bluuebunny/crossref_metadata_2025 huggingface dataset:
In Situ Measurement of Oxygen Permeability in Polymer Electrolyte Membranes
Authors: Sambandam Satheesh , Ramani Vijay
Published: September 2009

Oxygen permeability in polymers (Nafion® and Sulfonated polyether ether ketone or SPEEK) was measured in-situ using a cylindrical Pt microelectrode by chronoamperometry at conditions mimicking actual fuel cell operation. The micro electrode (working electrode) reduces instantaneously any oxygen permeating through the polymer by changing to a potential at which oxygen transport is limited by diffusion. From the current profile corresponding to the potential hold, diffusivity and concentration of oxygen in the polymer was estimated. Durability of fuel cell membrane has been a long standing issue in fuel cell commercialization. Two modes of membrane decay widely reported in the literature are formation of (i) H2O2 and its subsequent decomposition to yield radicals and (ii) O2 reduction reaction intermediates. Viability of the use of Pt microelectrode in detection of H2O2 in both liquid and solid electrolytes was also studied. In both cases H2O2 was forcibly added to the system.
The Role of Fe in the Preparation of Carbon Alloy Cathode Catalysts
Authors: Nabae Yuta , Malon Michal , Lyth Stephen M. , Moriya Shogo , Matsubayashi Katsuyuki , Islam Nazrul , Kuroki Shigeki , Kakimoto Masa-aki , Ozaki Jun-ichi , Miyata Seizo
Published: September 2009

Pyrolysis of iron phthalocyanine/phenolic resin (FePc/PhRs) and phthtalocyanine/phenolic resin (Pc/PhRs) was studied to clarify the effect of Fe during the preparation of carbon alloy cathode catalysts. FePc/PhRs pyrolyzed at 600° showed the best electrocatalytic activity for oxygen reduction. CHN elemental analysis suggests that the catalysts with higher nitrogen content tend to show better catalytic activities. The results of TG/DTA/MS and IR suggest that Fe increases the nitrogen content of the catalysts by enhancing the interaction of phthalocyanine moiety and phenolic resin.
Temperature Measurement in Through-plane Direction in PEFC with a Fabricated In-line Thermocouple and Supporter
Authors: Lee Sang-Kun , Ito Kohei , Sasaki Kazunari
Published: September 2009

Temperature distribution in the through-plane direction in polymer electrolyte fuel cell (PEFC) is key information to achieve proper water management. We fabricated an in-line thermocouple of 49 μm diameter, insulated by Parylene coating with 12 μm thickness. The supporter for the thermocouple was fabricated to position the thermocouple to an exact measurement-point in cell, and to protect the thermocouples from the damage during assembling and operating the cell. Seven in-line thermocouples were placed in the cell in array. It was found that the insertion of thermocouples did not cause large decrease of the cell performance. When the current of 0.3 A/cm2 was loaded under the condition of 60 {degree sign}C separator temperature with supplying H2/Air humidified at 80 % RH, the cathode catalyst layer temperature showed the increase of 1.9 {degree sign}C and the maximum in the cell.
High Resolution Neutron Imaging of Water in the Polymer Electrolyte Fuel Cell Membrane
Authors: Mukherjee Partha P. , Mukundan Rangachary , Spendelow Jacob S. , Davey John R. , Borup Rodney , Hussey Daniel S. , Jacobson David L. , Arif Muhammad
Published: September 2009

Water transport in the ionomeric membrane, typically Nafion®, has profound influence on the performance of the polymer electrolyte fuel cell, in terms of internal resistance and overall water balance. In this work, high resolution neutron imaging of the Nafion® membrane is presented in order to measure water content and through-plane gradients in situ under disparate temperature and humidification conditions.
Visualization of Liquid Water Distribution in an Operational PEMFC by Soft X-Ray Radiography
Authors: Sasabe Takashi , Tsushima Shohji , Hirai Shuichiro , Minami Katsunori , Yada Keiji
Published: September 2009

Liquid water distribution in the operational Proton Exchange Membrane Fuel Cell (PEMFC) was visualized by soft X-ray radiography. To achieve a maximum sensitivity towards liquid water, low electron beam energy in soft X-ray range was chosen. As a result, the spatial resolution of 0.8 um and temporal resolution of 2 sec were obtained. In addition, in-plane and through-plane observation of operational cell was carried out and correlation between the accumulation of liquid water and the gas flow rate was observed. At high gas flow rate condition, liquid water accumulation was only observed in the interface between the catalyst layer and the gas diffusion layer (GDL). With decrease of gas flow rate, the liquid water content within the GDL increased and erupt of the liquid water to the channel was observed.
An Investigation of Thermally-Induced Water Transport in Polymer Electrolyte Fuel Cells with Neutron Radiography Imaging Technique
Authors: Fu Richard S. , Preston Joshua S. , Pasaogullari Ugur , Tabuchi Yuichiro , Shiomi Takeshi , Hussey Daniel S. , Jacobson David L.
Published: September 2009

A fundamental experimental study of the reported water transport across the PEM under a temperature gradient is sought. We wish to experimentally verify the water transport phenomenon observed with neutron radiography and numerical modeling. The experimental observations show a presence of water content gradient across the PEM, indicating water flux in the direction from the high temperature side to the low temperature side, when sufficiently humidified. Higher water content by the PEM is seen at a larger thermal gradient when sufficiently humidified. The numerical results predict the order of magnitude of water transport; however, more accurate material characterization is needed for improvement.
Stability of Pt Alloy High Surface Area Catalysts
Authors: Hartl Katrin G. , Mayrhofer Karl J. , Arenz Matthias
Published: September 2009

