bluuebunny/crossref_metadata_2025 huggingface dataset:
Oscillation of PEFC under Low Cathode Humidification: Effect of Gravitation and Bipolar Plate Design
Authors: Sanchez Daniel G , Ortiz Alfredo , Friedrich K.Andreas
Published: October 2013

Oscillatory fluctuations of a single proton exchange membrane fuel cell appear upon operation with a dry cathode air supply and a fully humidified anode stream. Periodic transitions between a low- and high-current operation point of the oscillating state due to the balance of drying and wetting processes in combination with water transport have been observed previously; however, several new aspects have been investigated in the present study, providing insight into the initiation processes. The oscillations are caused by periodic flow type changes from one- to two-phase flow in the anodic channels of the flow field. It has been observed that cell orientation with respect to Earth’s gravity field affects the liquid water distribution in the anodic flow channels and, thus, also affects the oscillatory behavior of the cell performance.
A High Energy Density System by Thin Metallic Bipolar Plates
Authors: Bates Alex , Mukherjee Santanu , Lee Sang C. , Kwon Osung , Ha SungMok , Thomas Sobi , Lee D. H. , Park Sam
Published: October 2013

A fuel cell in development for use in unmanned aerial vehicles is simulated and presented. The fuel primarily cell tackles the issue of weight for unmanned aerial vehicle applications. The balance of plant is also significantly reduced by this fuel cell which reduces weight and makes the fuel cell system more compact. Simulations include fluid flow, electrochemical effects, concentrated species transport, and heat distribution. The polarization plot produced by the simulation is in good agreement with experimental results.
Non-Crosslinked Perfluoro-Polymer Electrolytes with Two Acid Groups and Their Properties
Authors: Shinohara Akihiro , Kudo Kenji , Kawasumi Masaya , Morimoto Yu , Hasegawa Naoki
Published: October 2013

Non-crosslinked perfluoro electrolytes with two acid groups at the same saide chains were synthesized. The reaction of C3Rf (Rf = OH, NHSO2CF3, and NHSO2(CF2)3CF3) with sulfonamidated Nafion ending in the functional SO2NH2 groups afforded non-crosslinked electrolytes. These electrolytes showed higher water uptakes than that of Nafion. The proton conductivity of NB-CO (Rf = OH) under dry condition is three times as high as that of Nafion. Although the proton conductivity of NB-C4 (Rf = NHSO2(CF2)3CF3) decreases compared with NB-C0, the gas permeability is higher than those of NB-C0 and Nafion
A Revised EVB Model for Proton Transport in Hydrated Nafion Membrane
Authors: Mabuchi Takuya , Tokumasu Takashi
Published: October 2013

We have performed an atomistic analysis of transport phenomena of hydronium ions and water molecules in the hydrated Nafion membrane. The new empirical valence bond (EVB) model is developed based on the previous study of EVB model reported by Walbran et al. in order to improve the description of proton mobility in both aqueous and Nafion environments. We have calculated mean square displacement (MSD) to determine diffusion coefficients of hydronium ions and water molecules as a function of hydration level for the investigation of the impact of Grotthuss mechanism on the transport property of solvent molecules as well as the validation of our simulation by comparing with the experimental data of diffusion coefficients. A large contribution of Grotthuss mechanism for the diffusion of hydronium ions has been found at high water contents, testifying the important impact of Grotthuss mechanism in the membrane as well as in the bulk aqueous solutions.
Optimization of Fuel Cell Generation Environment by Observation of Water Using Neutron Radiography
Authors: Iwasawa Chikara , Chiba Hiroto
Published: October 2013

Electric generation by a polymer electrolyte fuel cell requires water to help ensure proton conductivity of the membrane electrode assembly (MEA). However, excess water in the channels and the diffusion layer can impede gas supply, so it becomes important to observe water and control it. This study used neutron radiography to observe the state of the water that accumulated during power generation in a fuel cell of a size in actual use. Observations were performed from the two directions of the through-plane direction and the in-plane direction. The results helped to clarify the mechanism by which water accumulates and the correlation between the accumulated water and voltage behavior. In terms of practical use, the optimum electric generation environment was set in terms of water and electric generation performance, and applied to the control of an actual vehicle.
Catalyst Poisoning Property of Sulfonimide Acid Ionomer on Pt (111) Surface
Authors: Kodama Kensaku , Shinohara Akihiro , Hasegawa Naoki , Shinozaki Kazuma , Jinnouchi Ryosuke , Suzuki Takahisa , Hatanaka Tatsuya , Morimoto Yu
Published: October 2013

