bluuebunny/crossref_metadata_2025 huggingface dataset:
Reservoir architecture of the Gharif Formation outcrops in the Southern Huqf area, Sultanate of Oman
Authors: Alsop D. B. , Al Ghammari M. , Al Abri A. , Al Mahrooqi A. , Al Rawahi H. , Salem H.
Published: October 2013

The Gharif Formation was deposited in the early Permian and is one of the major producing oil and gas reservoirs in the Sultanate of Oman. The Upper Gharif Unit crops out at Wadi Gharif, where a detailed outcrop characterization was undertaken. Fluvial channel sandstones, inclined heterolithic stratification (IHS) and floodplain palaeosols are the dominant facies associations. Deposition was in a low to moderate sinuosity multistorey fluvial channel belt with fluctuating water levels, allowing water retention in the channel while mud deposited on the upper portions of the point bar was exposed. Sandstone-body geometries indicate ribbon-like channels flowing in a NW orientation. The channel belt is estimated to be between 150 and 250 m wide and encased in oxidized red palaeosols. The depositional units are stacked from east to west and the scour and erosional surfaces are indicative of cut and fill under relatively low accommodation conditions. The reservoir architecture highlights the presence of potential claystone baffles in the IHS section on the margins of the point bars. Differences in grain size between the coarse-grained channel sandstones and the fine-grained IHS sandstones potentially create a permeability contrast while the inclined surfaces will affect fluid movement for both vertical and lateral flow. A deterministic surface-based model was constructed to access static connectivity of the Gharif fluvial channels.
Standardizing Thin-Film Rotating Disk Electrode Measurements of the Oxygen Reduction Activity of Pt/C
Authors: Garsany Yannick , Ge Junjie , St-Pierre Jean , Rocheleau Richard , Swider-Lyons Karen
Published: October 2013

Rotating disk electrode voltammetry has been touted as a simple means for benchmarking the oxygen reduction activity of platinum-based catalysts in proton exchange membrane fuel cells. The RDE methodology is still highly variable across laboratories, and due to differences in experimental conditions, up to 2.5x differences in mass activities are reported in recent literature from the same catalyst. We demonstrate an RDE protocol, and show that it can be replicated in two different laboratories. Uniform RDE methodology should be developed so that advanced catalysts can be compared between laboratories.
Enhanced Oxygen Reduction Activity on Pt/C for Nafion-free, Thin, Uniform Films in Rotating Disk Electrode Studies
Authors: Shinozaki Kazuma , Pivovar Bryan S , Kocha Shyam S
Published: October 2013

Commercially available nanoparticle platinum on high surface area carbon black (Pt/HSC) electrocatalysts were characterized in rotating disk electrode (RDE) setups using varying ink formulations and film drying techniques in an attempt to obtain thin, uniform films and reproducible activity. Electrodes prepared from Nafion-free inks that were dried under an isopropyl alcohol (IPA) atmosphere produced uniform, thin films at low electrocatalyst loadings of ~4.5 mg/cm2
Pt. These Nafion-free/IPA-dried electrodes were found to exhibit oxygen reduction reaction (ORR) activities higher than conventional Nafion-based/Air-dried electrodes by a factor of ~2.8. The magnitude of mass and specific activities were determined to be im~771 ±56 mA/mgPt and is~812 ±59 mA/cm2
Pt respectively and appear to be the highest values reported for RDE measurements on Pt/HSC in 0.1M HClO4 at 20 mV/s and 25oC. Electrochemical diagnostics including ORR I-V profiles, cyclic voltammograms and electrochemical impedance spectroscopy (EIS) studies were conducted to investigate the thin film Pt/HSC electrodes and correlate results to film morphology and electrochemical activity.
Pt Nano-Particle Performance for PEFC Reactions at Low Catalyst Loading and High Reactant Mass Transport
Authors: Zalitis Christopher Mark , Kramer Denis , Sharman Jonathan , Wright Ed , Kucernak Anthony Robert
Published: October 2013

The rotating disk electrode (RDE) is currently the favored technique for fundamental research on electrocatalysts for polymer electrolyte fuel cells (PEFC). However, being submerged in liquid electrolyte limits the over-potential range that can be studied before mass transport effects become dominant. State of the art PEFCs operate under much higher mass transport regimes and over wider potential ranges than cannot be accessed with the RDE. This may limit the usefulness and applicability of RDE results to PEFCs. Here we present recent progress in the development of electrodes for liquid and solid polymer electrolytes which achieve high mass transport. The electrodes are fabricated using a simple deposition process which produces a flat, uniform, and homogeneous catalyst layer. This allows for rapid screening of catalysts across the entire working conditions of a PEFC with minimal mass transport effects. Additionally, we show this technique can be used for electrolyser research.
Development of Advanced Electrocatalyst for Automotive Polymer Electrolyte Fuel Cells
Authors: Sugawara Seiho , Arihara Kazuki , Tanaka Hiroyuki , Ohwaki Tsukuru , Mitsumoto Hisashi , Sekiba Toru , Shinohara Kazuhiko
Published: October 2013

Reduction of Pt loading on fuel cell electric vehicles is strongly desired for fuel cell electric vehicles to be commercially viable. Activity enhancement for the sluggish oxygen reduction reaction of Pt-based electrocatalyst is the most essential to reduce Pt loading. Here, we provide a brief review of recent advances in Pt-based ORR electrocatalysts followed by electrocatalyst research activities of Nissan.
Nonlinear Diffusion Analysis of the Voltage Signal of a Polymer Electrolyte Fuel Cell with Cathode Water Accumulation
Authors: Burkholder Michael , Litster Shawn
Published: October 2013

