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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

Porous carbon nanofibers(CNF) were synthesized via NaOH activation at 700~, and the porous CNF-supported PtRu catalysts were evaluated for the anode in direct methanol fuel cells. The change of surface characteristics by NaOH activation was examined by analyses of the specific surface area and pore size distribution. The morphological and structural modification was investigated under scanning electron microscopy. The activity of catalysts supported on porous CNFs was examined by cyclic voltammograms and single cell tests. The pore formation on CNF by the NaOH activation was discussed, concerning the catalyst activity, when they were applied as catalyst supports.

In this work, we studied the characteristic variations of catalyst supports caused by mechanical milling and their electrochemical application in fuel cells. Two different catalyst supports, carbon black (XC-72R) and K20 (mesoporous carbon), were crushed and dispersed by mechanical milling using a bead mill. The bead mill operated with 0.3 μm zirconia beads at the rate of 3500 rpm for 30 min. The secondary particle size of the crushed catalyst supports ranged from around 0.1 μm to 10 μm. The secondary particle size of the catalyst supports after crushing represents a decrease of approximately 10% compared with that of raw catalyst supports. To confirm the role of the catalyst supports in the direct methanol fuel cell (DMFC), Pt and Ru were loaded onto these catalyst supports using an impregnation method. In the single cell test, Pt–Ru/XC-Bead and PtRu/K20-Bead showed power densities of 135 mW/cm2 and 144 mW/cm2 under air at 60 °C, respectively. The performance values of these catalysts, which were fabricated using reformed catalyst supports, were 10% to 20% higher than those of raw catalyst supports. As a result, the catalyst supports crushed by the bead mill helped to improve the electrochemical performance of the direct methanol fuel cell.

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.

CrN/Cr-coated stainless steel (STS) 316L is investigated as the material for a metal bipolar plate for a direct methanol fuel cell (DMFC) under actual operating circumstances. Protective coating layers of CrN/Cr are formed on STS 316L using an unbalanced magnetron (UBM) DC sputter via Cr target in an effort to improve the corrosion resistance and long-term stability of the STS 316L. In a corrosion resistance test, the CrN/Cr-coated STS 316L shows much better corrosion resistance than bare STS 316L in simulated electrolytic environments under anodic and cathodic potentials relevant to DMFCs. The interfacial contact resistance (ICR) between CrN/Cr-coated 316L and carbon paper decrease to 4 mΩ cm2 at a compaction force of 150 N cm−2 compared to bare STS 316L (570 mΩ cm2). The CrN/Cr-coated STS 316L cell has better cell performance compared to the bare STS 316L cell. Furthermore, the CrN/Cr-coated STS 316L cell exhibit low voltage losses of 38.2 μV h−1 under long-term operation of 760 h. These results show that the CrN/Cr-coated STS 316L, demonstrating its feasibility for use as a metal bipolar plate in a DMFC under actual operating circumstances.

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.

Water flooding phenomena in the cathode of direct methanol fuel cells were analyzed by using electrochemical impedance spectroscopy. Two kinds of commercial gas diffusion layers with different PTFE contents of 5 wt% (GDL A5) and 20 wt% (GDL B20) were used to investigate the water flooding under various operating conditions. Water flooding was divided into two types: catalyst flooding and backing flooding. The cathode impedance spectra of each gas diffusion layer was obtained and compared under the same conditions. The diameter of the capacitive semicircle became larger with increasing current density for both, and this increase was greater for GDL B20 than GDL A5. Catalyst flooding is dominant and backing flooding is negligible when the air flow rate is high and current density is low. An equivalent model was suggested and fitted to the experimental data. Parameters for catalyst flooding and backing flooding were individually obtained. The capacitance of the catalyst layer decreases as the air flow rate decreases when the catalyst flooding is dominant.

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.