A thin film of a novel ionomer, NBC4, which has two sulfonimide acid groups in its side chain ended with a hydrophobic group, instead of sulfonic acid groups, was formed on a Pt (111) surface and its catalyst poisoning property was compared with that of Nafion, which has sulfonic acid groups. For NBC4, anionic poisoning is weaker and oxygen reduction reaction activity is higher by ca. 30% below 0.86 V vs the reversible hydrogen electrode than for Nafion.
Nanofiber Fuel Cell Electrodes I. Fabrication and Performance with Commercial Pt/C Catalysts
Authors: Brodt Matthew , Wycisk Ryszard , Pintauro Peter N. , Han Taehee , Dale Nilesh , Adjemian Kev
Published: October 2013

Nanofiber electrodes prepared with three different commercial Pt/C catalysts and 1100 EW Nafion® binder were fabricated by electrospinning. The electrodes were further processed into membrane-electrode-assemblies (MEAs) using Nafion 211 as the membrane material. MEAs were evaluated for catalyst activity and power output in a hydrogen/air fuel cell at 80oC. Tanaka Kikinzoku Kogyo (TKK) TEC10E50E (46.1% Pt on Ketjen Black) was more electrochemically active and produced slightly more power than its heat-treated counterpart, TKK TEC10E50E-HT (50.5% Pt on Ketjen Black), and Johnson Matthey HiSpec 4000 catalyst (40% Pt on Vulcan carbon). The nanofiber cathodes were compared to MEAs with standard non-structured gas diffusion electrodes (GDEs) containing the same catalysts, and in all cases, the electrospun fibers generated more power. For example, with a Pt loading of 0.10 mg/cm2, the electrospun TKK TEC10E50E generated 470 mW/cm2 at a 0.65 V vs. 349 mW/cm2 for the GDE-based MEA, an improvement of 35%. The effect of nanofiber composition (the ratio of Pt/C to Nafion) and the effect of fiber diameter on power output were also investigated. In general, such changes had a little or no impact on performance and all the electrospun mats tested yielded MEAs that produced very high power.
Investigation of PEFC Freeze Start by X-ray Tomographic Microscopy
Authors: Roth Jörg , Zurbrügg Mark Rene , Irvine Sarah , Marone Federica , Stampanoni Marco , Büchi Felix N.
Published: October 2013

Starting from subfreezing temperatures presents a challenge for PEFC since ice may form in the gas flow channel, gas diffusion layer and catalyst layer and restrict the gas transport. Under non-isothermal conditions, a start-up is successful if the cell temperature rises above 0°C before freezing occurs. Under isothermal conditions below 0°C cells operate for a certain time followed by a sudden drop in power. The distribution of liquid/solid water during an isothermal start at subfreezing temperatures is quantitatively mapped by means of X-ray tomographic microscopy to improve understanding the circumstances at the phase transition and its effects on gas diffusion. Evidence was found that the produced water is in supercooled state at -10 °C initially and the drop of power is associated with freezing of the water in the cell at a GDL saturation of 20 to 30%.
STXM Characterization of Nanostructured Thin Film Anode Before and After Start-Up Shutdown and Reversal Tests
Authors: Lee Vincent , Susac Darija , Kundu Sumit , Berejnov Viatcheslav , Atanasoski Radoslav T , Hitchcock Adam P , Stumper Juergen
Published: October 2013