In polymer electrolyte fuel cells (PEFCs), cathode water accumulation can have negative effects on fuel cell performance if not properly managed. In order to further understand the nonlinear and oftentimes chaotic dynamics associated with cathode water generation and removal, we apply a nonlinear analysis to the PEFC voltage signal. We examine scale invariance in the frequency power spectra of the fuel cell voltage signal at varying current densities. We also estimate the Hurst exponent of the PEFC voltage with a diffusion analysis. We find that both the scale invariance and the Hurst exponent are able to indicate differences in the dynamics from cathode microchannel flooding. The results are applicable to PEFC water management.
Optimized Flow Distribution for Enhancing Temperature Uniformity across an Open Cathode PEM Fuel Cell Stack
Authors: Thomas Sobi , Kwon Osung , Lee Sang C. , Park Sam , Choi G.H. , Choi J.Y.
Published: October 2013

The objective of this work is to develop a stable energy source based on renewable energy for powering an in-house developed unmanned robot. The major challenges are firstly to design a power source with higher energy density and secondly to develop a compact design (low volume and light weight stack) suitable for integrating with the in house robot platform. To overcome the aforementioned challenges, the study aims at designing an open cathode low temperature polymer electrolyte membrane fuel cell (PEMFC) system to be coupled with a battery to serves as an efficient power source. The major part of the work involves the design of compact fuel cell system. In a fuel cell the serpentine flow channel is considered to optimal because it has the advantage of uniform flow distribution, but with higher pressure drop. Because of the higher pressure drop a pump is required to supply the oxidant for chemical reaction. But with lower pressure drop and fairly uniform flow distribution open cathode stack design is developed, that facilitates the use of blower which consumes less power. Also the overall system volume can be reduced with higher efficiency.
Spatially and Temporally Resolved Measurement of Water Distribution in Nafion Using NMR Imaging
Authors: Klein Mathieu , Perrin Jean-Christophe , Leclerc Sébastien , Guendouz Laouès , Dillet Jérôme , Lottin Olivier
Published: October 2013

The hydration conditions of the membrane can vary widely over short timescales during the operation of a PEMFC. To better understand the factors limiting water transport through the PEM membrane exposed to different boundary conditions we implemented a 1D NMR imaging method using a surface probe. This methodology offers a high temporal resolution, allowing the detailed monitoring of fast transient phenomena.
Evaluation of Transient Water Content during PEMFC Operational Cycles By Stroboscopic Neutron Imaging
Authors: Fairweather Joseph D. , Spernjak Dusan , Spendelow Jacob , Mukundan Rangachary , Hussey Daniel S , Jacobson David L , Borup Rod L
Published: October 2013

A method is demonstrated for increasing the effective temporal resolution of neutron imaging, by averaging a consistent time window across multiple PEMFC operational cycles. Rapid water transients are captured during the current density and humidity changes of a cell durability protocol. The response of different cell components is compared by in-plane imaging, while temperature variation and upstream effects are observed by through-plane imaging of larger cells.
Distinction of Liquid Water and Ice Based on Dual Spectrum Neutron Imaging
Authors: Biesdorf Johannes , Oberholzer Pierre , Bernauer Felix , Kaestner Anders , Vontobel Peter , Lehmann Eberhard , Schmidt Thomas J. , Boillat Pierre
Published: October 2013

This study investigates a new approach to distinguish liquid water and ice based on dual spectrum neutron imaging. The imaging technique benefits from arising differences between the cross section of water and ice at neutron wavelengths above 3 Å. As a significant portion of the energy spectrum of the ICON beamline at PSI is below 3 Å, no differences can be observed with the entire beam. However, introducing a Beryllium neutron filter inside the beam, the interesting region of the spectrum is emphasized resulting in a significant contrast of approximately 1.8% between the aggregate states of liquid and frozen water.
Investigation of Liquid Water Accumulation in Operating PEM Fuel Cells With/Without MPL and Its Effect on Cell Performance
Authors: Deevanhxay Phengxay , Sasabe Takashi , Tsushima Shohji , Hirai Shuichiro
Published: October 2013

In situ visualization of liquid water distribution in PEM fuel cell with and without MPL and its effect on the fuel cell performance was investigated. The liquid water accumulation at the interface of catalyst layer (CL) and gas diffusion media (GDM) was observed to have large impact on the performance of fuel cell without MPL. The MPL reduces the liquid water at the interface of CL and GDM and enhance the performance of the fuel cell with MPL. The effect of gas flow rate on the liquid water distribution and performance of the fuel cell with MPL was also studied. The higher water content at the cathode MPL/GDL boundary was observed and corresponds for the large decreasing in cell voltage when lower the gas flow rate.
Visualization of Gas Bubble Behavior of a Regenerative Fuel Cell in Electrolysis Mode by Soft X-ray Radiography
Authors: Selamet Omer Faruk , Deevanhxay Phengxay , Tsushima Shohji , Hirai Shuichiro
Published: October 2013

