Direct methanol fuel cell

A novel Sulfonated Polystyrene (PSS) has been synthesized by sulfonation polystyrene waste for a comparative study of proton exchange membranes (PEM) that is intended for fuel cell applications. The degree of sulfonation (DS) of the sulfonated PS was determined using titration method. We systematically investigated the water uptake, proton conductivity, and methanol permeability of the cross-linked membranes. The mass averaged molecular weights Mw of PSS was estimated from intrinsic viscosities measured in sulfuric acid solutions. A related homopolymer was characterized by Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy. The structures of PSS were elucidated, and the effect of sulfonation level on the PSS FT-IR spectrum was studied. PSS membrane surface morphology was investigated by SEM and AFM. The highest of proton conductivity of the membrane in the temperature range of 25-750C was found to be 3.8 µS/cm

Bimetallic PtGe and PtIn catalysts (Ge/Pt and In/Pt molar ratios ¼ 0.33, 17 wt.% Pt loading) were prepared over carbonaceous supports (carbon Vulcan, carbon nanotubes and structured mesoporous carbon). The liquid phase depositionereduction method by using 0.4 M sodium borohydride as a reducing agent was employed. The electrocatalytic activity for methanol oxidation was compared with a commercial Pt/CV E-TEK catalyst. The onset potential of the CO oxidation was shifted to less positive values for carbon Vulcan and carbon nanotubes supported catalysts and with a smaller effect in the case of mesoporous carbon supported ones. The best electrocatalytic performance was obtained by using carbon Vulcan as support of bimetallic catalysts, followed by carbon nanotubes. The performance of mesoporous carbon as a support was not adequate. PtGe/CV, PtGe/NT and PtIn/CV catalysts displayed the best performance in DMFC. The good performance of these catalysts could be due to the presence of small particle sizes with a narrow distribution, and to geometric effects (observed from different characterization techniques) related to a probable decoration of Ge or In around the small Pt particles.

Bimetallic PtGe and PtIn catalysts (Ge/Pt and In/Pt molar ratios ¼ 0.33, 17 wt.% Pt loading) were prepared over carbonaceous supports (carbon Vulcan, carbon nanotubes and structured mesoporous carbon). The liquid phase depositionereduction method by using 0.4 M sodium borohydride as a reducing agent was employed. The electrocatalytic activity for methanol oxidation was compared with a commercial Pt/CV E-TEK catalyst. The onset potential of the CO oxidation was shifted to less positive values for carbon Vulcan and carbon nanotubes supported catalysts and with a smaller effect in the case of mesoporous carbon supported ones. The best electrocatalytic performance was obtained by using carbon Vulcan as support of bimetallic catalysts, followed by carbon nanotubes. The performance of mesoporous carbon as a support was not adequate. PtGe/CV, PtGe/NT and PtIn/CV catalysts displayed the best performance in DMFC. The good performance of these catalysts could be due to the presence of small particle sizes with a narrow distribution, and to geometric effects (observed from different characterization techniques) related to a probable decoration of Ge or In around the small Pt particles.

Functionalization of CNTs by a silica layer and sulfonated groups • Improvement of proton conductivity and selectivity of the prepared composite membrane • Decreasing the methanol permeability by decreasing the size of the nanochannel • Enhancement of water uptake and ion exchange capacity by introducing the sulfonated groups Article history:

Modified polymer films with metal particles incorporated into the films by electrodeposition are known as possible electrocatalysts for various electrode reactions such as fuel cell applications. This work presents some results concerning the electrooxidation of D-glucose at modified polymer film electrodes prepared on a platinum substrate. This reaction has a great deal of interest in view of its applications to detection systems (glucose sensor), fuel cells (pacemakers) and electroorganic systhesis. The modified polymer film electrodes contain platinum and/or palladium particles dispersed in the polypyrrole film by electrodeposition in neutral media. Addition of palladium to platinum modifies the electrocatalytic behaviour of the electrode drastically. The modification is thought to involve minimisation of the poisoning of the catalyst, hence increasing its electrode activity.