Nanostructured thin film (NSTF) catalysts are promising for proton exchange membrane fuel cell applications. We have used synchrotron based scanning transmission soft X-ray microscopy (STXM) to evaluate composition and structure of NSTF anodes prepared by decaling and the changes that occur after start-up shut-down and reversal testing. We find the metal decorated perylene red support material is mechanically compressed, so that there is very little penetration of the catalyst into the membrane. Such a structure exhibits little or no chemical modification upon generating the PEM-FC structure. In contrast, after the testing there is essentially no perylene red material detected. However, there is no evidence that the loss of the perylene red support affects the catalytic properties of the anode NSTF structure.
PEMFC Cathode Contamination Mechanisms for Several VOCs - Acetonitrile, Acetylene, Bromomethane, Iso-Propanol, Methyl Methacrylate, Naphthalene and Propene
Authors: St-Pierre Jean , Ge Junjie , Zhai Yunfeng , Reshetenko Tatyana V. , Angelo Michael
Published: October 2013

The behavior of PEMFCs exposed to airborne contaminants was characterized in 2 stages. In the first stage, impedance spectroscopy was used to identify resistance loss types. In the second stage, other ex situ and in situ characterization methods were employed to obtain more detailed information about observed resistance loss types: rotating ring/disc electrode, membrane conductivity cell, tracer based method for residence time distribution measurements, segmented cell, and fuel cell coupled with a gas chromatograph/mass spectrograph. All 7 VOCs led to kinetic and mass transfer resistance changes. Only acetonitrile led to an ohmic resistance change. A decrease in catalyst active area (7 to >90 %) and increase in H2O2 side reaction product (18 to 1027 %) accounts for the smaller oxygen reduction current (12 to 100 %). An acetonitrile decomposition product is presumed to be responsible for the observed in situ ohmic loss because acetonitrile did not show an effect in the conductivity cell. Modest current redistributions were noted (<19 % on an absolute and dimensionless basis) but acetylene also initially showed a strong transient effect (≤100 % on an absolute and dimensionless basis) attributed to a gradual contamination along the flow field length. Only the unaffected contaminant species, CO2 and CO were detected at the cathode outlet. Contaminant conversion increased at higher cell voltages (62 to 332 % V-1) indicative of electrochemical oxidation. An acetylene contamination mechanism is proposed.
Effect of Ca2+ as an Air Impurity on Polymer Electrolyte Fuel Cells
Authors: Wang Xiaofeng , Qi Jing , Ozdemir Ozan , Pasaogullari Ugur , Bonville Leonard J. , Molter Trent
Published: October 2013

Cationic contamination is a well-known phenomenon that causes performance degradation and decrease in lifetime in polymer electrolyte based electrochemical systems. Calcium is a significant cationic impurity due to its prevalence. In this work, the role of calcium is investigated in-situ by injecting into the cathode of a single polymer electrolyte fuel cell (PEFC) through a nebulizer as a solution of calcium sulphate (CaSO4) in deionized (DI) water. Stability tests are conducted to determine the contaminant effects at different current densities with different Ca2+ concentrations. It is found that 5 ppm Ca2+ in air at 1 A/cm2 is high enough to lead to high cell performance loss as well as severe membrane degradation. Chemical precipitation is found at the contact regions between the gas diffusion layer (GDL) and flow plate of the cathode at all test conditions.
Effect of Cationic Contaminants on Polymer Electrolyte Fuel Cell Performance
Authors: Qi Jing , Wang Xiaofeng , Ozdemir Ozan , Uddin Md. Aman , Bonville Leonard J. , Pasaogullari Ugur , Molter Trent
Published: October 2013

The effect of the in-situ injection of cationic contaminants on polymer electrolyte fuel cell (PEFC) performance is investigated. Four foreign cations (Ba2+, Ca2+, Al3+, K+) were chosen as contaminants in this study due to their prevalence and chemical structure (e.g. valence). It is found that the cells with Ba(ClO4)2 and Ca(ClO4)2 injection exhibited little cell voltage change during a current hold test, and the cells with Al(ClO4)3 and KClO4 injection showed a larger cell performance change with decreasing cell voltage and increasing cell resistance. After recovery tests by switching back to DI water from the cation injection, the cells which were contaminated with Ba(ClO4)2 and Ca(ClO4)2 had a tendency to recover portion of the lost performance; however, the cells with Al(ClO4)3 and KClO4 injection did not recover even though the contaminant injection time is shorter than that of the above two cells.
Effects of Chloride Contamination on PEFCs
Authors: Uddin Md. Aman , Wang Xiaofeng , Qi Jing , Ozdemir M. Ozan , Bonville Leonard J. , Pasaogullari Ugur , Molter Trent
Published: October 2013