Regenerative fuel cells (RFC) are candidates for hydrogen energy to become common in daily life since it lowers the first investment cost by combining two different devices into one. In an earlier study, it is proved that the hydrogen mass transport was limited by water accumulation, hence lowers the cell efficiency. Soft X-Ray radiography experiments performed to investigate hydrogen and oxygen gas bubble behavior in a regenerative fuel cell. The cell was visualized with high spatial resolution at different current densities. The hydrogen gas bubbles appear first compared to the oxygen, since the higher stoichiometric hydrogen generation and lower solubility of hydrogen in water. The gas bubbles tend to nucleate at certain locations which are thought to be cracks on the catalyst layer.
Polysulfone-Based Electrospun Anion Exchange Membranes
Authors: Park Andrew Michael , Turley Forbes Ellington , Wycisk Ryszard , Pintauro Peter N.
Published: October 2013

Nanofiber composite anion exchange membranes were prepared from crosslinked and quaternized polysulfone fibers embedded in a polysulfone matrix. Polysulfone with a mixture of chloromethyl and iodomethyl groups and containing a controlled amount of a diol crosslinker was simultaneously electrospun with polyphenylsulfone. The resultant anion exchange dual nanofiber mat was subsequently processed into a dense and defect-free membrane by: (i) compaction on a hydraulic press, (ii) heating to crosslink the chloromethyl/iodomethyl fibers, (iii) exposure to chloroform which softened the polyphenylsulfone and allowed it to flow between crosslinked fibers, and (iv) quaternization with trimethylamine. The final composite membrane exhibited good conductivity in room temperature water (54 mS/cm) with a water swelling of 118% and a wet membrane stress-at-break of 23 MPa. While the IEC of the quaternized nanofibers was higher than the polymer solubility limit in water, no weight loss was observed upon membrane equilibration in room temperature water, due to the presence of crosslinks.
Interaction and Transport of Carbon Dioxide in Alkaline Anion Exchange Membranes
Authors: Myles Timothy D. , Ren Xiaoming , Grew Kyle N. , Chiu Wilson K. S.
Published: October 2013

Transient measurements of CO2 cross-over through Tokuyama A201 membranes were made utilizing a permeation cell setup. The transient data was analyzed using a classical Fickian based model. Results were compared to Nafion 117 and it was found that the characteristic behavior of the transient data was different between the two membranes. Nafion 117 followed closely with the exponential behavior dictated by the Fickian based model while the A201 membrane displayed a behavior more closely resembling a sigmoid curve. The reason for this behavior is hypothesized to be related to either a breakdown of the modeling assumptions or the interaction of the alkaline membrane with CO2.
Micro-Computed Tomography Imaging of HT-PEM Fuel Cells under Contact Pressure Control
Authors: Rastedt Maren , Pinar Francisco Javier , Bruns Nadine , Diedrichs Anja , Wagner Peter
Published: October 2013

In order to increase the efficiency of nowadays fuel cells it is important to understand degradation processes. This paper focuses on defects related to compression of the Membrane-Electrode-Assembly. A particular useful tool therefore is the micro-computed tomography, as it allows a non-destructive insight into the MEA. The results from this imaging method are compared to classical electrochemical characterizations procedures. MEAs with different Gas Diffusion Layers (cloth and paper) are investigated and their individual behavior upon compression is evaluated.
Oxygen Reduction Reaction Activity of Pt/Ni/Pt(111) Well-defined Model Catalyst Surfaces
Authors: Todoroki Naoto , Asakimori Yu , Wadayama Toshimasa
Published: October 2013

In this study, wWe have investigated the oxygen reduction reaction (ORR) activity of Pt/Ni/Pt(111) model catalyst surfaces prepared by molecular beam epitaxy. Compared with Pt(111), The 1–-4- monolayers (MLs)-thick Pt on Ni/Pt(111) surfaces showed 9-, 12-, 8-,, and 7-fold higher activities, respectively than that of Pt(111). Cyclic voltammetry measurements and X-ray photoelectron spectroscopic analysis clearly revealed that electrochemical as well asand electronic properties of the surface Pt(111) surface lattice approach those ofcome close to clean Pt(111) surface with increasing Pt’s surface layer thickness. The results demonstratedexhibited that tuning Pt shell thickness is a key for generating highly- active Pt-bimetallic catalysts of for ORR.
Structural and Compositional Behaviors of Shaped Pt Alloy Nanoparticle Electrocatalysts
Authors: Cui Chunhua , Gan Lin , Heggen Marc , Strasser Peter
Published: October 2013

We present the design and synthesis of phase segregated Pt alloy nanoparticle electrocatalysts through a facile solvothermal route in a dimethylformamide solvent. The compositional segregation near the alloyed PtNi nanoparticle surface was achieved by controlling the reaction kinetics and site-dependent compositional segregation in the facet centers of the shaped PtxNi1-x nanoparticles was controlled by the bulk Pt/Ni composition ratio, respectively. Based on this unique compositional segregation, we study their atomic-scale evolution of surface microstructure and composition by using high-resolution scanning transmission electron microscopy with high angle annular dark field and electron energy loss spectroscopy line scans and investigate their structural and compositional behaviors under reactive environments. The surface evolution of these materials helps ones understand the reactivity and degradation of a catalyst and understand the interactions between reactants and catalysts by introducing environmental impact factors.
Pt-Cu Alloys as Catalysts for the Oxygen Reduction Reaction – A Thin-Film Study of Activity and Stability
Authors: Schuppert Anna K. , Topalov Angel A. , Savan Alan , Ludwig Alfred , Mayrhofer Karl J.J.
Published: October 2013