This research fabricates bipolar plates for direct methanol fuel cells (DMFC) to improve compressive strength and creep behaviour. The composites comprise of poly (methyl methacrylate) (PMMA), polyurethane (PU) and carbon black (CB) those were fabricated via bulk polymerization in a casting process. The technique can create semiinterpenetrating polymer networks (IPNs) between PMMA and PU. The composites were prepared in different weight ratios PMMA/PU/CB of 75/25_5phr, 80/20_5phr and 85/15_5phr, and their quantity of IPNs in the composites are 99.27%, 97.77% and 96.71% respectively. In terms of compressive strength values, they achieve the requirement for commercial bipolar plates which are around 60 MPa, and a total creep value is approximately 0.23% at 120 minutes, 1 kPa and 80 ๐ C. The surface and volume electrical conductivity values incorporating 5 wt% of CB are 4.25x10 -7 Scm -1 and 2.05x10 -6 Scm -1 respectively. The developed composite material has a suitable combination of mechanical properties and processability for DMFC bipolar plate applications.

Direct methanol fuel cells (DMFCs) have attracted considerable scientific interest because of their ease of operation and implementation; however, poor electrocatalytic activity and durability are the main hindrances for their commercial feasibility. Moreover, the deactivation of active Pt sites, due to the coverage of CO-like species during the electrochemical oxidation reaction, significantly degrades the electrochemical surface area (ECSA). In the present work, stable Pt-supported tin-modified indium oxide (ITO) was synthesized as a promising electrocatalyst towards the methanol oxidation reaction (MOR) in DMFCs. It was found that 20 wt% Pt/ITO yielded much higher current density (~0.71 mA/cm 2 ) than the state-of-the-art carbon-supported Pt (E-TEK) electrocatalyst. Furthermore, the I f /I b ratio, which featured the CO tolerance of the electrocatalyst, of 20 wt% Pt/ITO was found to be ~1.42, which is ~1.5-fold higher than that of 20 wt% Pt/C (E-TEK). Chronoamperometry results indicated that 20 wt% Pt/ITO manifested much higher stability than 20 wt% Pt/C (E-TEK).

In the last few years, perovskite solar cells have attracted enormous interest in the photovoltaic community due to their low cost of materials, tunable band gap, excellent photovoltaic properties and easy process ability at low temperature. In this work, we fabricated hole-conductor-free carbon-based perovskite solar cells with the monolithic structure: glass/FTO/bl-TiO\(_{2}\)/(mp-TiO\(_{2}\)/mp-ZrO\(_{2}\)/mp-carbon) perovskite. The mixed 2D/3D perovskite precursor solution composed of PbI\(_{2}\), methylammonium iodide (MAI), and 5-ammoniumvaleric acid iodide (5-AVAI) was drop-casted through triple mesoporous TiO\(_{2}\)/ZrO\(_{2}\)/carbon electrode films. We found that the isopropyl alcohol (IPA) solvent vapor annealing strongly influenced on the growth of mixed 2D/3D perovskite on triple mesoscopic layers. It resulted in the better pore filling, better crystalline quality of perovskite layer, thus the improved stability and efficiency of perovskite solar cell was attributed to...

Thin-film Pd catalysts with low metal loadings (55 and 110 µg cm -2 ) were obtained by electrodeposition from a surfactant-free green electrolyte on glassy carbon (GC) electrode. Pd/GC catalysts were modified by addition of various amounts of Bi via irreversible adsorption. The catalysts were characterized by atomic force microscopy (AFM) and then studied in methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR) in alkaline solution. Electrochemical tests shown that the modification of the appropriate amount of Bi on Pd/GC catalyst enhance activity toward MOR and EOR up to about 2-3 times compared to unmodified catalysts. Besides surface Bi coverage (ƟBi) of 0.6 increase durability and provides more poisoning tolerant Pd/GC electrode in both studied reactions. The improvement of electrochemical performances of Bi modified Pd/GC catalysts is attributed to the third body effect and the bifunctional mechanism.