Alloys of Pt with other transition metals are a promising class of fuel cell cathode catalysts. In the present work it is shown that the surface composition of high surface area Pt3Co electrocatalysts can be changed in situ by means of different electrochemical treatments. Surface segregation is detected by cyclic voltammetry in base electrolyte where the Pt alloy is stable and specific peaks reflect the surface composition. During CO annealing Pt surface segregation takes place and Co atoms disappear from the surface. Contrary, by cycling in Ar saturated solution to high potentials the inverse process takes place and Co atoms re-emerge on the surface, an effect of high importance considering the stability of alloy electrocatalysts in acidic PEM fuel cells.
Oxygen Evolution Co-Catalysts at Fuel Cell Cathodes for Degradation Mitigation during Simulated Start-up Shut-down Cycles
Authors: Srivastava Ratndeep , Strasser Peter
Published: September 2009

We herein report a methodology which uses an oxygen evolution reaction (OER) co-catalyst, such as Ru and RuO2 together with a highly active ORR catalyst. The co-catalyst is applied in the cathode layer with loadings of 0.035 - 0.04 mgRu/cm2 and is uniformly mixed with the ORR catalyst prior to electrode preparation. Oxygen evolution catalysts (OER) like Ru/C and RuO2/C mixed with ORR catalysts enhance the oxidation of water/OH- to oxygen and therefore provide significant protection of other redox active species at high cathode potentials Our measurements indicate that loss in ECSA, carbon support and activity for ORR catalyst combined with OER was significantly reduced as compared to an unprotected catalyst layer.
Oxide Formation and Removal on Pt Surfaces Under Potential Cycled Conditions
Authors: Holby Edward F. , Shao-Horn Yang , Sheng Wenchao , Morgan Dane
Published: September 2009

Surface oxides on Pt play a central role in the catalytic activity and durability of Pt nanostructures, especially under potential cycling conditions. This work constructs a model for the oxide formation and removal portion of Pt cyclic voltammograms based on underlying system thermodynamics and kinetics. Limitations of the model show the need to accurately include the roles of place exchange and surface oxide phases in order to quantitatively match experimental data. However, a better understanding of surface oxidation mechanisms is still required for quantitative modeling.
Nanoparticle Size Effects on the Electrochemical Dissolution Rate of Pt
Authors: Goeke Ronald S. , Datye Abhaya K. , Atanassov Plamen , St-Pierre Jean
Published: September 2009

Model Pt catalysts have been fabricated directly on planar glassy carbon supports by physical vapor deposition. Potential application of these catalysts toward the understanding of fuel cell catalyst deactivation is demonstrated. The dissolution rate of the Pt is a key step to many of the deactivation processes which can be easily measured on these model systems. A decrease in the equilibrium potential for platinum oxidation on nanometer sized particles is shown. These catalysts are characterized by scanning electron microscopy and rotating disk electrode experiments. Development of a templated synthesis route to create Pt nanoparticle arrays of controlled size and spacing is demonstrated.
Carbon-supported Ir-Ti as a Novel Cathode Catalyst for PEFCs
Authors: Li Bing , Qiao Jinli , Yang Daijun , Lv Hong , Ma Jianxin
Published: September 2009

Carbon-supported Ir and Ir-Ti nanoparticle catalysts were successfully synthesized using IrCl3 and TiCl3 as the Ir and Ti precursors in ethylene glycol refluxing at 120oC. These nanoparticles were evaluated as cathode catalysts in proton exchange membrane fuel cell (PEMFC). The catalysts were characterized by X-ray diffraction (XRD) and high resolution transmission electron microscope (TEM). Experiments showed that the carbon-supported 40%Ir-10%Ti/C catalysts give a well dispersion with mean particle size of 2 nm. The electrochemical characterizations, performed using a rotating disk electrode by cyclic voltammetry with emphasis on the activity of the catalysts, are presented in 0.5 M H2SO4. The 40%Ir-10%Ti/C exhibits promising catalytic performance in terms of oxygen reduction reaction (ORR). High cell performance was achieved with a loading of 0.4 mg cm−2 40%Ir-10%Ti/C catalyst, which results in a maximum a power density of 459 mW cm−2.
RRDE Measurements of ORR Activity of Pt1-xIrx (0 < x < 0.3) on High Surface Area NSTF-coated GC Disks
Authors: Liu Gary C. , Sanderson Robbie , Verndstorm George , Stevens David , Atanasoski Radoslav , Debe Mark , Dahn Jeff R.
Published: September 2009

Layered Pt1-xIrx (0 < x < 0.3) and Pt films were sputtered onto mirror-polished and nano-structured thin film (NSTF)-coated GC disks. Rotating ring disk electrode studies of oxygen reduction reaction activity (ORR) were completed for all disks prepared. The NSTF-supported catalysts had much higher active surface area and reached the diffusion-limited current at a higher potential than the mirror-polished supported catalysts. The surface enhancement factor (SEF) of Pt on NSTF-coated disks was approximately 14. The SEF increased, (reaching a maximum of 22 at x = 0.2 in Pt1-xIrx) as the Ir content increased. The kinetic ORR current density also increased with increasing Ir content. A similar trend was not observed for catalyst coated, mirror-polished disks. All of the catalyst/support combinations had identical Tafel slopes and area specific current densities suggesting that the Pt is the active catalytic ingredient.
Pulse Voltammetry Investigations of Platinum Metal Fuel Cell Electrodes
Authors: Pietrasz Patrick , Zawodzinski Thomas A.
Published: September 2009

Pulse voltammetry as a technique was used to explore the conditions under which platinum oxides form in an operating fuel cell. The technique is shown to have high sensitivity towards adsorbed surface species, and is useful for the realization of pulse type in situ fuel cell experiments.
PEMFC performance of MEAs Based on Perfluorinated Nanocomposite Membranes Modified by Polyaniline
Authors: Vicente Compañ-Moreno , Molla Sergio , Sytcheva Ana , Berezina Ninel , Suarez Karina , Solorza Omar , Riande Evaristo
Published: September 2009