Critical factors for the commercial application of fuel cells are the high costs and the limited stability of Pt catalysts. In order to improve the activity and material efficiency, Pt-alloys with non-noble metals play an essential role. However, stability remains a critical factor for this type of catalysts. In order to understand the dissolution of Pt-alloys and eventually improve their performance, we therefore analyze a Pt-Cu thin-film alloy with varying composition using a combinatorial screening approach coupled to online analytics.
Palladium-Based Bimetallic Catalysts for Alkaline Direct Alcohol Fuel Cell (ADAFC)
Authors: Jurzinsky Tilman , Cremers Carsten , Pinkwart Karsten , Tübke Jens
Published: October 2013

This work investigated carbon supported Pd, PdNi and PdAg electrocatalysts for electrooxidation reactions of methanol and ethanol in alkaline media. The results show that Pd/C electrocatalysts alone have low activity and poor stability for the alcohol electrooxidation. Addition of metals like Ni and Ag significantly promotes the catalytic activity and stability of the electrocatalysts for the alcohol electrooxidation. The investigation of the influence of metal amount added to the Pd on the electrocatalyst shows that Pd3Ag1/C and Pd3Ni1/C are much more efficient than Pd/C for methanol electrooxidation while Pd5Ag1/C and Pd3Ag1/C are much more efficient than Pd/C for ethanol electrooxidation.
Trend in Oxygen Reduction Reaction on Transition Metal Oxide Surfaces
Authors: Suntivich Jin , Shao-Horn Yang
Published: October 2013

Perovskite transition metal oxides exhibit high electrocatalytic activities for both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER), comparable to the state-of-the-art precious metal/metal oxide catalysts in alkaline environment. To better understand the origin of these oxygen electrocatalytic activities, we survey physical-chemical trends in the perovskites and their relations to the ORR activity, from which we postulate the role of the electronic states in stabilizing the reaction intermediates and facilitating oxygen charge transfer. Our finding supports the role of the electronic states in governing the metal–oxygen bond strength and the degree of mixing between the metal and the oxygen states as the underlying physical-chemical properties that control the activities of the perovskite oxides for oxygen electrocatalysis.
The Role of Water Management on the Oxygen Transport Resistance in Polymer Electrolyte Fuel Cell with Ultra-Low Precious Metal Loading
Authors: Srouji AK K , Zheng Lijuan , Dross Robert , Mench Mathew M.
Published: October 2013

In this work, limiting current measurements were used to evaluate oxygen transport resistance in the catalyst layer of a polymer electrolyte fuel cell (PEFC). The pressure independent oxygen transport resistance in the electrode was evaluated with two different cell architectures, and two different cathode Pt loadings (0.4 and 0.07 mgPt.cm-2) on. The compounded effect of the flow field and Pt loading is used to identify the nature of the observed transport resistance, in order to improve the physical understanding of the nature of the oxygen transport resistance, shown to directly or indirectly scale with Pt loading in the open literature. By varying gas pressure and using low oxygen concentrations, the total oxygen transport resistance is divided into intermolecular gas diffusion (pressure dependant) and a pressure independent component, which could be attributed to Knudsen diffusion or dissolution film resistance. The pressure-independent oxygen transport resistance in the catalyst layer was measured to vary between 13.3 and 34.4 s/m. It is shown that the pressure independent oxygen transport resistance increases with reduced Pt loading, but that effect is exacerbated by using conventional channel/lands. The results indicate that the open metallic element architecture improves the oxygen transport resistance in ultra-low Pt loading electrodes due to enhanced water management at the catalyst layer.
The Impact of Fibre Surface Morphology on the Effective Thermal Conductivity of a PEM Fuel Cell Gas Diffusion Layer
Authors: Botelho Steven Joseph , Bazylak Aimy
Published: October 2013

In this work, the preliminary findings for determining the effect of fibre surface morphology on the effective thermal conductivity of the gas diffusion layer of a polymer electrolyte membrane fuel cell is presented. Atomic force microscopy was used to measure the fibre surface roughness and asperity height distribution for various fibres and locations along each fibre for Toray carbon paper TGP-H-120. The thermal contact resistance was measured using preliminary methods, which will be further advanced in the near future. Hertzian contact mechanics was used to validate the results obtained, and to compare with smooth fibre thermal contact resistance for rough and smooth fibres. The thermal contact resistance was determined for various angles of fibre orientation and contact forces; it was determined that values for rough fibre contact are on average twice that of the contact of smooth fibres.
Ice Crystallization During Cold-Start of a Proton-Exchange-Membrane Fuel Cell
Authors: Dursch Thomas J. , Liu Jianfeng F. , Trigub Gregory J. , Radke Clayton J. , Weber Adam Z.
Published: October 2013

Under subfreezing conditions, ice forms in the gas-diffusion (GDL) and catalyst layers (CL) of proton-exchange-membrane fuel cells (PEMFCs), drastically reducing cell performance. Although a number of strategies exist to prevent ice formation, there is little fundamental understanding of ice-crystallization mechanisms and kinetics within PEMFC components. We incorporate recently developed ice-crystallization kinetic expressions (1-3) within the CL and GDL of a simplified 1-D transient PEMFC cold-start model. To investigate the importance of ice-crystallization kinetics, we compare liquid-water and ice saturations, and cell-failure time predicted using our kinetic rate expression relative to that predicted using a thermodynamic-based approach. We identify conditions under which ice-crystallization kinetics is critical and elucidate the impact of freezing kinetics on low-temperature PEMFC operation.
Effect of Perforation Structure of Cathode GDL on Liquid Water Removal in PEFC
Authors: Okuhata Go , Tonoike Takeshi , Nishida Kosuke , Tsushima Shohji , Hirai Shuichiro
Published: October 2013