This study examines the operating characteristics and durability of a small direct methanol fuel cell (DMFC) stack (volume: 39.6 cm 3 ). To investigate the operating characteristics in a real multi-user operating mode, various load cycles (such as gradual acceleration and deceleration), two operating modes (current mode or voltage mode) and four interrupted operating methods (load on–off, load–methanol on–off, load–air on–off, and load–methanol–air on–off) are used. The durability of the DMFC stack is examined at a constant voltage of 2.4 V (0.4 V per cell) by using the load–methanol–air on–off mode for more than 2000 h. In these tests, the DMFC stack exhibits a rapid, stable and dynamic response regardless of the load cycle and operating mode, though the stack performance and response behaviour vary with the interrupted operating modes. Among the operating modes, the air-interruption modes exhibit better stability and higher performance. Moreover, the load–methanol–air on–off mode provides the stack with good durability and a high performance in a long-term test of 2045 h.

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.

Particularly channeled carbon nanofibers (CNF) were applied to the catalyst support for preparation of electrode catalysts for DMFC. Porous CNFs were prepared through selective gasification of CNF with nano-sized catalyst particles such as Ru under prescribed conditions. The channel width, length, and channeling direction were dependent on the catalyst nature and preparation conditions. The channeled CNFs-supported PtRu catalysts were tested in methanol oxidation and DMFC single cells.

In this study, we investigated the austenitic stainless steel 316 and the ferritic stainless steel 430, 446, and pure Ti plate as metal bipolar plates for direct methanol fuel cell (DMFC). This work was carried out to offer fundamental information about metal bipolar plates for DMFC. All corrosion tests were performed in 0.001 M H2SO4 solution containing 2 ppm F in order to simulate the fuel cell environment. The potentiodynamic polarization curves were measured by an electrochemical analysis instrument (ZAHNER, IM6&IM6eX) including a potentiostat. The scanning range was from -0.8 V to 1.2 V and the scanning rate were 2 mV/s. Chronoamperometry test in which the cell was operated at the same operational potentials, 0.4 V and 0.8 V versus NHE were chosen as test potential. The single cell performance and long-run test of more than 1000 hr were tested at real operating conditions of DMFC. During these lifetime tests, the cell resistance, polarization curve, anode polarization and ac impedance were periodically measured to investigate a direct cause of the performance degradation of the cells with operating time. In addition, scanning electron microscopy (SEM) was used to investigate the morphology of metal bipolar plates after and before the long-term test. Composition of the corroded oxides was confirmed using energy dispersive spectroscopy (EDS) and metal contaminants were analyzed by inductively coupled plasma atomic emission spectrometer (ICPAES)

‡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.

A reciprocating pump operated by a piezoelectric linear actuator is introduced as a fuel supplying module for a DMFC. A series of experiments are conducted to characterize the performance of the present pump and effects of low reciprocating frequency pumping of fuel on output power of DMFC. The performance of the pump is studied with respect to reciprocating frequency and operating duty. The results show that the key advantage of the current pump is an ability of low frequency operation which enables high flow rectification performance and that power consumption of the pump is almost linearly proportional to the flow rate. It is also shown that the output voltage of the DMFC is stable with time even though the pumping pressure oscillates periodically

We have developed very small direct methanol fuel cell stack for mobile devices. The stack was designed with the total size of 48 mm × 50 mm × 17 mm (volume: ~ 40.8 cc) and it consisted of 6 cells and each cell has an active area of 13.7 cm2. The maximum power output of the stack is 7.63W (1.81V @ 4.22A) and the nominal power output of the stack was 5.49W (2.4V @ 2.29A) at 2.4V (0.4 V/cell). In this work, we studied starting characteristics of 5W class small DMFC stack and effects of methanol/air stoichiometry on the stack performance at constant current.

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.

The characteristics of a platinum–ruthenium catalyst supported on porous carbon (PC) are analysed by X-ray diffraction, scanning electron microscopy, cyclic voltammetry and chemisorption techniques. Single-cell tests are carried out in order to compare the performance of these catalysts as an anode in a direct methanol fuel cell with respect to that of a commercial-grade catalyst. The methanol oxidation rate on a Pt–Ru catalyst supported on PC with a pore size of 20 nm is about 35% higher than that on a commercial E-TEK catalyst. The catalyst (Pt–Ru/K20) in the single-cell test gives a power density of 90 and 126 mW cm −2 under air and oxygen at 60 °C, respectively. These values are 15–16% higher than those obtained with a commercial E-TEK catalyst.