The performance and durability of PEFCs were investigated by introducing HCl and five different chloride salts into the air stream of an operating fuel cell. Under the same operating conditions and at a constant 28.5 mM chloride (Cl-) concentration, cell performance degradation can be ranked as HCl> AlCl3 > FeCl3 > CrCl3 > NiCl2, MgCl2. Water evaporation in the flow field surface was found to be causing precipitation of chloride salts. At lower RH, water content decreased and salt deposits completely blocked some of flow channels and caused death of the fuel cell. Moreover, contaminants crossed the GDL, reached the CCM surface, and caused significant performance drop.
Dealloying of Pt Bimetallic Catalysts at Constant Electrode Potentials
Authors: Rudi Stefan , Gan Lin , Cui Chunhua , Strasser Peter
Published: October 2013

We present the synthesis and controlled dealloying of homogeneously alloyed well-dispersed PtNi3 nanoparticles. This material was studied by dealloying at various constant potentials for 24 hours in order to investigate structural changes as function of electrode potentials. Using electrochemical analysis techniques we have provided evidence that the structure and composition of the dealloyed nanoparticles depended sensitively on the applied electrode potential, yet, surprisingly were also influenced by the presence or absence of adsorbed surface species such as hydrogen or oxygenates. Based on this finding, new dealloying strategies could be designed in order to enhance the catalytic activity and stability toward the oxygen reduction reaction (ORR).
Separation Analysis of Electro-Osmosis and Diffusion of Water in Electrolyte Membrane of PEMFC under Low-Humidity Operation
Authors: Nishida Kosuke , Hosotani Takuto , Asa Masaya , Tsushima Shohji , Hirai Shuichiro
Published: October 2013

To alleviate performance degradation of proton exchange membrane fuel cell (PEMFC) due to membrane dehydration during low-humidity operation, it is essential to understand and control water transports through electrolyte membrane. In this study, the water vapor and current distributions on the anode side of a PEMFC was firstly measured by using the effective visualization tool proposed in our previous work, and the net water transport coefficient was quantitatively estimated under low-humidity conditions. Furthermore, the electro-osmotic drag (EOD) coefficient of Nafion membrane was also measured based on hydrogen pumping method. Therefore, the electro-osmosis and back-diffusion of water through the electrolyte membrane in the operating PEMFC can be separately analyzed. Results revealed that the cathode inlet humidification promotes the back-diffusion of water rather than the electro-osmotic flow, and prevents the membrane dryout.
High Catalytic Activity for Glycerol Electrooxidation by Binary Pd-Based Nanoparticles in Alkaline Media
Authors: Palma Livia Martins , Almeida Thiago Santos , De Andrade Adalgisa Rodrigues
Published: October 2013

Glycerol is a nonflammable and volatile compound obtained from biodiesel production, it has good theoretical energy density (5.0 kWh kg-1). Complete glycerol oxidation to CO2 in acid medium is difficult to achieve, but alkaline medium facilitates this process. Pd is a promising catalyst for alkaline medium, however, it requires co-catalysts, to enhance the oxidation process. In this paper, we investigated glycerol oxidation using catalysts supported on carbon containing 40 wt% PdM/C metal loading (M = Ru, Ni, Sn, Mn, Fe) and microwave-assisted heating. We recorded cyclic voltammetric and chronoamperometric curves in the presence and absence of glycerol, in alkaline medium (1.0 mol L-1 NaOH). PdM/C catalysts underwent the characteristic metal transition to Pd-hydroxide and Pd-oxide on the carbon support. Pd71Ru29/C was the best catalyst for glycerol oxidation; it contains particles measuring between 2 and 7 nm. In conclusion, catalysts containing a mixture of phases in the crystalline structure afford high glycerol oxidation yields.
Impact of Structural Plastics as Balance of Plant Components on Proton Exchange Membrane Fuel Cell Performance
Authors: Yu Paul Taichiang , Bonn Eric A. , Lakshmanan Balsu
Published: October 2013