In order to alleviate water flooding in cathode electrode of polymer electrolyte fuel cell (PEFC), it is essential to understand the liquid water bahavior across porous media and design the optimum electrode structure for enhancing water drainage on cathode side. In this study, the liquid water transport in the cathode of an operating PEFC was visualized macro- and microscopically using optical techniques, and the effect of perforation structure of cathode gas diffusion layer (GDL) on the water removal and performance improvement was discussed. The perforated GDL was fabricated by electric discharge machining (EDM) and manual micro-drilling technique. It was found that the perforation holes machined by the micro-drilling promotes the liquid water discharge from the GDL and effectively reduces water accumulation in the cathode electrode, because the hydrophobic PTFE coating at the hole sidewall is not damaged.
Effect of Through-Plane Polytetrafluoroethylene Distribution in a Gas Diffusion Layer on a Polymer Electrolyte Unitized Reversible Fuel Cell
Authors: Hwang Chulmin , Ito Hiroshi , Maeda Tetsuhiko , Nakano Akihiro , Kato Atsushi , Yoshida Tetsuya
Published: October 2013

This study is an investigation into the relationship between through-plan polytetrafluoroethylene (PTFE) distribution on a gas diffusion layer (GDL) and unitized reversible fuel cell (URFC) performance. Titanium (Ti) - felt was used for the oxygen-side GDL and treated with 10wt.% PTFE dispersion to enhance hydrophobicity. The PTFE distribution dependence on the PTFE drying conditions was examined using scanning electron microscopy (SEM)-based energy dispersive X-ray spectroscopy (EDS) imaging. The EDS image maps revealed that the PTFE distribution strongly depended on the drying condition of the PTFE; drying under atmospheric pressure yielded a highly heterogeneous PTFE distribution in the through-plane direction, whereas drying under vacuum pressure yielded a relatively uniform PTFE distribution. The cell performance of URFC was then evaluated based on measured current-voltage characteristics during both electrolysis and fuel cell operation modes. Results verified that compared with non-uniform distribution, a uniform PTFE distribution in the Ti-felt GDL improved the fuel cell performance.
Multi-Layered Membrane Electrode Assembly Fabrication by Electro-Spraying
Authors: Oh JI-Won , Na Hyunwoong , Nahm Sahn , Kim Yonghwan , Choi Hanshin
Published: October 2013

Electro-spraying process is chosen for direct deposition of catalyst electrodes on proton exchange membrane. Catalyst ink is composed of J&M 40 wt. % Pt/C, Nafion ionomer, and isopropyl alcohol. After depositing catalyst electrode on both sides of membrane, MEA was heat treated in different temperature and environment and then linear polarization and electrochemical impedance spectroscopy were conducted. I-V polarization behaviors are dependent on the heat treatment condition: improvements in the activation polarization and ohmic loss but deterioration of concentration polarization. It may be due to the change of pore structure according to heat treatment. Besides the heat treatment, functional layer is designed to facilitate transfer reactions. Ionomer rich thin layer is inserted between membrane and electrode while thin film having lower ionomer content than electrode is deposited between electrode and gas diffusion layer. By inserting functional layer, concentration polarization resistance can be markedly reduced.
Numerical Analysis of PEMFC Unsteady Performance Considering Water and Thermal Transport
Authors: Fukuda Takanori , Sato Akira , Araki Takuto
Published: October 2013

Three-dimensional, non-isothermal, unsteady numerical model considering liquid water transport inside GDL has been developed, and the effect of water transport on cell performance has been investigated. We also conducted liquid water visualization by synchrotron X-ray and it was found that liquid water in GDL has extremely wide size distributions, and the distribution strongly varied by their creation processes. Then we assume that liquid water in GDL forms droplets which has different diameters and thermal conductivity and diffusion coefficient depend on the droplet size. In this paper, a numerical model considering liquid water transport in a flow channel and GDL has been developed, and it is discussed how droplets in GDL have an impact on steady and unsteady responses of PEMFC power generating characteristics. As a result , droplets in GDL have a lot of influence on voltage responses.
Quantum Chemical Analysis about Deprotonation Reaction of Sulfonic Group of Perfluorosulfonic Acid Species in the Low Hydration Level
Authors: Sakai Hironori , Tokumasu Takashi
Published: October 2013

In this study, we focused on the chemical feature about sulfonic group of perfluorosulfonic acid (PFSA) by first principle calculation in low hydration levels. Our study could elucidate two facts about the chemical property of PFSA, the one is why deprotonation reaction of sulfonic group of PFSA is not occurred in hydration level one and two and the other is notable feature of deprotonation reaction in hydration level three by B3LYP/6-311+G(d,p) level calculation. In the hydration level three, activation energy of deprotonation reaction of sulfonic group was 0.70 kcal/mol. Although this activation energy includes computational error, it is considered that this deprotonation reaction would proceed in the operation temperature of polymer electrolyte fuel cell smoothly. And total energy of product was lower than the reactant by 3.72 kcal/mol. From these results, deprotonation reaction of sulfonic group in hydration level three would proceed to product efficiently. In addition, reverse reaction is hard to occur by the thermal energy of 350 K which is operation temperature of polymer electrolyte fuel cell.
Preparation and Characterization of SPEEK/Silicotunstic Acid/Acid Functionalized Polysilsesquioxane Hybrid Composite Membranes for PEM Fuel Cells
Authors: Seesukphronrarak Surasak , Ohira Akihiro
Published: October 2013