This study examined methanol crossover through PtRu/Nafion composite membranes for the direct methanol fuel cell. For this purpose, 0.03, 0.05 and 0.10 wt% PtRu/Nafion composite membranes were fabricated using a solution impregnation method. The composite membrane was characterized by inductively coupled plasma-mass spectroscopy and thermo-gravimetric analysis. The methanol permeability and proton conductivity of the composite membranes were measured by gas chromatography and impedance spectroscopy, respectively. In addition, the composite membrane performance was evaluated using a single cell test. The proton conductivity of the composite membrane decreased with increasing number of PtRu particles embedded in the pure Nafion membrane, while the level of methanol permeation was retarded. From the results of the single cell test, the maximum performance of the composite membrane was approximately 27% and 31% higher than that of the pure Nafion membrane at an operating temperature of 30 and 45 °C, respectively. The optimum loading of PtRu was determined to be 0.05 wt% PtRu/Nafion composite membrane.The PtRu particles embedded in the Nafion membrane act as a barrier against methanol crossover by the chemical oxidation of methanol on embedded PtRu particles and by reducing the proton conduction pathway.

Carbon nanofiber (CNF) grown catalytically was chemically activated with KOH to attain structural change of CNF. The structural changes of CNF through KOH activation were investigated by using BET and SEM. From the results of BET, it was found that KOH activation was effective to develop particular sizes of pores on the CNF surface, increasing the surface area of CNF. Activated CNF was applied as an anode catalyst support of fuel cell. The effects of different activation conditions including the activation temperature and the activation time on the specific surface area of the CNF activated with KOH were investigated to obtain appropriate structure as a catalyst support. The 60 wt% Pt-Ru catalyst prepared was observed by using TEM and XRD.

Pore-size controlled porous carbons were prepared for the catalyst-supporting materials of direct methanol fuel cell (DMFC) from the naphthalene-based mesophase pitch. Porous carbon was synthesized by etching the silica sphere from the carbon/silica mixture. The pore size of the porous carbon was controlled by the size of silica sphere. 60wt% Pt-Ru/porous carbons catalysts were prepared by using impregnation method. Physical and electrochemical properties of the catalyst were characterized by using XRD, cyclic voltammetry (CV) and unit cell test.

Three-dimensional computational simulation was employed to illustrate the performance characteristics according to the flow-field design by solving the physics in the flow field and the diffusion layer and by calculating the electrochemical reaction at the catalyst layer. The pressure loss and the concentration distribution in the anode were analyzed for four types of flow field, parallel, serpentine, parallel serpentine and zigzag type. Also the anode current density distribution was predicted at the various overpotentials. The cell performance was proportional to the pressure drop for all the flow-field types. Zigzag type showed the best performance which has a good resistance against the fuel concentration polarization and the next was serpentine.

Direct borohydrides fuel cell (DBFC) was emerged to complement the problem of DMFC`s low performance and methanol crossover to the cathode and to apply the fuel cell to portable and mobile devices. In this study, the characteristics of novel catalysts was tested to establish the electrode preparation process of DBFC. Pt black and carbon supported-Pt by paste method were used as the cathode catalysts. Pt black, carbon supported-Au and alloy were used as the anode catalysts. The characteristics of the electrodes were analyzed by XRD, SEM, EDS. The performance test of single cell using the electrodes were carried out in order to evaluate the electrode performance. In the result, the maximum power output was obtained as 366 mW/mg when using Pt/C as anode and cathode catalysts

We developed induction furnace brazed anode supported tubular and flat tube SOFCs to improve power density and studied basic technology of key components for making stacks from them. Performance of the flat tube cell showed 210 mW/cm 2 (0.7y 300 mA/cm 2 ) at 750°C. Induction furnace brazing was applied to connect ceramic and metal parts and their gas permeability was tested. The results indicated that the induction furnace brazing method could be used effectively for making anode supported tubular and flat tube cell stack. Through these experiments, we obtained basic technology of such cells and established a proprietary concept of the anode-supported tubular and flat tube cell stack.