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Microcrystalline zirconium phosphate was exfoliated by treatment with aqueous solutions of ␣,-alkylaminoalcohols and employed for the fabrication of potato starch composite membranes. Glycerol-based and glycerol-free composite membranes, containing 5 wt% of filler, were prepared from gelatinized starch and characterized for their physico-chemical properties. Despite of a partial filler reaggregation, as revealed by XRD and SEM analysis, all the composites exhibited a significant increase in the Young's modulus with respect to the glycerol-starch membrane, up to 80% and 190% for the glycerolbased and the glycerol-free composites, respectively. For both kinds of membranes the filler delays to a large extent the starch decomposition above about 300 • C. A significant reduction in the water uptake of the composites was also observed with respect to the neat glycerol-based membrane, up to about 70% for the glycerol-free composites.

The strong drive to commercialize fuel cells for portable as well as transportation power sources has led to the tremendous growth in fundamental research aimed at elucidating the catalytic paths and kinetics that govern the electrode performance of proton exchange membrane (PEM) fuel cells. Advances in theory over the past decade coupled with the exponential increases in computational speed and memory have enabled theory to become an invaluable partner in elucidating the surface chemistry that controls different catalytic systems. Despite the significant advances in modeling vapor-phase catalytic systems, the widespread use of first principle theoretical calculations in the analysis of electrocatalytic systems has been rather limited due to the complex electrochemical environment. Herein, we describe the development and application of a first-principles-based approach termed the double reference method that can be used to simulate chemistry at an electrified interface. The simulations mimic the half-cell analysis that is currently used to evaluate electrochemical systems experimentally where the potential is set via an external potentiostat. We use this approach to simulate the potential dependence of elementary reaction energies and activation barriers for different electrocatalytic reactions important for the anode of the direct methanol fuel cell. More specifically we examine the potential-dependence for the activation of water and the oxidation of methanol and CO over model Pt and Pt alloy surfaces. The insights from these model systems are subsequently used to test alternative compositions for the development of improved catalytic materials for the anode of the direct methanol fuel cell.

We describe an approach for manipulation of biodegradable chitosan and poly(vinyl sulfonic acid) (PVS) in layer-by-layer (LBL) film adsorbed onto gold via ionic attraction. H 2 PtCl 6 was deposited onto the LBL film, with chitosan/PVS layers serving as templates to yield metallic platinum. In electrochemical experiments this LBL film exhibited electrochemical stability, low permeability to methanol and conduction/diffusion of proton to maintain the electrolytic connection. The Pt/chitosan/PVS electrode also displayed electroreduction of molecular oxygen. With these features, this Pt/chitosan/PVS film may be used between the catalyst layer and the proton exchange membrane (PEM) in direct methanol fuel cells (DMFC) and biofuel cells.

A simple numerical simulation of current flowing through electronic devices was examined for a hybrid power supply system composed of a DMFC and a capacitor connected in parallel. The simulation was investigated by representing a combination of ohmic resistance, charge transfer reaction resistance, mass transfer resistance and double layer capacitance of a DMFC as a simple ideal resistor, based on measured data when DMFC was generating electricity. The simulation result was found to agree with experimental measured current flowing through the DMFC and the capacitor, although a slight disagreement was observed because of the presence of ohmic resistance between circuit components. The simulation of DMFC-capacitor hybrid power supply system indicated the importance of the inner resistance of the capacitor. The hybrid simulation was also applied to a system assumed to consist of µDMFC and micro electrochemical capacitor (MECC) system. The effect of applying a DC-DC converter to the system was indicated. The simulation allows to predict the degree of improvement required without performing actual fabrication of µDMFC and MECC.