We described the synthesis and properties of SPEEK/inorganic　fillers (silicotunstic　acid/acid functionalized polysilsesquioxane hybrid)composite membranes with the goal of increasing the proton conductivity. The membranes were characterized to determine the thermal stability, water uptake as well as proton conductivity. The flexible, tough, and transparent free-standing membranes were successfully obtained by the solution casting method. The results showed that the composited membranes possess excellent thermal stability as well as high proton conductivity over a wide range of relative humidity (30-95%RH). Therefore, these materials proved to be promising materials for use in fuel cell application as polymer electrolyte membranes.
Durability of Pt Catalysts Supported on Ordered Mesoporous Carbon for Proton Exchange Membrane Fuel Cells
Authors: Kim Nam-In , Seong Jinhae , Yang Min-Ji , Cho Sung-Hwa , Park Jun-Young , CHOI Hanshin , Joo Sang Hoon , Kwon Kyungjung
Published: October 2013

Ordered mesoporous carbons (OMCs) are investigated as support materials of Pt catalyst in proton exchange membrane fuel cells. Four types of Pt/OMC catalysts are prepared and their electrochemical performances and durability are evaluated by cyclic voltammetry and linear sweep voltammetry using a rotating disk electrode system. Pt nanoparticles of 2-3 nm seem to be uniformly dispersed on the supports regardless of the kind of OMC. The different pore structure between CMK-3 and CMK-5 affects the surface areas of carbon supports and the resulting Pt nanoparticles with indicating that larger surface area accompanies higher oxygen reduction reaction (ORR) activity. Although the graphitization of carbon support from CMK-3 to CMK-3G reduces the surface area of carbon support, the surface area and the ORR activity of Pt nanoparticles on CMK-3G are increased. In general, the reductions in electrochemical surface area (ECSA) and ORR activity become more noticeable in proportion to the initial ECSA and ORR of Pt/OMC after accelerated durability test.
Electrochemical Behavior of Pd-based Nanocatalysts (Hollow@Me@Pd/C) in Direct Alcohol Oxidation in Alkaline Medium
Authors: Da Silva Rodrigo Garcia , De Andrade Adalgisa Rodrigues
Published: October 2013

The synthesis and application of core@shell nanocatalysts with high morphological organization has become an attractive research area, with potential application in fuel cell devices. Although the use of this class of nanocatalysts has increased, their catalytic performance and oxidation behavior toward alternative fuels such as ethanol, ethylene glycol, and glycerol remain to be elucidated. This paper describes the electrochemical characterization of the Pd-based catalyst (Hollow@Me@Pd/C, Me = Ru, Ni, and Sn), applied to the electrooxidation of ethanol, ethylene glycol, and glycerol in alkaline medium. The nanocatalysts were prepared by the co-reduction method; NaBH4 and sodium dodecylsulfate (SDS) were used, to promote an electrostatically self-assembled organization. The nanocatalyst compositions responded well in terms of fuel oxidation. Chronoamperometry results indicated the following order of reactivity: ethylene glycol < ethanol < glycerol. The best catalyst composition for glycerol was Hollow@Ni@Pd/C.
Effect of SiO2 Additive in Catalyst Layer and Electrolyte on the Performance for Mesothermal Fuel Cell Using Room Temperature Molten Salts
Authors: Uryu Hazuki , Kohno Yuji , Matsuzawa Koichi , Mitsushima Shigenori
Published: October 2013

Solid acid additive such as SiO2 to a room temperature molten salts (RTMs) applied membrane, which is a mesothermal fuel cell electrolyte without humidification, improves ionic conductivity and compression strength. However, the effect of SiO2 additive on the performance of the PEFCs is not yet clarified. In this study, we determined effect of SiO2 additive for membrane and catalyst layer on the performance of the PEFCs using diethylmethylammonium trifluoromethanesulfonate ([dema][TfO])/sulfonated polyimide (SPI) electrolytes to evaluate RTMS/SPI/solid acid system for PEFCs. The addition of SiO2 in the membrane and anode catalyst layer improved cell activity of catalyst layer, ionic conductivity and stabilize the cell performance against gas flow rate increase.These effects would be affected by the behavior of produced water.
FTIR Analysis of the State of Water in Radiation Grafted ETFE Anion Exchange Membrane for Fuel Cell Applications
Authors: Pandey Tara Prasad , Liberatore Matthew W , Herring Andrew M
Published: October 2013

Infrared study of water in a poly(ethylene-co-tetrafuloroethylene) anion exchange membrane at different level of hydration (%RH 0, 25, 50, 75 and 100) was performed using a Fourier transform infrared (FTIR) microscope. FTIR spectra showed at least two different states of water present in the membrane. The presence of both the non-hydrogen bonded water molecules at the lower hydration level and the hydrogen bonded water molecules at the higher hydration level, unambiguously, are altered with changing humidity.
Assessing the Limits of Water Management Using Asymmetric Micro-Porous Layer Configurations
Authors: Ashraf Gandomi Yasser , Mench Mathew M.
Published: October 2013