This work summarizes results on the modification of perfluorinated sulfocationic membranes MF-4SC by polymerization in situ of aniline. The investigation of the transport properties of polyaniline/MF-4SC composites membranes after different times of polymerization has been analyzed. After 3 hours of aniline polymerizacion, both pristine and composite membranes exhibit higher protonic conductivity. The performance of fuel cells containing MEAs from MF-4SC and polyaniline/MF-4SC was studied and the kinetic parameters governing the voltage dependence on current density estimated.
On the Influence of Sulphur on the Pyrolysis Process of FeTMPP-Cl-based Electro-Catalysts with Respect to Oxygen Reduction Reaction (ORR) in Acidic Media
Authors: Kramm Ulrike I. , Herrmann Iris , Fiechter Sebastian , Zehl Gerald , Zizak Ivo , Abs-Wurmbach Irmgard , Radnik Jörg , Dorbandt Iris , Bogdanoff Peter
Published: September 2009

Pyrolysis of chloroiron-tetramethoxyphenyl-porphyrin (FeTMPP-Cl) in the presence of iron oxalate ({plus minus} sulphur) leads to the formation of higly porous and active catalysts for the oxygen reduction reaction (ORR). In order to clarify the influence of sulphur the pyrolysis process is analyzed by thermogravimetry (TG) and by high-temperature X-ray diffraction (HT-XRD). In the absence of sulphur iron carbide (FexC) is formed which catalyses the proceeding graphitisation of the pyrolysis products. As a result catalytic active centres are decomposed by this reaction. This can be avoided by the addition of sulphur because iron monosulphide (FeS; troilite) is formed instead of FexC. Furthermore, FeS can easily be removed in a successive etching step so that nearly all inactive by-products can be removed. The results are in accordance with the higher electrochemical performance of the sulphur containing catalysts.
The pH Dependence of the Oxidation Reaction of SO2 at a Platinum Electrode Studied by Voltammetric and In Situ Infrared Spectroscopic Measurements
Authors: Iwasaki Chihiro , Ohsaka Takeo , Kitamura Fusao
Published: September 2009

The electrooxidation of S(IV)-contained species in the aqueous solution of sodium sulfite at a polycrystalline Pt electrode was studied by cyclic voltammetry and in situ infrared spectroscopy as a function of solution pH (1{less than or equal to}pH{less than or equal to}5). The diffusion-controlled anodic current observed at >0.7 V vs. Ag | AgCl | KCl sat. decreased in the solution of pH larger than 2, and reached a minimum value at pH 5. On the other hand, the activation effect by pre-polarization of the Pt electrode was observed in all of the pH solutions investigated. In situ infrared spectroscopic measurements undertaken during the oxidation reaction indicated that the main oxidation products were S(VI) species assignable either to HSO4¯ or SO4 2−.
Proton Exchange Membrane Fuel Cell Stack with Interleaved Boost Converter for Vehicular Applications
Authors: Gudipati Harshitha
Published: September 2009

A fuel cell is a clean and green way of generating electricity from the chemical energy. Especially when used in vehicles, it will be used to curb the vehicular pollution. This paper discusses the modeling of a proton exchange membrane fuel cell when used in transportation applications. To reduce the cost of testing, a simulation was done in MICROSIM PSPICE by modeling a fuel cell that generates 100 KW of power at a constant voltage of 300 V. Generally, the output of fuel cell will be coupled to a boost converter that regulates the output voltage to the required level. A boost converter however can inject current harmonics into the fuel cell which might otherwise damage the durability of fuel cell. Therefore an interleaved boost converter was investigated to reduce current harmonics. With an interleaved boost converter, the current harmonics on fuel cells can be reduced and the output voltage levels can be increased. Further recommendations of the circuit have also been suggested that could lead to development of an efficient and an economical fuel cell vehicle.
Electrochemical Micro-Reactor for the Determination of Intermediate Products in Fuel Cell Reactions
Authors: Meier Jan O. , Cremers Carsten , Tübke Jens
Published: September 2009

In this document, a newly designed electrochemical plug flow reactor system is presented. For a first preliminary test, ethanol in sulfuric acid was oxidized at a platinized titanium mesh electrode as working electrode of the reactor. Qualitative concentration behaviors were measured with mass spectrometric methods. A first result is that the reactor, in this configuration, seems to work properly.
Development of PEFC Electrode for Stable Running Under High Temperature and Low Humidity Condition
Authors: Nishiguchi Hiroto , Fukumoto Hisatoshi , Yoshioka Shoji , Matsumoto Shuichi
Published: September 2009

To prepare a high water-holding cathode catalyst layer with good polymer electrolyte fuel cell performance under low humidity conditions, the quantity of water contained in the cathode catalyst layer and behavior of the water detachment were tested by estimating the weight change by thermogravimetry analysis. The results revealed that cell performance under low humidity conditions particularly depended on the water-holding ability of the contained ionomer in the catalyst layer.
Impedance and Polarization Analysis of Cathode and Anode Performance in a Working Direct Methanol Fuel Cell
Authors: Lim Pau-Yee , Wang C.H. , Chen S.Wen , Chang S C , Tsai Li-Tuan , Peng Alex , Wang C P
Published: September 2009