This study was carried out to develop a direct methanol fuel cell (DMFC)/battery hybrid power system used in portable applications. For a portable power system, the DMFC was applied for the main power source at average load and the battery was applied for auxiliary power at overload. Load share characteristics of hybrid power source were analyzed by computational simulation. The connection apparatus between the DMFC and the battery was set and investigated in the real system. Voltages and currents of the load, the battery and the DMFC were measured according to fuel, air and load changes. The relationship between load share characteristic and battery capacity was surveyed. The relationship was also studied in abnormal operation. A DMFC stack was manufactured for this experiment. For the study of the connection characteristics to the fuel cell Pb-acid, Ni–Cd and Ni–MH batteries were tested. The results of this study can be applied to design the interface module of the fuel cell/battery hybrid system and to determine the design requirement in the fuel cell stack for portable applications.

Direct methanol fuel cells (DMFC) have major technical problems, e.g. slow methanol oxidation kinetics and high methanol crossover, to use as power sources for several applications. To overcome these problems it has been proposed to increase the fuel cell operating temperature to over 100–150 °C and to reduce the methanol permeability. In this work, we made Nafion ® /montmorillonite (MMT) nanocomposite membranes and carried out diverse tests. The nanocomposite membranes were produced by direct melt intercalation of perfluorosulfonylfluoride copolymer resin (Nafion ® resin) into the montmorillonite and modified montmorillonite (m-MMT) which was organized by dodecylamine. The membrane–electrode assembly (MEA) has been made using a hot pressing method and the electrode prepared using PtRu black and Pt black catalysts for anode and cathode, respectively. The morphology of the nanocomposite membranes has been investigated using SEM and TEM. The nanocomposite membranes and MMT and m-MMT were analyzed using by FT-IR and X-ray diffraction (XRD). The thermal and mechanical properties of those membranes were also investigated and the methanol permeability was measured by gas chromatography (GC). The performance of the MEA using the nanocomposite membrane was evaluated by single cell test. The results show that the performance of the MEA using the nanocomposite membrane was higher than that of a commercial Nafion ® membrane at high operating temperature.

For the development of low temperature anode-supported planar solid oxide fuel cell, the planar anode supports with the thickness of 0.8 to 1 mm and the area of 25, 100 and were fabricated by the tape casting method. The strength, porosity, gas permeability and electrical conductivity of the planar anode support were measured. The porosity of anode supports sintered at and then reduced in atmosphere was increased from . The electrical conductivity of the anode support was and its gas permeability was 6l/min at 1 atm in air atmosphere. The electrolyte layer and cathode layer were fabricated by slurry dip coating method and then had examined the thickness of and the gas permeability of 2.5 ml/min at 3 atm in air atmosphere. As preliminary experiment, cathode multi-layered structure consists of LSM-YSZ/LSM/LSCF. At single cell test using the electrolyte layer with thickness of 20 to , we achieved and 0.6V at

The performance of the Direct Methanol Fuel Cell (DMFC) using multi-layer electrode, which prepared by various anode catalysts and Nafion membranes, was studied for reducing the amount of the metal catalyst loaded in the MEA system. The amount of the catalyst used in this experiment was in cathode and in anode, respectively. The best performance was to be of MEA3 at and 2 bar in this experiment. However, the overall performance of the DMFC was maintained almost the same compared to the general commercial catalyst systems.

Upgrading low-rank coal (LRC) through various strategies is always an important issue. Here, we report the production of hybrid coals and an evaluation of their characteristics for use as a fuel in power plants. The hybrid coals (HCKs) were prepared by a combination of drying and biomass impregnation into an Indonesian LRC followed by a pre-carbonization process. We used a top-spray fluidized-bed reactor for drying, biomass impregnation, and pre-carbonization to produce hybrid coals that have improved fuel characteristics in terms of heating value, moisture re-adsorption, and combustion patterns. A systematic study reveals that experimental parameters, such as a bed temperature, bioliquid spraying procedure and pre-carbonization temperature strongly influence the characteristics of the resulting hybrid coal, meaning that they have an important role in upgrading LRC. In particular, the hybrid coal prepared by a process of simultaneous drying and bioliquid spraying followed by pre-carbonization at 200 ∼ 300°C showed high contents of fixed carbon, an improved heating value, lower moisture adsorption, and single combustion patterns in which the characteristics were dramatically upgraded for practical use as a fuel in power plants. In addition, the simultaneous process using a fluidized-bed reactor has great potential because it can achieve process simplification, reduce manufacturing costs, and handle coal particles easily.