In high-power polymer electrolyte fuel cell systems, prevention of anode dry-out through enhanced back flux of water and restriction of evaporative losses is needed. One potential method to engineer the back flux of water to the anode is to utilize an asymmetric anode and cathode micro-porous layer configuration to independently tailor anode and cathode thermal and mass transport resistances. Extensive experimental tests have been performed to study the impact of asymmetric MPL configuration on the net water drag coefficient using sets of MPL with different thermal and mass transport resistances. It was observed that with asymmetric MPL alignment between the anode and cathode, the net water drag coefficient could be significantly altered, opening the door to enhanced high power performance at anode-dryout conditions.
Surface Analytical Methods for the Development of Electrochemical Components of Polymer Electrolyte Fuel Cells
Authors: Biswas Indro , Gazdzicki Pawel , Schulze Mathias
Published: October 2013

A comprehensive overview of infrared absorption, Raman, and X-ray photoemission spectroscopy and their application in fuel cell research is given in this paper. Based on these ex-situ spectroscopic techniques a set of methods addressing the specific problems in the development of polymer electrolyte fuel cells are discussed and compared, regarding multi scale chemical characterizations and the analytics of outer surfaces, inner surfaces and buried layers. It is shown, that a combination of complementary methods is necessary to gather a comprehensive view of the occurring processes and mechanisms.
Investigation of Influence of Pt Oxidation State on Carbon Surface Oxidation in PEMFC Cathode Electrode
Authors: Takeuchi Norimtisu , Kumei Hideyuki , Yoshida Toshihiko
Published: October 2013

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.
Microstructure and Performance of Catalyst Layer Based on Highly Graphitized Carbon Support
Authors: Song Jung-min , Kim Hee-tak , Park Yong-bum , Song Ka-young , Kim Yeon-su , Lee Sung-chul , Kong Nak-won , Kim Tae-yoon , Yoshida Yasuki , Pak Chanho
Published: October 2013

We have found that use of a highly graphitized carbon as a catalyst support leads to the loss of power performance at low humidity even though voltage holding durability is greatly improved. This finding motivates current study of the influence of carbon support on microscopic distribution of ionomer and power performance. Electrochemical analysis for the MEAs prepared with a highly graphitized carbon and an amorphous carbon reveals that the ionomer coverage is greatly influenced by the nature of the carbon. The high surface area carbon gives higher ionomer coverage than the highly graphitized carbon. The investigation of pore structure of catalyst layers show that the primary pore of all catalyst layers is hardly filled with ionomer, suggesting that there is still room to increase the catalyst utilization. The water adsorption experiment for various Pt/C and PtCo/C indicates that water preferentially locates on Pt and PtCo surface rather than carbon.
Improving ORR Activity of Group 4 and 5 Metal Oxide-Based Cathodes for PEFCs
Authors: Ishihara Akimitsu , Yin Shihong , Suito Kazuaki , Uehara Naoki , Okada Yohei , Kohno Yuji , Matsuzawa Koichi , Mitsushima Shigenori , Chisaka Mitsuharu , Ohgi Yoshiro , Matsumoto Masashi , Imai Hideto , Ota Ken-ichiro
Published: October 2013

In order to develop a non-precious metal cathode for PEFCs, we have tried to improving oxygen reduction activity of Zr oxide-based cathodes. We succeeded to prepare Zr oxide-based cathodes with fine primary particles using zirconium oxy-phthalocyanine as a starting material. However, secondary particle size was very large, resulting that the activity was insufficient. Therefore, we performed ball mill to crack secondary particles for increasing the actual surface area. In addition, nitridation of oxide-based compounds was performed to increase the active sites for oxygen reduction reaction such as oxygen defects and/or nitrogen atoms including oxide lattice.
Electrochemical Oxygen Reduction on Metal-Free Nitrogen-Doped Graphene Foam in Acidic Media
Authors: Liu Jianfeng , Sasaki Kazunari , Lyth Stephen Matthew
Published: October 2013

Non-precious oxygen reduction reaction (ORR) catalysts could help reduce the cost of future generations of polymer electrolyte membrane fuel cells (PEFCs). One class of Pt-free catalysts for PEFCs are nanostructured Fe/C/N-based materials. In these, the nature of the active site is still hotly contested. Resolving this issue could lead to the development of better catalysts. One approach to achieve this is to study nitrogen-doped carbons which do not contain any Fe. Such materials have been studied, but largely in alkaline media where high activity is obtained. To truly understand the ORR mechanism of Fe/C/N-based catalysts, measurements in acid media are required to simulate the activity in proton-based PEFC systems. Here we present bulk synthesis of a metal-free nitrogen-doped graphene powder with remarkable surface area. We apply this as an ORR catalyst in acid media and comment on the reaction mechanism.
Best Practices for Examining Anion Exchange Membrane Alkaline Stability for Solid-State Alkaline Fuel Cells
Authors: Arges Christopher George , Wang Lihui , Parrondo Javier , Ramani Vijay K.
Published: October 2013