The long-term stability of PtCoRu/C to methanol crossover has been evaluated in a direct methanol fuel cell (DMFC) configuration. The DMFC has been subjected to continuous operation under potential step cycles. The degradation of the DMFC with PtCoRu/C has been followed by comparison of the power density curves recorded after 0, 60 and 312 h of continuous operation, and compared to that recorded for a DMFC with Pt/C. Electrochemical Impedance Spectra (EIS) were recorded directly from the DMFCs and used to identify the main degradation phenomena responsible for the loss of performance of the used fuel cell. AC impedance spectra show that the resistance of the anode reaction increases while resistance associated to the cathode reaction decreases after the long-term stability tests; however, the analysis of the power density curves unequivocally show that the performance of the DMFCs goes down during the stability tests. This apparent contradiction can be explained by taking into account the changes between the fresh and used PtCoRu/C observed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses. During the potential step cycles Ru dissolves form PtCoRu/C leading to Ptenriched catalysts which are more active for the oxygen reduction reaction (lower resistance) but less tolerant to methanol (lower power density).

The aim of this work is to identify the influence catalyst preparation methodology on the properties and the structure of metallic particles deposited over carbon nanofibers support for use in a Direct Ethanol Fuel Cell (DEFC). The catalysts were prepared by sol-gel method and a method which consists in change tin cations adsorbed in the surface, for metallic particles by a redox process.

A study of a small scale Liquid Feed Direct Methanol Fuel Cell (LFDMFC), based on solid polymer electrolyte membrane, is reported. Two ¯ow cell designs, one with a parallel ¯ow channel arrangement and the other with a spot design of ¯ow bed, are used. The structure of the DMFC comprises a composite of two porous electrocatalytic electrodes; Pt±Ru±carbon catalyst anode and Pt±carbon catalyst cathode, on either side of a solid polymer electrolyte (SPE) membrane. The performance of three Pt±Ru catalysts is compared. The in¯uence of the degree of Te¯on loading on the electrode structure is also reported. The eect of the following parameters: cell temperature, oxygen gas or air pressure, methanol liquid ¯ow rate and methanol concentration on the power performance is described.

Only few test modules (TM) are defined for the durability assessment of a PEMFC stack. The master document as well as several test modules from work package two will form the basis of the test programs in work package 3. The test modules will be validated individually, before being tested as a part of a more detailed test program, which would be application specific. The Test Programs (TP) are prepared specific to different applications. They represent topics of interest demanded by end-users concerning the function and the performance of industrial fuel cell stacks.

South Africa is undergoing a serious consideration of hydrogen economy in an effort to develop safe clean and reliable alternative energy sources for fossil fuels. Ammonia is one of the promising candidates due to its low production cost, ease in liquefaction at ambient temperatures, and high energy density as compared to methanol. Ammonia has a high content of hydrogen atoms per unit volume and can easily be cracked down into hydrogen and nitrogen. In the last four years carbon intensive coal dependent South Africa has become one of the leading global destinations for renewable energy investment. Another driving force behind the technology is the prevalence of platinum reserves found in South Africa. Platinum group metals are the key catalytic materials used in most fuel cells, and with more than 75 % of the world’s known platinum reserves found within South Africa. In this thesis, I have developed novel electrocatalysts that are highly specific and selective for production of hydr...