A comprehensive and systematic DMFC MEA performance evaluation was conducted based on the effect of the parameter of the major constituent of MEA, such as microporous layer (MPL) and proton exchange membrane. The MEA under fuel cell operating condition have been characterized for electrochemical polarization and impedance spectroscopy of its anode and cathode, simply using a unique single cell stack measurement setup consisting of an Ag/AgCl reference electrode. The anode and cathode polarization curves allow separating the anode and cathode contribution to the overall performance of the DMFC MEA. Electrochemical impedance spectroscopy (EIS) analysis further demonstrates the contribution of each component of the anode and cathode to the cell performance
Accelerated Degradation of Perfluorinated Sulfonic Acid Membranes
Authors: Carlsson Anna H. , Joerissen Ludwig
Published: September 2009

The degradation of PFSA membranes in fuel cells is a critical factor for fuel cell life time. Ex situ methods for determining the degradation processes have been used extensively, mainly radically initiated from gas or liquid phase. Gas phase degradation has proven to cause cleavage of the main polymer chain causing the degradation speed to increase. In this study decomposition products washed out in the water form both gas and liquid phase degradation experiments have been analyzed. Decomposition products were pre-concentrated using solid phase extraction (SPE) and analyzed with HPLC-MS. The distribution of decomposition products is significantly different for gas phase and liquid phase degradation. The same analysis procedure is applied on water condensed during fuel cell operation. The HPLC-MS chromatogram showed that the condition inside a fuel cell operating at optimal conditions, most probably is less harsh than those in both liquid and gas phase ex situ degradation experiments.
Effect of the Operation and Humidification Temperatures on the Performance of a PEM Fuel Cell Stack
Authors: Pérez-Page Maria , Pérez-Herranz Valentin
Published: September 2009

Proton exchange membrane (PEM) fuel cells have attracted grate attention in recent years as a promising replacement for traditional engines. The performance of PEM fuel cells is known to be influenced by many parameters such as operation temperature and humidification of the gas streams. In this work, a testbench was developed to monitor and control a 300W fuel cell stack. Series of polarization curves with different fuel cell operation temperatures and humidification temperatures have been studied. From the polarization curves the values of kinetic parameters such as the Tafel slope and the cell resistance have been calculated with the fit of the experimental data to an empirical model. The effect of the fuel cell and humidification temperatures on the kinetic parameters has been studied
High Temperature Operation of Direct Ethanol Fuel Cells with Nafion-TiO2 Membranes and PtSn/C Electrocatalysts
Authors: Isidoro Roberta , Matos Bruno , Dresch Mauro , Spinacé Estevam , Linardi Marcelo , Traversa Enrico , Fonseca Fabio C. , Santiago Elisabete I.
Published: September 2009

In this study, both PtSn/C electrocatalysts and composites electrolytes based on Nafion and mesoporous titania (Nafion-TiO2) were evaluated in direct ethanol fuel cell operating at 130oC. PtSn/C catalysts with different compositions were prepared by alcohol-reduction process. The electrochemical activity of these electrocatalysts was verified by cyclic voltammetry and chronoamperometry measurements. Cast Nafion-TiO2 composites were characterized by differential scanning calorimetry and ac impedance spectroscopy. The water uptake of the composites was determined by gravimetry. Membrane electrode assemblies composed by Nafion-TiO2 electrolyte and PtSn/C anode were evaluate in DEFC operating in 80-130oC temperature range. Polarization curves showed an enhanced performance (maximum power density of ~50 mW cm-2) for DEFC using combined PtSn/C (60:40) electrocatalyst and Nafion-TiO2 (10 wt%) operating at 130oC.
A DFT Study for the Durability of Perfluorosulfonic Acid Membrane
Authors: Tokumasu Takashi , Ogawa Izumi , Koyama Michihisa , Ishimoto Takayoshi , Miyamoto Akira
Published: September 2009

Durability of perfluorosulfonic acid (PFSA) membrane is an important factor to improve the lifetime of PEFC. In this study the bond dissociation energy of PFSA molecule was investigated by quantum chemistry method to provide basic information for designing more durable PFSA membrane. Nafion® was used as a PFSA molecule. All calculations were performed by DMol3. Chemical bond strengths of PFSA molecule were analyzed exhaustively. The vulnerable bond was identified by comparing the results. The same calculations were performed for ionized PFSA molecule to find out the influence of the ionization state on the bond strength. Moreover, the possibility for improving durability of PFSA membrane was investigated by substituting H atoms or CH3 groups for a part of F atoms.
Microscopic Observation of Freezing Phenomena in PEM Fuel Cell at Cold Start
Authors: Saito Masataka , Tabe Yutaka , Chikahisa Takemi
Published: September 2009

In Polymer electrolyte membrane fuel cells (PEMFCs), the freezing of produced water induces the extreme deterioration of cell performance below zero. This phenomenon is serious problem in cold regions and is needed to be solved to achieve the practical use of PEMFC. In this study, we investigate ice distribution in the catalyst layer (CL) and in the gas diffusion layer (GDL) to clarify the freezing mechanism using an optical microscope and a CRYO-SEM. The observation result shows that the cold start at -10{degree sign}C makes ice at the interface between the CL and the micro porous layer of GDL. Little ice is, however, observed in the cold start at -20{degree sign}C, which indicates the ice formation in the CL. The CRYO-SEM observation is conducted at -20{degree sign}C to investigate the ice formation in the CL, and the result shows that this method is useful to clarify the ice distribution and the freezing mechanism.
Key Issues to the Preparation of Methanol-tolerant Cathode Catalyst for DMFC
Authors: Chen Ying-Chieh , Chen Wun-Liang , Lo Man-Yin , Chen Yen-Ze , Feng Er-Kuo , Chen Y. W. , Liu Tuan-Chi
Published: September 2009