The displacement of carbon black to polypyrrole as a catalyst supporter in the fuel electrode of a direct methanol fuel cell was investigated. Polypyrrole was obtained as a black powder by the chemical polymerization of pyrrole with three different oxidants. The synthesized polypyrroles were pasted on carbon paper and transformed to the fuel electrodes with electrochemically deposited platinum. The prepared fuel electrode was assembled and mounted in a unit cell using a membrane and cathodic electrode film. In comparison with the carbon black fuel electrode, the performance of the unit cell was analyzed in relation to the state of the catalyst, the type of oxidant, and the morphology of the polypyrrole powder.

Nafion/silicon oxide composite membranes were produced via the in situ acid-catalyzed sol–gel reaction of tetraethylorthosilicate (TEOS) in Nafion perfluorosulfonic acid films. The TEOS uptake content of a composite membrane was varied according to the sol–gel reaction time. The physicochemical properties of the composite membranes were investigated by FT-IR. The water uptake contents and the thermal properties of the composite membrane were analyzed by DSC–TGA. The performance of a membrane–electrode assembly (MEA) using the composite membrane was evaluated by single cell test and methanol permeability was measured by gas chromatography (GC). The results show that the performance of a MEA using the composite membrane was higher than that of a commercial membrane at high temperature.

Ru and RuO 2 composite films were deposited on TiN/Ti/Si substrate by metal-organic chemical vapor deposition (MOCVD) for application as the bottom electrode of a high density DRAM capacitor. The effects of iodine sources (CH 3 I, C 2 H 5 I) on composite films deposited at 300 °C were investigated. Iodine sources enhanced nucleation dramatically at the initial deposition stage, and the surface roughness of the films was reduced considerably. The root-mean-square (r.m.s.) surface roughness of composite films that were grown up to 1000 A with no addition, CH 3 I and C 2 H 5 I were 162, 48 and 38 A, respectively. Moreover, iodine sources did not affect the orientation or deposition rate of films.

A critical issue for maintaining long-term applications of polymer electrolyte fuel cells (PEFCs) is the development of an innovative technique for the functionalization of a carbon support that preserves their exceptional electrical conductivity and robustly enriches their durability. Here, we report for the first time how the formation of a partially coated, ultrathin, hydrophobic silica layer around the surfaces of the carbon nanofiber (CNF) helps improve the durability of the CNF without decreasing the significant electrical conductivity of the virgin CNF. The synthesis involved the adsorption of polycarbomethylsilane (PS) on the CNF's sidewalls, followed by high temperature pyrolysis of PS, resulting in a highly durable, conductive carbon support in PEFCs. The Pt nanoparticles are in direct contact with the surface of the carbon in the empty spaces between unevenly coated silica layers, which are not deposited directly onto the silica layer. The presence of a Pt nanoparticle layer that was thicker than the silica layer would be a quite advantageous circumstance that provides contact with other neighboring CNFs without having a significant adverse effect that deeply damages the electrical conductivity of the neighboring CNF composites with the silica layer. Furthermore, the ultrathin, hydrophobic silica layer around the surfaces of the CNF provides great potential to reduce the presence of water molecules in the vicinity of the carbon supports and the ˙OH radicals formed on the surface of the Pt catalyst. As a result, the CNF with a 5 wt% silica layer that we prepared has had extremely high initial performance and durability under severe carbon corrosion conditions, starting up with 974 mA cm(-2) at 0.6 V and ending up with more than 58% of the initial performance (i.e., 569 mA cm(-2) at 0.6 V) after a 1.6 V holding test for 6 h. The beginning-of-life and end-of-life performances based on the virgin CNF without the silica layer were 981 and 340 mA cm(-2) at 0.6 V, respectively. The CNF having a silica layer had long-term durability which was superior to that of the virgin CNF.