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A series of sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (S-PPO) and sulfonated poly(ether ether ketone) (S-PEEK) at various sulfonation degrees were prepared and characterized for their degree of sulfonation, water uptake, ion exchange capacity, proton conductivity and methanol permeability. Based on the obtained results, the optimum samples were determined and subsequently blended together at different compositions. A single glass transition temperature (T g ) was determined for all blend samples, which was attributed to the presence of sulfonate groups on polymer backbones resulting in the formation of electrostatic cross-linking besides phenyl-phenyl interactions. Moreover, the molecular level of mixing in blends was verified through WAXS patterns. According to the membrane selectivity and hydrolytic stability measurements, 75 wt.% of S-PPO and 25 wt.% of S-PEEK was selected as the optimum composition. Afterwards, different amounts of an organically modified montmorillonite (MMT) were incorporated into the predetermined optimum composition matrices to reduce the methanol permeability of the resulted nanocomposite proton exchange membranes. The XRD patterns of nanocomposites revealed the exfoliated microstructure of the clay nanolayers in the polymeric matrices. Transport property measurements of nanohybrid membranes showed that the maximum selectivity parameter of 75 wt.% S-PPO/25 wt.% S-PEEK composition appeared in the presence of 1.5 wt.% of MMT, which is 1.53 times higher than the corresponding value for Nafion ® 117. The DMFC single cell test of the optimum nanohybrids membrane at 5 M methanol feed showed an open circuit voltage of 0.77 V and maximum power density of 135 mW cm -2 in comparison with 0.67 V and 108 mW cm -2 for Nafion ® 117, respectively. Fabricated nanohybrid membranes, thanks to their high selectivity, desirable transport properties and tenability, could be considered as promising polyelectrolytes for direct methanol fuel cell applications.

Nanocomposite polyelectrolyte membranes based on phosphoric acid (H 3 PO 4 ) doped polybenzimidazoles (PBIs) with various loading weights of organically modified montmorillonite (OMMT) were prepared and characterized for direct methanol fuel cell (DMFC) applications. X-ray diffraction analysis revealed the exfoliated structure of OMMT nanolayers in the polymeric matrices. An H 3 PO 4 -PBI/OMMT membrane composed of 500 mol % doped acid and 3.0 wt % OMMT showed a membrane selectivity of approximately 109,761 in comparison with 40,500 for Nafion 117 and also a higher power density (186 mW/cm 2 ) than Nafion 117 (108 mW/cm 2 ) for a single-cell DMFC at a 5M methanol feed. V

In a direct methanol fuel cell (DMFC) with a Na"on membrane, a methanol solution fed to the anode permeates to the cathode. This phenomenon causes the depolarization loss at the cathode and the DMFC performance grows worse. In this research, by continuously measuring the concentration of CH OH, CO and CO in the exhaust gas of the cathode, the amount of methanol crossover was determined. Also, the e!ect of the thickness of polymer electrolyte membrane and the concentration of methanol solution on the amount of methanol crossover were investigated.

Micro Direct Methanol Fuel cells (mDMFC) are of considerable interest for both academic laboratories and industries to commercialize, since the energy demand has been increased. Although intensive researches are conducted to understand mDMFC, many challenges still remain to be solved to exploit them for real commercial applications. The pros and cons of various substrate materials used and various designs fabricated so far for fuel delivery are highlighted. One of the existing problems is membrane swelling, which has been reduced by the polymer modification recently. The removal of evolved CO 2 gas in the anode and reduction of water flooding in the cathode are accomplished through the advanced materials fabrication is discussed. The important parameters such as fuel, water, air and thermal managements to increase cell performance by material manipulation and design are outlined in this review. A handful of companies are trying mDMFC technology toward real commercial strides. We have also presented an update of the achievements so far by these companies.

Emergence of nanotechnology has resulted in the introduction of the electrospinning process in fabricating and characterising the polymer electrolyte membrane from the sulfonated poly (ether ether ketone) (SPEEK) nanocomposite membrane comprised of electrospun Cloisite15A® (e-spun CL) for direct methanol fuel cell (DMFC). Poly (ether ether ketone) polymer is sulfonated up to 63% by sulfuric acid. SPEEK63/e-spun CL nanofbers were fabricated via electrospinning in which SPEEK63 was used as carrier polymer while the SPEEK63/e-spun CL nanocomposite membrane was obtained by the casting method. Characterizations on physical, morphological and thermal properties of SPEEK63/e-spun CL were conducted and compared to the SPEEK membrane fabricated by casting simple mixing 2.5wt.% Cloisite15A® and 5.0wt.% triaminopyrimidine solution (SPEEK63/2.5CL/5.0TAP). Scanning electron microscopy (SEM) showed well electrospun Cloisite15A® with an average diameter nanofber around 187.4 nm. Moreover, feld emi...