Alkaline fuel cells (AFCs) with an anion exchange membrane (AEM) electrolyte are promising electrochemical energy conversion devices since they can operate without platinum group metals. In the past decade, AEMAFC performance has improved substantially due to improvements in electrode binders and AEM ionic conductivity. However, the alkaline (in)stability of AEMs is a significant hurdle that precludes commercialization of this technology. To date, there have not been any satisfactory strategies to adequately assess an AEM’s suitability for an AFC. Here, we report a best practices approach to evaluate a leading AEM candidate (poly(2,6-dimethyl 1,4-phenylene) oxide (PPO) with quaternary ammonium groups) for AEMAFCs. In this work, PPO AEMs were immersed in alkaline solutions at elevated temperatures and were characterized via functional tests (ion-exchange capacity and mechanical properties) and via two-dimensional NMR techniques. The data generated from these tests provided mechanistic insights into the degradation of PPO AEMs in alkaline conditions.
Segmentation of Polymer Electrolyte Fuel Cell (PEFC) With sub–millimeter Resolution in the Land-Channel Direction
Authors: Shrivastava Udit N , Tajiri Kazuya
Published: October 2013

The interaction between the flow channels and gas diffusion layer affects the water management and the thermal management. Consequently, the land-channel geometry in a typical PEFC influences the uniformity of current generation in the land-channel direction. Therefore it becomes important to assess the current density distribution along the land-channel direction. This work is focused on developing a segmented PEFC to measure the current density in the land and the channel areas at sub-millimeter resolution. Design criteria pertaining to the segmented PEFC are explained in detail. By paying attention to those criteria, a new design and fabrication method to develop a segmented PEFC to measure current density at sub-millimeter resolution are proposed. Ex-situ experiments are conducted to validate the design, and in-situ tests are performed to obtain the current density distribution under the land and the channel areas in dry and wet condition.
Advanced Durability Tests for High Temperature PEM Fuel Cells
Authors: Jeon Yukwon , Hwang Hyung-Kwon , Park Jeongho , Jeon So-Me , Shul Yong-gun
Published: October 2013

Durability has been considered a fundamental issue for commercialization of polymer electrolyte membrane fuel cell (PEMFC). Especially, recent developments have tended to focus on the PEMFC operating at high temperature range (>120℃) and low relative humidity (<40% RH) because of simplified system and high efficiency. In this study, advanced protocols for durability test based on degradation of high temperature PEMFC are developed, which include accelerated life time (ALT) test to save the time as well as cost. The ALT durability test is compared with the general constant (0.6V) mode test to investigate the different degradation behavior. The electrochemical analyses of membrane electrode assembly (MEA) were confirmed by polarization curve and impedance spectroscopy.
New Approach to High-Efficiency Non-PGM Catalysts Using Rationally Designed Porous Organic Polymers
Authors: Yuan Shengwen , Goenaga Gabriel , Grabstanowicz Lauren , Shui Jianglan , Chen Chen , Commet Sean , Reprogle B. , Liu Di-Jia
Published: October 2013

To replace the current Pt/C catalyst with low- or non-PGM materials represents a critical technology challenge for commercialization of the proton exchange membrane fuel cell. To compete with the precious metal based catalyst, the non-PGM material must have higher active site density and improved turn-over-frequency. In this report, we discuss a new method of preparing “support-free” non-PGM catalysts produced by using the transition metal decorated porous organic polymers as precursors. The new approach has led to formation of catalysts with high efficiency towards the oxygen reduction reaction, tested in the oxygen saturated acidic electrolyte and under actual fuel cell operating condition.
Rotating Ring-Disk Study of Metal-Nitrogen-Carbon Catalyst Prepared by High Pressure Pyrolysis
Authors: Leonard Nathaniel , Ganesan Selvarani , Calabrese Barton Scott
Published: October 2013

Low-cost oxygen reduction catalysts composed of pyrolyzed metal/nitrogen/carbon (MNC) compounds involve the association of metal and nitrogen species integrated into a conductive carbon support. The present work considers peroxide generation: an analysis of rotating ring-disk electrode studies sheds further light on the oxygen reduction mechanism of MNC catalysts. Oxygen reduction proceeds primarily through a complete four-electron pathway to water without a desorbing intermediate.
Corrosion Study of Mesoporous Carbon Supports for Use in PEM Fuel Cells
Authors: Forouzandeh Farisa , Banham Dustin , Feng Fangxia , Li Xiaoan , Ye Siyu , Birss Viola
Published: October 2013

In this study, the corrosion resistance of two ordered, high surface area, mesoporous carbons (OMCs) were evaluated for PEM fuel cell applications, in comparison with microporous Vulcan carbon (VC). Using a hexagonal mesoporous silica as a hard template, the OMCs were synthesized using sucrose and anthracene as the carbon precursors, denoted as OMC-S and OMC-A, respectively. The corrosion testing protocol involved a potential cycling-step sequence between 1.4 V for 50 s and 0.8 V for 10 s, for a total of 18 cycles, all in room temperature 0.5 M H2SO4. The corrosion resistance of the carbons is found to be VC > OMC-A > OMC-S, which correlates with their degree of graphitization, as determined by X-ray diffraction and thermogravimetric analysis.
Durable and Water Manageable Ordered Mesoporous Supports for Polymer Electrolyte Fuel Cells
Authors: Hwang Sun-Mi , Lee Sehui , Sohn Young-Jun , Yang Tae-Hyun , Park Gu-Gon
Published: October 2013

The enhancement of durability is one of the challenges to be resolved for the commercialization of polymer electrolyte fuel cells (PEFCs). One of the major reasons for the degradation of cell performance is an improper management of water produced by oxygen reduction reaction (ORR) at the cathode. In this study, we focus on durable and water manageable electrocatalyst supports through the modification of the pore structures.