Platinum is by far the best catalyst for the cathodic oxygen reduction reaction (ORR) in DMFC. However, the performance of Pt only catalyst has not reached a status set forth for the commercialization of DMFC. The most serious problem to the cathode catalyst is mainly caused by the methanol crossover from the anode through the membrane. Methanol undergoes oxidation reaction at the cathode because Pt is one of the most active methanol oxidation catalysts. Mixed-potential due to cathodic methanol oxidation is detrimental to the performance of the cathode catalyst. Furthermore, incomplete oxidation of methanol also resulted in the accumulation of CO on the Pt surface. This CO poisoning effect greatly reduces the availability of Pt active site needed for the cathodic ORR. Active and methanol tolerant cathode catalyst is desperately needed to combat the adverse effect brought along by crossover methanol. The objective of this paper is to investigate the key issues for the preparation of catalyst with both high ORR activity and methanol tolerance.
Theoretical Study on Dissoloved Structure of Pt Complex in Polymer Electrolyte Fuel Cell
Authors: Ishimoto Takayoshi , Nagumo Ryo , Ogura Teppei , Koyama Michihisa
Published: September 2009

We theoretically analyzed the formation energy and solvation free energy of four- and six-coordinated Pt(II) and Pt(IV) complexes with three types of ligands (H2O, OH-, and CF3SO3-) as a model of dissolved Pt species to understand the Pt electrocatalyst degradation and dissolution mechanisms. All calculations were performed under the generalized gradient approximation (GGA) with Becke-88 exchange and Lee-Yang-Parr correlation functionals (BLYP). Solvent effects in water were estimated using the conductor-like-screening model (COSMO). The calculated results clarified that Pt(IV) complexes are more energetically favorable than Pt(II) complexes, indicating that the Pt(IV) complexes are more probable as dissolved species than Pt(II) complexes. We also analyzed the geometrical parameters (Pt...O) and atomic charge of O in ligands. These local relaxations about geometry and atomic charge are one of the factors to determine the stability of dissolved Pt species.
Raman Investigation of Degradation and Ageing Effects in Fuel Cell Membranes
Authors: Holber Mikael , Carlsson Anna H. , Johansson Patrik , Jörissen Ludvig , Jacobsson Per
Published: September 2009

Increased life-time of the proton conducting membrane of polymer electrolyte membrane fuel cells is the key to improve the endurance of fuel cell stacks. Here we present a Raman spectroscopy investigation of a fully fluorinated sulfonated membrane from a 1500h FC steady-state experiment compared with Nafion® membranes aged in hydrogen peroxide and Fenton's solution. The latter approach as an attempt to develop a screening method based on accelerated ageing. In all membranes degradation is evident. The Raman results of the fuel cell tested membrane demonstrate a loss of functional sulfonic acid groups throughout the membrane. The accelerated ageing, on the other hand, results in degradation readily observed: e.g. loss of polymer material, opaque areas, and brittleness. Notably, the relative concentration of functional sulfonic groups stays constant, indicating that the accelerated ageing methods primarily attack the backbone of the membrane.
Effect of Air Contaminants on the Electrolyte Degradation in Polymer Electrolyte Membrane Fuel Cells
Authors: Imamura Daichi , Yamaguchi Eriko
Published: September 2009

The effect of air contaminants (NH3, NO2, H2S, and SO2) on electrolyte degradation was evaluated in PEMFCs. 2 ppm of these contaminants were supplied, and the F− release rate in the cathode effluent water was analyzed under a current density of 1000 mA/cm2 at 80 {degree sign}C. In the case of sulfur species H2S and SO2, a significant decrease in cell voltage and an increase in F− release rate were observed. The electrolyte degradation appears to be accelerated by hydroxyl radicals generated from H2O2, which was produced by a sulfur-poisoned Pt catalyst. 19F-NMR analysis of the sulfur-poisoned MEA revealed that the degradation of the cathode ionomer was significant compared to the anode ionomer and the membrane. Degradation of the cathode ionomer was confirmed by experiment with the MEA composed of a hydrocarbon-based membrane and a perfluorosulfonic acid ionomer, in which an increase in the F− release rate was also observed.
Carbon-free Pt Electrocatalysts Supported on Doped SnO2 for Polymer Electolyte Fuel Cells
Authors: Takasaki Fumiaki , Noda Zhiun , Masao Akihiro , Shiratori Yusuke , Ito Kohei , Sasaki Kazunari
Published: September 2009

Oxidation-induced carbon support corrosion especially in cathode electrocatalysts for polymer electrolyte fuel cells (PEFCs) is one of the important technological issues to be solved. We focus our attention to SnO2, known as a broad-band oxide semiconductor with a high electronic conductivity, as a possible electrocatalyst support material. In this study, nanostructure, electrochemical properties and durability of carbon-free electrocatalysts, Pt/SnO2, Pt/Nb-SnO2, Pt/Al-SnO2, are investigated.
Sulfonated Poly-Aryl-Ether-Ketones for Applications in Carbon-Nano-Fiber based Membrane-Electrode-Assemblies
Authors: Perchthaler Markus , Wallnöfer Eva , Hacker Viktor
Published: September 2009

The synthesis of sulfonated polyetheretherketones (SPEEK) with three different sulfonation levels was carried out and several membranes were developed with the corresponding polymers. The membranes were characterized by determining Ion Exchange Capacity (IEC), water uptake and the results were correlated to electrochemical data. Electrochemical tests were performed in a single cell fed with H2/O2 at a temperature of 60 {degree sign}C and compared to commercial Nafion 112 (N112). A maximum power density of 30 mW cm-2 was obtained, and the measured OCV value for the SPEEK membrane was lower than the perfluorinated membrane, indicating a higher gas permeability of the thinnest SPEEK polymer membranes.
Nafion-Mesoporous Silica as Electrolyte for Ethanol Fuel Cells
Authors: Ahmed Zakarya , De Matos Bruno R. , De Florio Daniel Z. , Licoccia Silvia , Traversa Enrico , Esposito Vincenzo , Santiago Elisabete I. , Fonesca Fabio Fonseca C.
Published: September 2009