Void-free electrospun SPEEK/Cloisite15A ® densed (SP/e-spunCL) membranes are prepared. Different loadings of Cloisite15A ® (0.10, 0.15, 0.20, 0.25 and 0.30 wt %) are incorporated into electrospun fibers. The physico-chemical characteristics (methanol permeability, water uptake and proton conductivity) of the membranes are observed. Thermal stability of all membranes is observed using Thermal Gravimetry Analysis (TGA). The thrree stages of degradation range between 163.1 and 613.1 • C. Differential Scanning Calorimetry (DSC) is used to study the wettability of the membranes. SP/e-spunCL15 shows the lowest freezing bound water of 15.27%, which contributed to the lowest methanol permeability. The non-freezing bound water that proportionally increased with proton conductivity of SP/e-spunCL15 membrane is the highest, 10.60%. It is suggested that the electrospinning as the fabricating method has successfully exfoliated the Cloisite in the membrane surface structure, contributing to the decrease of methanol permeability, while the retained water has led to the enhancement of proton conductivity. This new fabrication method of SP/e-spunCL membrane is said to be a desirable polymer electrolyte membrane for future application in direct methanol fuel cell field.

One of the main problems in direct methanol fuel cell (DMFC) application is methanol crossover. In order to solve the problem, an exfoliated void-free electrospun Sulfonated Poly(Ether Ether Ketone) (SPEEK)/cloisite nanocomposite membrane was developed. The membrane was prepared by immersing electrospun SPEEK/cloisite fiber mats onto incomplete solidified SPEEK polymer matrix. A well dispersed and reduction size of cloisite particles that ranges from 0.29–0.39 µm was observed by using Scanning Electron Microscopy Analysis (SEM) and Atomic Force Microscope (AFM). The effect of the morphology of the composite membrane in terms of degree of dispersion state of the Cloisite on the membrane performance was discussed. SP/e-spunCL15 with fully exfoliated structure exhibited the highest performance as compared to other tested membranes and Nafion® 115 with current density of 1042.2 mAcm−2 and power density of 1.18 mWcm−2. Improved morphological, dimensional change properties, and performanc...

Response surface methodology (RSM) was utilized to design the experiments at the settings of solution concentration, voltage and the collector distance. It also imparted the evaluation of the significance of each parameter on the resultant physico chemicals (proton conductivity, methanol permeability and water uptake). The investigations were carried out in the two-variable process domains of several collector distances as applied voltage and the solution concentration were varied at a fixed polymer molecular weight. The result showed that all three factors were found statistically significant in the production of void free electrospun SPEEK/Cloisite membrane. All responses were correlated to these variables by using a second order polynomial function. The optimum condition for void free electrospun SPEEK/cloisite was at 0.17 wt% concentration with applied voltage of 22.15 kV and 18.83 cm distance from needle tip to screen collector.

A coherent review on the advanced Proton exchange membranes (PEMs) for direct methanol fuel cell (DMFC) application and the future direction in the development of a high performance polymeric membrane for DMFC were discussed in this paper. PEMs have a profound influence on performance of DMFC. The PEMs are categorized into five groups which are partially fluorinated, perfluorinated ionomers, acid-base complexes, non-fluorinated ionomers, hydro carbon and aromatic polymers. Many researchers have investigated the functionalization methods on the PEMs to solve methanol crossover problem while obtaining low electronic conductivity, high proton conductivity, low electro osmotic drag coefficient, high mechanical properties and good chemical and thermal stability. Including in this review, fabrication of PEM using electrospinning process coupled with the promising functionalized polymeric materials which were known to be the most important initiatives at present in order to further expand the full potential of DMFC performance.

