally treated carbon felts at 400 $^{\circ}C$ and 500 $^{\circ}C$ and the acid-treated carbon felt, respectively.】

A versatile, facile, and rapid synthetic method of advanced carbon nanotube (CNT)-based nanohybrid fabrication, or the so-called ionic-liquid-assisted sonochemical method (ILASM), which combines the supramolecular chemistry between ionic liquids (ILs) and CNTs with sonochemistry for the control in the size and amount of uniformly decorated nanoparticles (NPs) and interfacial engineering, is reported. The excellence in electrocatalysis of hybrid materials with well-designed nanostructures and favorable interfaces is demonstrated by applying them to electrochemical catalysis. The synthetic method discussed in this report has an important and immediate impact not only on the design and synthesis of functional hybrid nanomaterials by supramolecular chemistry and sonochemistry but also on applications of the same into electrochemical devices such as sensors, fuel cells, solar cells, actuators, batteries, and capacitors.

In order to develop a novel polymer electrolyte membrane for direct methanol fuel cell (DMFC), styrene monomer was graft-polymerized into poly(tetrafluoroethylene perfluoropropyl vinyl ether) (PFA) film followed by a sulfonation reaction. The graft polymerization was prepared by the -ray radiation-grafting method. Subsequently, sulfonation of the radiation-grafted film was carried out in a chlorosulfonic acid/1,2-dichloroethane (2 v/v%) solution. The chemical, physical, electrochemical and morphological properties of the radiation-grafted membranes (PFA-g-PSSA) were characterized by fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The water uptake, ionic conductivity, and methanol permeability of the PFA-g-PSSA membrane were also measured. The cell performances of MEA prepared with the PFA-g-PSSA membranes were evaluated and the cell resistances were measured by an impedance analyzer. The MEA using PFA-g-PSSA membranes showed superior performance for DMFCs in comparison with the commercial Nafion 112 membrane.

Vapor-grown carbon fibers (VGCFs) were added to the anode catalyst layer of a direct methanol fuel cell to improve the cell performance through structural modification of the catalyst layer. The amount of VGCF varied up to 6 wt.% with respect to the weight of the PtRu black catalyst that was used. A catalyst layer with 2 wt.% VGCF loading showed the best cell performance. The electrodes that included the catalyst, VGCF, and gas diffusion layer, were directly examined by electron microscopic analyses. Electrochemical methods, such as cyclic voltammometry and impedence analysis, were applied to investigate the actual role of VGCF in the electrode. The porosity of the catalyst layer was increased by the addition of the fibers. This was clearly observed in pore diameters less than 1 μm. Sub-micron pore diameters are significant as they relate to micro-diffusive transport, compared to the macro-diffusion experienced by the large pores in the GDL. However, improved mass transport was only observed for 2 wt.% VGCF loading, probably due to insufficient optimization of the cell design. Microstructural and electrochemical analyses indicated that the improved performance was mainly ascribed to an increased electrochemically active surface area of the catalyst.

We modified Nafion by means of chemical in situ polymerization of pyrrole monomers with platinum (Pt) precursors for an application into an electrolyte of direct methanol fuel cells (DMFCs). SEM and EPMA exhibited the presences of polypyrrole and Pt at the surface region of Nafion, after diffusing and polymerizing pyrrole monomers with Pt precursors. XPS and FT-IR spectra were used to characterize the surface of Naf–Ppy–Pt composite membranes, demonstrating that pyrrolinum groups of polypyrrole were interacted with sulfonic groups or Pt precursors (PtCl 6 − or PtCl 4 − ). After in situ polymerization of pyrrole monomers, the morphological reorganization of sulfonic groups in Naf–Ppy–Pt composite membranes occurred via electrostatic interaction. Thermal stability, proton conductivity, methanol permeability, and cell performance of composite membranes were analyzed by TGA, AC impedance, refractometer, and potentiostat. Naf–Ppy–Pt composite membranes had higher thermal stabilities of sulfonic groups and side chains than Nafion and Naf–Ppy as a result of the interaction between Nafion–SO 3 − ⋯polypyrrole–NH 2 + and the presence of thermally stable Pt. The cell performance of Naf–Ppy–Pt 0 0 2 was enhanced significantly compared to that of Nafion under the specific condition, due to more reduction of methanol crossover than that of proton conductivity. Therefore, this synthetic method offers a facile way to improve physical properties of polymer electrolyte for the fabrication of advanced composite membranes.