Commercial Nafion was used as polymer matrix for synthesized mesoporous silica with medium surface area. The synthesized mesoporous silica was characterized by BET, SEM and TEM demonstrating the formation of a organized pore structure of the silica. The composite with 5% of the filler was characterized by thermogravimetry and impedance spectroscopy. Polarization curve of the composite was also conducted at 80{degree sign}C and 130 {degree sign}C, confirming the enhancement of the ethanol fuel cells performance.
Corrosion Resistance, Cell Performance and Long-term Stability of Metal Bipolar Plates for Direct Methanol Fuel Cell
Authors: Park Young-chul , Peck Dong-Hyun , Jung Doo-Hwan , Kim Sang-Kyung , Lim Seongyop , Lee Dokyol
Published: September 2009

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 DMFC. This work was carried out to offer fundamental information about metal bipolar plates of DMFC because there are few literatures relevant to the subject. The corrosion behaviors of these metals were studied in the simulated fuel cell environment, and then their single cell performance and long-term stability were tested at real operating conditions of DMFC.
Effect of Gas Diffusion Layer Composition on the Performance of Liquid Direct Methanol Fuel Cells
Authors: Alcaide Francisco , Alvarez Garbiñe , Querejeta Amaia , Miguel Oscar , Boyano Iker
Published: September 2009

The effect of gas diffusion layer compositions on the performance of liquid feed direct methanol fuel cell has been investigated. Cathode diffusion layers consisting of carbon paper with different microporous layer compositions have been fabricated. Specifically, we have modified the carbon material used in microporous layers. Morphological and textural properties of different cathode diffusion layers were characterized and related to the performance obtained in single cell experiments. We have found that using a microporous layer made with an acetylene black instead of a furnace carbon black resulted in higher cell voltages in the entire current density region, as well as, higher maximum power density. This was attributed in first instance to the decrease of mass transfer resistance in the oxygen diffusion layer as a consequence of the microstructure of microporous layer.
Effect of Nanocarbon Substrate Materials on the CO Tolerance of PtRu Electrocatalysts for Fuel Cell
Authors: Yoo EunJoo , Takano Yukio , Nakamura Junji
Published: September 2009

The support effect of carbon nanotubes (CNTs) on the performance of CO tolerant electrocatalysts for polymer electrode fuel cell (PEFC) was studied by preparing identical Pt-Ru catalyst particles in a liquid phase and then attaching them on CNTs with different diameter (15-100 nm) and specific surface area. The Pt-Ru catalysts supported on a thinner multi-walled CNT with the diameter of 15 nm shows higher CO tolerance performance in the hydrogen oxidation reaction (HOR). It is thus considered that the CO tolerance of Pt-Ru electrocatalyst is significantly dependent on the kind of CNTs surface.
Analysis of Proton Transport in Pseudo Catalyst Layers: Influence of Ionomer Content
Authors: Iden Hiroshi , Ohma Atsushi , Yamaguchi Koichi , Shinohara Kazuhiko
Published: September 2009

The influence of the ionomer content on proton transport phenomena in the catalyst layers of a fuel cell was examined using pseudo catalyst layers (PCLs) consisting of carbon support and the ionomer. Effective proton conductivity of the PCL became greater with increasing ionomer content in both ketjen black (KB) and graphitized ketjen black (GKB) systems. Based on the analyses, it was found that the ionomer coverage and the Bruggeman factor which is related to the tortuosity of the proton path in the PCL did not depend on the ionomer content appreciably. Therefore, the proton conductivity of the ionomer as bulk probably differs depending on the ionomer content. The results of a water adsorption analysis suggested that the water adsorbability of the ionomer varied according to the ionomer content in the KB system. Although the ionomer content does not affect water adsorbability, it could change the morphology of adsorbed water in the GKB system.
Influence of Sulfonating Agent on Degree of Functionalisation and Properties of Sulfonated Ether-linked Polybenzimidazole
Authors: Ng Feifei , Donzel Nicolas , Jones Deborah J. , Rozière Jacques , Bauer Bernd , Schuster Michael , Jeske Michael
Published: September 2009

A novel type of polybenzimidazole containing cross-linkable phthalidene groups has been functionalized by direct sulfonation for use as a fuel cell membrane via electrophilic substitution using both concentrated and fuming sulfuric acid. This novel ether-linked polybenzimidazole presents different types of site for substitution. A broad study of the influence of the reaction conditions shows that the degree of sulfonation and the site of sulfonation have a clear dependence on the nature of the sulfonating agent, with less activated sites being sulfonated even for short reaction times using oleum. The sulfonation sites have been identified using 2D COSY 1H NMR and the extent of sulfonation confirmed using elemental analysis. Polymers having degrees of sulfonation up to ca. 5 meq g-1 have been obtained, which are insoluble in water but soluble in polar aprotic solvents, enabling elaboration of solution-cast membranes that have conductivity >20 mS cm-1.
Dynamic Measurement and Modeling of the Water Vapor Concentration during ac Impedance Measurements in Polymer Electrolyte Fuel Cells (PEFCs)
Authors: Bayer Michael H. , Wokaun Alexander , Scherer Guenther G. , Schneider Ingo A.
Published: September 2009