The impact of plastic material (Polyamide 610) as a balance of plant component on PEMFC (Proton Exchange Membrane Fuel Cell) performance was investigated in this paper. It is shown that this plastic material leaches out anions (chloride and nitrate) and cations (silicon and sodium) and low molecular weight compounds (polyamide 610 cyclic dimer and caprolactam) after 6 weeks of soaking time. The leachants result in significant loss of available Pt sites and decrease of membrane conductivity. The infusion test results show that the cell voltage loss decreases linearly with increased Pt loading while it increases linearly with increased leachant concentration. Increase of temperature also increases cell voltage loss. Although, the cell performance successfully recovers ~61%, the loss still does not meet strict automotive durability targets. Various types of plastic materials are being screened in order to minimize the adverse impact on fuel cell performance.
Electrochemical Characterization of Hydrogen Pump with Internal Humidifier and Dead-End Anode Channel
Authors: Ito Kohei , Hao Yan Ming , Nakajima Hironori , Yoshizumi Hiroshi , Sasaki Kazunari
Published: October 2013

Hydrogen gas is compressed with a new electrochemical pump, where internal humidifier is built in, and dead-end at anode is considered for a practical situation. Both the voltage and current efficiency of the hydrogen pump is evaluated experimentally. The pump is operated up to 2 MPa under the temperature condition of 293 and 333 K. The voltage efficiency indicates nearly 50% at most and the current efficiency is over 90%. Overpotentials inherently involved in the pump are discussed with electrochemical impedance spectroscopy.
Templated Non Precious Cathode Catalysts Prepared by Transition Metal and Poly(ethyleneimine) for Oxygen Reduction Reaction in Alkaline Electrolyte
Authors: Shi Jingjing , Xu Pang , Zheng Mingfu , Liu Yuyu , Qiao Jinli
Published: October 2013

The present paper is devoted to preparation and characterization of catalyst for oxygen reduction reactrion (ORR) based on pyrolyzed metal-poly(ethyleneimine)(namely M-PEI, M=Co, Fe, Ce). Template method was applied to obtain catalyst with high surface area and porosity. Results of electrochemical characterization, which was performed using cyclic voltammetry (CV) and linear sweep voltammetry (LSV) employing a rotating disk electrode (RDE), with emphasis on the activity of the catalyst are presented. The catalytic activity was found to depend strongly on the kind of transition metal and anion species. The relation of eletrocatalytic activity varies as follows: Co > Fe > Ce for transition metals and, nitrate > sulfate for anion species. Co-PEI, with onset potential at 0.1V, half-wave potential at 0V and average transferred electron number at 3.3, was found to show the highest ORR activity among the catalysts studied.
Manufacturing and Stabilization of PtCo/C Cocatalysts for PEM Fuel Cells
Authors: Grimmer Christoph , Schenk Alexander , Pichler Birgit Elvira , Perchthaler Markus , Hacker Viktor
Published: October 2013

High manufacturing costs of active layers of polymer electrolyte fuel cells (PEMFCs) are a major challenge for this promising technology to penetrate the market. In this report a new, straightforward and easily scalable manufacturing process of platinum cobalt cocatalysts is described and demonstrated on a lab-scale. The stability issue of this kind of materials is counteracted by post-preparation treatments, which are also designed in order to be feasible on a big scale. All catalysts are characterized by means of cyclic voltammetry in acidic as well as alkaline electrolyte and rotating disk electrode experiments. The catalysts’ stability is estimated by accelerated stress tests.
NMR Investigation of Water Diffusion in a Nafion Membrane under Traction
Authors: Perrin Jean-Christophe , Klein Mathieu , Leclerc Sébastien , Guendouz Laouès , Dillet Jérôme , Lottin Olivier
Published: October 2013