Understanding the exact structure and surface characteristics of carbon materials is very important for design, synthesis, and utilization of the best carbon form with particular functions and high performance for practical applications such as selective adsorption adsorbents, energy storage materials, catalysts or catalyst supports, etc. This review paper focuses on carbon surface properties and the interaction between gaseous or liquid substances and carbon surface. Catalytic functions of carbon materials are reviewed including recent progress in synthesis and applications of nano-carbons. Keywords : Carbon catalysts, Catalyst supports, Adsorption, Surface properties

PtRu/C catalysts were prepared using an aqueous co-impregnation method with NaBH 4 as a reducing agent. In order to investigate the effect of the reducing agent concentration, metal ions were reduced in different NaBH 4 concentrations for which the molar ratios of NaBH 4 to metal ions were controlled to 1, 2, 5, 15, 50, and 250. The electrochemical properties were studied by cyclic voltammetry in a 0.5 M H 2 SO 4 solution. The surface compositions and oxidation states of the catalysts were observed by X-ray photoelectron spectroscopy (XPS). According to the X-ray diffraction (XRD) results, Pt (fcc) peak shifts were observed and crystal sizes were calculated. The electro-catalytic activities of the prepared catalysts for methanol electro-oxidation were estimated using linear sweep voltammetry. Unit cell tests were carried out to compare the direct methanol fuel cell performances. The NaBH 4 concentration was found to affect the dispersion and the surface composition of the prepared PtRu particles. Optimum molar ratios of NaBH 4 to metal ions were 5 and 15 for methanol electro-oxidation.

A Pt-layer was deposited on the anode side of a Nafion membrane via a sputtering method in order to reduce methanol crossover in a direct methanol fuel cell (DMFC). The methanol permeation and the proton conductivity through the modified membranes were investigated. The performances of the direct methanol fuel cell were also tested using single cells with a Nafion membrane and the modified membranes. The Pt-layers on the membrane blocked both methanol crossover and proton transport through the membranes. Methanol permeability and proton conductivity decreased with an increase of the platinum layer thickness. At methanol concentration of 2 M, the DMFC employing the modified membrane with a platinum layer of 66 nm-thickness showed similar performance to that of a DMFC with a bare Nafion membrane in spite of the lower proton conductivity of the former. The maximum power density of the cell using the modified membrane with a platinum layer of 66 nm-thickness increased slightly while that of the cell with the bare membrane decreased abruptly when a methanol solution of 6M was supplied.

The composite membrane for direct methanol fuel cell (DMFC) was developed using powder and perfluorosulfonylfluroride copolymer (Nafion) resin. The perfluorosulfonylfluroride copolymer (Nafion) resin was mixed with powder and it was made to sheet form by hot pressing. The electrodes were prepared with 60 wt% PtRu/C and 60wt% Pt/C catalysts for anode and cathode, respectively. The morphology and the chemical composition of the composite membrane have been investigated by using SEM and EDXA, respectively. The composite membrane and were analyzed by using FT-IR and XRD. The methanol permeability of the composite membranes was also measured by gas chromatography (GC). The performance of the MEA containing the composite membrane (2wt% ) was higher than that of normal pure Nafion membrane at high operating temperature (e.g. ), due to the homogenous distribution of , which decreased the methanol permeability through the membrane and enhanced the water contents in the composite membrane.