The build up of water concentration oscillations along the flow channels of a low humidity polymer electrolyte fuel cell (PEFC) during ac impedance measurements is investigated. A pseudo 2D PEFC transient model is presented to describe the effect of ac current on the local water concentration in the flow channels. Furthermore, the frequency response of the water concentration in the anode and cathode exhaust gas is measured in situ via tunable diode laser absorption spectroscopy. The results show a strong dependence of the local phase and amplitude on modulation frequency. At higher modulation frequencies the water concentration oscillation in the membrane and in the gas channels is very small (f{greater than or equal to}10Hz). However, at frequencies below f=1Hz the water concentration oscillations start to penetrate into the membrane, and water vapor concentration oscillations build up along the flow channels. This process governs the impedance response of a low humidity PEFC at low frequencies.
Electrochemical Impedance Spectroscopy of Proton Exchange Membrane Fuel Cells (PEMFC) Using Embedded Probes
Authors: Abbaraju Ravikanth , Dasgupta Niladri , Virkar Anil V.
Published: September 2009

Three cast Nafion membranes were laminated with two silver mesh (screens) to form proton exchange membrane fuel cells (PEMFC) with embedded reference electrodes. Performance characteristics of the PEMFC were evaluated at 80oC with humidified (100% RH) H2 and air or O2 as fuel and oxidant respectively. Impedance spectra were obtained between the cathode and the anode, between the reference electrodes and the cathode, between the reference electrodes and the anode, and across the reference electrodes under various loads. DC voltage between the reference electrodes and the cathode and the anode were also measured at various loads. Individual electrode polarizations were obtained from impedance spectra. The results showed that cathode polarization was greater than anode polarization. Also, the cathode exhibited significant concentration polarization.
Wetting and Drying Responses of Gas Diffusion Layers and Proton Exchange Membrane to Current Transients
Authors: Davey John R. , Mukundan Rangachary , Spendelow Jacob S. , Mukherjee Partha P. , Hussey Daniel S. , Jacobson David L. , Arif Muhammad , Borup Rodney
Published: September 2009

This study examined the hydration state of the PEM and GDLs in four PEM fuel cells, with various combinations of SGL Carbon carbon paper GDLs with different PTFE loadings, in response to current step up and step down transients. The goal was to determine the effect of these GDLs and their PTFE loadings in the substrates and MPLs on the water dynamics and performance. The fuel cells used GoreTM MEAs and were operated at 80oC with stoich tracking gas flows at 50% inlet RHs. In situ HFR measurements were used for monitoring PEM hydration and in situ neutron imaging of the fuel cells was conducted at NIST with quantitative analysis to determine the liquid water content in the GDLs and channels. High PTFE loadings in the porous, open GDL substrates allow for greater water flux and lower water holding capacity, which facilitates cathode reaction water removal at high currents. In contrast, high PTFE loadings in the less porous, smaller pore size MPLs increase the water barrier attributes and seal in PEM water. Counter flow gas feed results in more even water distribution than co-flow feed. Counter flow feed with cathode air flowing against gravity increases cell hydration in dry operating conditions.
Investigation and Modeling of Carbon Oxidation of Pt/C under Dynamic Potential Condition
Authors: Takeuchi Norimitsu , Jennings Emily , Fuller Thomas F.
Published: September 2009

The degradation of catalysts in Proton Exchange Membrane Fuel Cells (PEMFCs) has been a major challenge for vehicle and stationary usage of PEMFCs. As carbon loss (carbon corrosion) phenomena have been reported elsewhere, some mitigations have been suggested (1-5), although the oxidation mechanism of carbon on Pt/C has not been elucidated. In order to improve the durability of carbon materials in PEMFCs more effectively, it is necessary to understand the oxidation mechanism of carbon on Pt/C catalyst, especially under dynamic potential conditions. In this report, the acceleration of carbon oxidation by Pt is confirmed experimentally and the carbon oxidation mechanism under dynamic potential conditions is discussed with the aid of a model and simulation analysis. It is estimated that Pt-OH species significantly affects carbon oxidation on Pt/C surface when the potential is under 1.0 V. The numerical results support the acceleration of carbon oxidation by Pt on Pt/C surface.
In Situ GIXAFS and HERFD-XAS Studies of a Pt-modified Rh(111) Electrode
Authors: Friebel Daniel , Miller Daniel , Ogasawara Hirohito , Anniyev Toyli , Bergmann Uwe , Bargar John , Nilsson Anders
Published: September 2009

The oxygen reduction reaction at Pt electrodes has a high overpotential which reduces the efficiency of fuel cells. The origin of the overpotential has been seen in the formation of stable Pt-O species at high potentials. Aiming at an unambiguous characterization of such species, we use in situ grazing incidence x-ray absorption spectroscopy at the Pt L3 edge to study the geometric and electronic structure of ultrathin Pt layers on M(111) substrates. We present Pt L3-edge grazing incidence x-ray absorption fine structure (GIXAFS) and high energy resolution fluorescence detection (HERFD) XAS measurements of Pt/Rh(111) in 0.01 M HClO4 solution. In the HERFD-XAS experiment, we used a multi-crystal analyzer to suppress the core hole lifetime broadening. The HERFD spectra reveal additional spectral features of the near-edge region which can be important for an accurate structure model of the Pt/electrolyte interface.
Designing a New Ionomer from Scratch - Pushing Polypoms to the Limit
Authors: Horan James L. , Kuo Mei-Chen , Sachdeva Sonny , Ren Hui , Perdue Andrew S. , Dec Steven F. , Yandrasits Michael A. , Hamrock Steven J. , Frey Matthew H. , Herring Andrew M.
Published: September 2009