Surface NMR probes are appropriate for the study of water properties in thin films as they offer a high signal to noise ratio. Using a new methodology that combines the use of a surface probe and a mini traction machine we performed water self-diffusion measurements in a unique Nafion membrane under traction. We observe that the diffusion anisotropy, correlated to the imposed order in the membrane, is much higher than in a stack of stretched / released samples hydrated at similar water content. The same approach can be used to study membranes under compression.
Design and Modeling of High Temperature Water Free Proton Exchange Membranes in DEA PEMFC Operations
Authors: Şanli Lale , Alkan Gursel Selmiye , Yesilyurt Serhat
Published: October 2013

Polymer electrolyte membrane fuel cell (PEMFC) is a greatalternative in transportation however there are still some issues onthe application of PEMFC, such as complexity in balance-of-plantdesign and cost of the system. Dead ended anode (sealed offanode) design might be a solution to reduce the complexity ofPEMFC. DEA operation eliminates the expensive hardware, suchas mass flow controllers, hydrogen recovery system andhumidifiers of PEMFC system. Moreover, the DEA operation ofNafion® is experiencing the disadvantages of low operationtemperature (40-80 °C) as the corrosion of the expensiveelectrodes by accumulated water. Beyond it is low operationtemperatures; Nafion® is also expensive and increases the cost ofthe PEMFC. Hence, in this study, the water free, high temperatureand cost competitive radiation induced grafted membranes weresynthesized and tested in both flow through anode (FTA) and deadended anode (DEA) operation in PEMFC.
Characterization and Performance of Catalyst Layers Prepared by Inkjet Printing Technology
Authors: Saha Madhu S , Tam Mickey , Berejnov Viatcheslav , Susac Darija , McDermid Scott , Hitchcock Adam P , Stumper Jürgen
Published: October 2013

The relationship between the structure of cathode catalyst layers (CCLs) prepared by different coating techniques and fuel cell performance was investigated. Inkjet printing technique was employed for producing CCLs directly on Nafion membranes, while Mayar bar was used to prepare conventional CCL coating that was decaled-transferred on to the membrane. Scanning transmission X-ray microscopy was used to determine the ionomer and carbon support distributions within the interior of both CCL structures. Distinctly different ionomer distributions were observed impacting Pt- utilization.
Design of Experiments to Evaluate Material Characteristics of Porous Transport Layers in Polymer Electrolyte Membrane Fuel Cells
Authors: Flick Sarah , Mérida Walter
Published: October 2013

Designed experiments using statistical methods enable an efficient and economic experimental approach that can account for factor interaction. This work employs a two-level split-plot design to study the influence of material characteristics of the gas diffusion layer (GDL) in polymer electrolyte membrane fuel cells (PEMFC). The factors used in this design included six operating parameters (anode stoichiometry, cathode stoichiometry, temperature, anode inlet relative humidity and cathode inlet relative humidity and gas pressure) and a categoric factor (“Type of GDL”). At each test point, a voltage response was measured under galvanostatic conditions at 1.0 A/cm2. The results show a good fit of the model based on predicted results and residuals. The analysis demonstrates design of experiment methods to be an adequate tool for evaluating the influence of the tested GDL materials.
Measurement Technique of Oxygen Diffusion Resistance through Gas Diffusion Layer
Authors: Ohira Hironori , Kikuchi Katsuhide , Ida Atsushi , Tomiyasu Joji , Yamamoto Atsushi
Published: October 2013

It is important to measure the oxygen diffusion resistance of both gas diffusion layers (GDLs) and catalyst layers (CLs) to improve the performance of polymer electrolyte fuel cells. In this study, we develop a technique to measure oxygen diffusion resistance with high precision. The technique uses an oxygen sensor and zinc-air batteries, which enhance the oxygen concentration gradient. Using this technique, the oxygen diffusion resistances of two GDLs with microporous layers (MPLs) with different porosity are measured. Experimental results show that the oxygen diffusion resistance of GDLs with a MPL decreases as the porosity of the MPL increases.
Degradation of Gas Diffusion Layers in PEM Fuel Cells during Drive Cycle Operation
Authors: Mukundan Rangachary , Davey John R. , Rau Karen , Langlois David A. , Spernjak Dusan , Fairweather Joseph D. , Artyushkova Kateryna , Schweiss Ruediger , Borup Rod L
Published: October 2013