An enzyme electrode is prepared with a composite coating on an electrical conductor. The composite coating is formed from a casting solution of a perfluorosulfonic acid polymer, an enzyme, and a carbon supported catalyst. The solution may be cast directly on the conductor surface or may be formed as a membrane and applied to the surface. The perfluorosulfonic acid ionomer

A method of fuel circulation with a fixed amount of fuel was employed to investigate a direct methanol fuel cell (DMFC) stack that was built with metal foam flow fields for the air and fuel flows. The stack power output increases significantly with environmental temperature from 20 to 40 • C. The average peak power per cell at 40 • C is 26 mW cm -2 per cell. The average discharge voltage per cell at peak power does not change with temperature but remains at 0.3 V. The energy output of the stack was determined at constant current or constant voltage with a fixed amount of methanol to feed the anode of the stack until the fuel was consumed. The results by constant current discharge show that at higher temperature the stack has remarkably higher energy output; while at the same temperature only a suitable magnitude of discharge current can achieve the highest energy output. The results by constant voltage discharge show that the Faradic efficiency is 86%, and the energy efficiency is 17% at 30 • C.

In this paper, a membrane electrode assembly (MEA) that uses a stainless steel fiber felt (SSFF) to replace the anode current collector and backing layer is designed and fabricated for a micro-direct methanol fuel cell (DMFC). At the same time, a conventional MEA with carbon paper (CP) as the support layer of the anode gas diffusion layer was fabricated as a contrast experiment. To study the effect of the novel structure on the anode or cathode electrode process, a reference electrode was built inside a single cell. The results show that the novel MEA has a smaller cathode polarization by reducing the methanol crossover and provides a smaller anode polarization by improving the methanol transportation.

In this paper, a systemic model based on the equivalent circuit modeling method is developed in order to analyze the electrical behavior of direct methanol fuel cell (DMFC) stack in complex systems. The systemic model consists of the polarization curve subsystem, the long time discharge subsystem, and the temperature distribution of catalyst layer subsystem. The effect of various operating parameters on the behavior of the DMFC stack is evaluated by the systemic model. In addition, the systemic model is applied to design a DMFC stack with 4 single DMFCs connected in series. The simulated current-power profiles and time-power profiles are validated by the experimental results of the designed DMFC stack. Numerical results such as the effect of assembly pressure and the temperature distribution of catalyst layer are also discussed. Based on the numerical results, the most appropriate assembly pressure for the DMFC stack is 1.5 MPa. The total energy released at the current of 400 mA is the maximum according to both the simulated and experimental results. This systemic model provides a meaningful method to design DMFC stacks in the view of the system-level.

In this paper, a systemic model based on the equivalent circuit modeling method is developed in order to analyze the electrical behavior of direct methanol fuel cell (DMFC) stack in complex systems. The systemic model consists of the polarization curve subsystem, the long time discharge subsystem, and the temperature distribution of catalyst layer subsystem. The effect of various operating parameters on the behavior of the DMFC stack is evaluated by the systemic model. In addition, the systemic model is applied to design a DMFC stack with 4 single DMFCs connected in series. The simulated current-power profiles and time-power profiles are validated by the experimental results of the designed DMFC stack. Numerical results such as the effect of assembly pressure and the temperature distribution of catalyst layer are also discussed. Based on the numerical results, the most appropriate assembly pressure for the DMFC stack is 1.5 MPa. The total energy released at the current of 400 mA is the maximum according to both the simulated and experimental results. This systemic model provides a meaningful method to design DMFC stacks in the view of the system-level.