We have fabricated proton conducting films using monomers based on vinyl substituted silicotungstic acid heteropoly acids (HPAs) and acrylate co-monomers. In this work we probe the limits of this system based on increasing the weight loading of the HPA to 85 wt%. Although impressive proton conductivities can be achieved with these films under hotter and drier operating conditions than in conventional proton exchange membranes, the materials have mechanical limitations. We show that very different film morphologies can be prepared based on whether or not the film is polymerized thermally or by UV light. In general the UV cured films have superior proton conductivity, but have a linear morphology resulting in a brittle film. The thermally cured films have a clustered morphology with good mechanical attributes but have poor proton conductivity.
Functionalized Hybrid Organic-Inorganic Membranes Investigated by ac-Electrogravimetry
Authors: Debiemme-Chouvy Catherine , Gabrielli Claude , Laberty-Robert Christel , Perrot Hubert , To Thi Kim Loan , Sel Ozlem
Published: September 2009

In this paper, original hybrid membranes, made through sol gel techniques, were characterized by using ac-electrogravimetry measurements. In order to perform experiments, a polypyrrole-heteropolyanion film was generated between the working electrode of the microbalance and the hybrid film. This mediator mixed conducting membrane is necessary to provide protons transfer between the different interfaces and therefore, proton transport inside the hybrid film which is only an ion conductor. If the classical proton transfer was demonstrated, the role of the free solvent was also pointed out: the relative species concentration, separately for each species, charged or not, was estimated according to the applied potential.
Composite Proton Conductive Membranes for Elevated Temperature and Reduced Relative Humidity PEMFC
Authors: Chalkovaa Elena , Wang Chunmei , Komarneni Sridhar , Lee Jeoung , Fedkin Mark , Lvov Serguei
Published: September 2009

Nafion/inorganic (inorganic = S-ZrO2, SiO2-SO3H, SBA-15-SO3H, MCM-41-SO3H, and P-Si gels) composite membranes were synthesized with the goal of increasing the proton conductivity and water retention at elevated temperatures up to 120 {degree sign}C and reduced relative humidity (RH) down to 25%. Inorganic materials were incorporated within the Nafion by three different techniques. The addition of inorganic particles increased the membrane ion exchange capacity (IEC). The conductivity of composite membranes with sulfonated inorganic materials was in agreement with their IEC but not higher than the conductivity of the recast Nafion in the whole range of inorganic loading. Conductivity of the Nafion/P-Si gel membranes was affected by the surface of inorganic powders and was higher for membranes prepared by in situ formation techniques. Effect of the inorganic phase on membrane performance in a fuel cell was much stronger than on its conductivity due to substantial improvement in membrane water retention properties.
Nafion/Acid Functionalized Mesoporous Silica Nanocomposite Membrane for High Temperature PEMFCs
Authors: Chen Zhongwei , Hsu Ryan
Published: September 2009

This study reports the synthesis and the characterization of proton conducting composite membranes prepared by dispersing in Nafion matrix with highly acid functionalized mesoporous silica (KIT-6). Nafion/KIT-6 composite membranes were studied for operation in hydrogen/oxygen polymer electrolyte membrane fuel cells (PEMFC) at 120 {degree sign}C with different relative humidities (72%RH and 100%RH). The Nafion/KIT-6 composite membrane demonstrated little improved fuel cell performance to that of the Nafion membrane at 100% relative humidity (RH), however, it was much higher at low RH (72%). These results suggest that this new type of Nafion composite membrane may be successfully used as an improved proton exchange membrane in high temperature PEMFC.
Mechanistic Aspects of Ethanol Electro-oxidation in Unsupported Platinum Nanoparticles
Authors: Cantane Daniel A. , Gonzalez Ernesto R.
Published: September 2009

Parallel reaction pathways are possible during ethanol electro-oxidation at un-supported platinum nanoparticles. In the present paper, the effect of the base electrolyte namely HClO4 (0.1 mol L-1) and H2SO4 (0.5 mol L-1) is reported for ethanol (0.01 mol L-1)electro-oxidation. Electrochemical studies and in situ FTIR showed lower catalytic activity for the oxidation in H2SO4 than in HClO4 for 0.01 mol L-1 ethanol. This indicates that the strong adsorption of sulfate in (111) domains inhibits the dissociative adsorption of ethanol. This is evidenced by in situ FTIR where it is noted the emergence of the COads (COL 2040 cm-1) band at 0.05 V in perchloric, and only at 0.4 V in sulfuric media. The oxidation of 0.01 mol L-1 ethanol follows only the CO2 pathway in the two acid electrolytes.
Platinum/Tin Oxide - Single Walled Carbon Nanotube Electrocatalysts for Direct Ethanol Fuel Cell
Authors: Hsu Ryan , Chen Zhongwei
Published: September 2009

A novel tin oxide (SnO2) coated single-walled carbon nanotubes (SWCNT) supported platinum (Pt) electrocatalyst were developed for direct ethanol fuel cells (DEFCs). SnO2 coated SWCNT were synthesized successfully with a simple method of hydrolysis-oxidation of SnCl2 in water at room temperature, then SnO2-SWCNT supported Pt electrocatalyst (Pt/SnO2-SWCNT) and SWCNT supported Pt electrocatalyst (Pt/SWCNT) were prepared by an ethylene glycol (EG) reduction method. The Pt/SnO2-SWCNT catalyst demonstrated much higher catalytic activity for ethanol oxidation reaction (EOR) than that of the Pt/SWCNT.
Estimation of Local Relative Humidity in Cathode Catalyst Layers of PEMFC
Authors: Gazzarri Javier , Xia Zetao , Zhao Xinsheng , Wang Qianpu , Eikerling Michael H. , Liu Simon , Xie Zhong
Published: September 2009

A method is presented to estimate the local relative humidity in cathode catalyst layers of PEM fuel cells. Based on impedance measurements under different experimental conditions, this technique allows the estimation of an average value for relative humidity using a correlation with the catalyst layer effective proton resistance. A fully humidified anode was found to increase the relative humidity of the nominally drier cathode because of water permeation through the membrane, to as much as almost 70% for a nominal 30% when the anode RH was held at 100%.