A sulfonated styrene-(ethylene-butylene)-sulfonated styrene (SEBSS) is a highly sulfonated random block polymer. This material has several characteristics including high proton conductivity, good mechanical properties, and relatively low cost, but the chemical and temperature stability is lower than that of perfluorinated polymers such as Nafion® due to lower C–H bond association enthalpies of the hydrocarbon framework in polymer. In this paper, we developed the chemical and temperature stability of sulfonated styrene polymer membrane by impregnating silica in these polymers in order to overcome the humidification constraints in direct methanol fuel cell (DMFC). We modified a composite membrane by including a small amount of silica with the aim of retaining the electrochemically produced water inside the cell. A composite sulfonated SEBSS membrane was synthesized by the blending of inorganic materials such as tetraethylorthosilicate. Membrane cast from this material was investigated in relation to methanol permeability in the range of methanol concentration from 2 to 4 M at 30°C. SEM Photograph revealed a brittle, surface-attached silica layer with silicon oxide contents. The thermal decomposition of a composite membrane was investigated by TG-DSC thermograms. The I–V characteristics of DMFC using a composite membrane as electrolyte was studied with a single cell test equipment at the temperature of 30–90°C. The highest current densities are 74, 229, and 442 mA / cm 2 at temperatures 30, 60, and 90°C at a potential of 0.3 V , when small amounts of silica of 0.014 mol was added to SEBSS polymer.

The electrooxidation of methanol on Pt–Ru catalyst supported by basal plane graphite was investigated in phosphoric acid solution by cyclic voltammetry, X-ray diffraction (XRD) and scanning electron microscope (SEM). Pt–Ru catalysts were prepared by applying a potential of 0.0 V in chloroplatinic acid solution of various ruthenium chloride concentrations. The peak potential of methanol oxidation is shifted to a lower potential as the concentration ratio of Ru/Pt in the electrodeposition solution. Shifts of peak potential are due to the difference of the oxidation pathway of CO adsorbed on the surface of Pt–Ru catalyst. For methanol oxidation in phosphoric acid solution, the electrocatalytic activity of the catalyst prepared in ruthenium chloride solutions of chloroplatinic acid solution (1:1) was better than that of catalysts prepared in different concentrations of ruthenium chloride solution.

The performance of a direct methanol fuel cell based on a polymer electrolyte membrane electrolyte was investigated. Pt–Ru/C (60 wt.%) and Pt/C (60 wt.%) catalysts were employed for methanol oxidation and oxygen reduction, respectively. Morphology of the catalysts was investigated using X-ray powder diffraction, electron diffraction patterns and transmission electron microscopy. I–V characteristics of the fuel cell were tested by changing the methanol concentration, temperature, and Nafion types as a polymer electrolyte membrane electrolyte. The performance of the single cell was enhanced by increasing cell temperature. High cell voltage was obtained from 2.5 M methanol. The cell fabricated with Nafion 112 membranes with a current density of 230 mA/cm 2 at 0.55 V was obtained from 2.5 M methanol. Heat-treating of the Pt-Ru/C catalyst at 500°C for 4 h affected the performance of the direct methanol fuel cell (DMFC) single cell resulting in particle agglomeration and crystal growth.

An easy method to synthesize SiOx coated carbon nanotubes (SiOx-CNT) through thermal decomposition of polycarbomethylsilane adsorbed on the surface of CNTs is reported. Physical properties of SiOx-CNT samples depending on various Si contents and synthesis conditions are examined by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nitrogen isotherm, scanning electron microscope (SEM), and transmission electron microscope (TEM). Morphology of the SiOx-CNT appears to be perfectly identical to that of the pristine CNT. It is confirmed that SiOx is formed in a thin layer of approximately 1 nm thickness over the surface of CNTs. The specific surface area is significantly increased by the coating, because thin layer of SiOx is highly porous. The surface properties such as porosity and thickness of SiOx layers are found to be controlled by SiOx contents and heat treatment conditions. The preparation method in this study is to provide useful nano-hybrid composite materials with multi-functional surface properties.