In this paper, a membrane electrode assembly (MEA) that uses a stainless steel fiber felt (SSFF) to replace the anode current collector and backing layer is designed and fabricated for a micro-direct methanol fuel cell (DMFC). At the same time, a conventional MEA with carbon paper (CP) as the support layer of the anode gas diffusion layer was fabricated as a contrast experiment. To study the effect of the novel structure on the anode or cathode electrode process, a reference electrode was built inside a single cell. The results show that the novel MEA has a smaller cathode polarization by reducing the methanol crossover and provides a smaller anode polarization by improving the methanol transportation.

Two-dimensional hexagonal arrays of interconnected Co 3 O 4 nano-rods or disconnected monodimensional Co 3 O 4 nano-rods were nano-cast fabricated using SBA-15 as hard template with or without intra-wall microporosity, respectively. A clean, efficient and facile high temperature steam posttreatment is proposed to control the microporosity and the interconnectivity of the nanocasted oxide phase. Characterization by small-angle X-ray diffraction (XRD), nitrogen adsorption, scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) suggests that the selective removal of micropores is resulted from hydrothermal restructuring within the pore wall of calcined SBA-15 followed by a sequential process, including hydrolysis and re-condensation of internal surface siloxane bonds and dissolution-migration-deposition of amorphous debris external onto the SBA-15 under the atmosphere of pure water vapor.

A major challenge in direct methanol fuel cells is the crossover of methanol, from the anode to the cathode. The flowing electrolyte (FE) concept is one potential method to reduce or eliminate the effects of this problem, and the corresponding fuel cell is known as a flowing electrolyte e direct methanol fuel cell (FE-DMFC). In this study, the effect that the cathode flow field has on the performance of the FE-DMFC was investigated in a COMSOL Multiphysics environment. Methanol concentration, oxygen concentration, pressure distribution and velocity distributions were simulated for a single serpentine, parallel serpentine, triple serpentine and a grid type flow field configuration. The results of this study demonstrate the importance of the velocity distribution on the oxygen transport and its impact on the fuel cell's performance. As such, of the tested flow fields, the grid flow field obtained the lowest performance due the formation of locally low concentration zones (or dead zones) causing an increase in the cathode's concentration polarization. The single serpentine flow field on the other hand provided the best performance due to the better reactant coverage over the CCL.

< Sulfonated polysulfone was used as ionomer in a DMFC anode at 130 C < The sPSU based anode has a high activity for the methanol oxidation. < The anode has a good mechanical stability and adhesion on the Nafion Ò membrane. < Anode catalyst inks based on sPSU do not require toxic and flammable solvents.

The carbon nanotube (CNT) synthesised by the template carbonisation of polypyrrole on alumina membrane has been used as the support for Pt-WO 3 , Pt-Ru, and Pt. These materials have been used as the electrodes for methanol oxidation in acid medium in comparison with E-TEK 20 wt% Pt and Pt -Ru on Vulcan XC72R carbon. The higher electrochemical surface of the carbon nanotube (as evaluated by cyclic voltammetry) has been effectively used to disperse the catalytic particles. The morphology of the supported and unsupported CNT has been characterised by scanning electron micrograph and high-resolution transmission electron micrograph. The particle size of Pt, Pt -Ru, and Pt -WO 3 loaded CNT was found to be 1.2, 2, and 5 nm, respectively. The X-ray photoelectron spectra indicated that Pt and Ru are in the metallic state and W is in the þVI oxidation state. The electrochemical activity of the methanol oxidation electrode has been evaluated using cyclic voltammetry. The activity and stability (evaluated from chronoamperometric response) of the electrodes for methanol oxidation follows the order: GC/CNT -Pt-WO 3 -Nafion . GC/E-TEK 20% Pt -Ru/Vulcan Carbon -Nafion . GC/CNT -Pt-Nafion . GC/E-TEK 20% Pt/Vulcan carbon-Nafion . Bulk Pt. The amount of nitrogen in the CNT plays an important role as observed by the increase in activity and stability of methanol oxidation with N 2 content, probably due to the hydrophilic nature of the CNT.