Polymer electrolyte membrane (PEM) fuel cells show voltage degradation when subjected to long-term drive cycle operation. While the kinetic losses in the fuel cells can be assigned to catalyst layer degradation, there is a significant mass transport loss of up to 100mV at 2 A/cm2 in 400 hours of operation. This mass transport loss can be attributed to the Gas Diffusion Layer (GDL) degradation especially when using low surface area carbon based catalyst materials. Ex situ ageing studies where the GDL is oxidized in a peroxide solution seem to simulate this degradation mechanism in terms of both the increase in graphitic carbon and surface-oxide species. The ex situ aged GDLs result in similar voltage losses when operated with fresh membrane-electrode assemblies (MEAs). AC impedance results confirm that these losses are due to mass transport limitations, probably arising from loss of hydrophobicity of the GDL material. To alleviate these mass transport losses, various combinations of materials have been examined; improved performance under drive cycle operation was obtained with a GDL material that had carbon nano-tubes in the MPL.
Pt3Co Nanoparticles and Carbon to the Test of PEMFC Operation
Authors: Lopez-Haro Miguel , Dubau Laetitia , Castanheira Luis , Durst Julien , Chatenet Marian , Bayle-Guillemaud Pascale , Guétaz Laure , Maillard Frederic
Published: October 2013

This study shows that the modifications in structure and composition of Pt3Co/C nanoparticles during real life PEMFC operation (3422 hours of operation at T = 70 °C under H2/air) is much richer than previously thought from accelerated stress tests. Using aberration-corrected scanning transmission electron microscopy and electron energy-loss spectroscopy, we show that Co atoms are continuously dissolved from the mother electrocatalyst, and that three different metal nanostructures emerge during PEMFC operation: (i) Pt-Co/C core-shell nanoparticles characterized by an alloyed core surrounded by a thick Pt-rich shell, (ii) Pt-Co/C “hollow” nanoparticles and (iii) pure Pt/C “hollow” nanoparticles, from which Co dissolution has been completed. The high surface area carbon support is not stable either, its less organized domains being preferentially corroded, a fast kinetics process that is followed by slower corrosion of its graphitic regions.
PEM Fuel Cell Catalyst Layer Structure Degradation during Carbon Corrosion
Authors: Borup Rod L , Mukundan Rangachary , Fairweather Joseph D. , Spernjak Dusan , Langlois David A. , Davey John R. , More Karren L. , Artyushkova Kateryna
Published: October 2013

One of the major degradation involves the electrocatalyst, including the corrosion of the carbons used as catalyst supports which leads to changes in the catalyst layer structure. These changes in the catalyst layer structure lead to reduced kinetics and to mass transport limitations. The catalyst layer degradation is due to a combination of degradation mechanisms, including localized effects and depends upon operating conditions
Influence of Platinum Precipitation on Properties and Degradation of Nafion® Membranes
Authors: Helmly Stefan , Ohnmacht Benjamin , Hiesgen Renate , Gülzow Erich , Friedrich K.Andreas
Published: October 2013

In this study, the role of Pt concentration and distribution in the membrane on ionomer degradation was investigated. Nafion® membranes were impregnated with different mass fraction of Pt via ion-exchange and operated as membrane electrode assemblies (MEAs) at open circuit voltage (OCV). Various MEAs with known Pt concentration were characterized by electrochemical in-situ measurements regarding both, membrane properties and ionomer degradation. Additionally, Pt particle distribution in the membrane cross sections was analyzed. The presence of Pt precipitations was found to influence ionic conductivity and the sensitivity of cell performance for humidification. Ionomer decomposition increased with concentration and surface area of Pt deposits as well as distance between particles. The comparison between Pt precipitated artificially and during operation showed a considerable difference in particle distribution and extent of internal membrane humidification due to water formation at Pt sites.
Structurally Tuned Nitrogen Doped Cerium Oxide as a Superior Free Radical Scavenger for Mitigating Polymer Electrolyte Membrane Degradation
Authors: Prabhakaran Venkateshkumar , Ramani Vijay K.
Published: October 2013

Commercial cerium oxide (CeO2) and as-prepared high-surface-area CeO2 (220 m2/g) were doped with nitrogen and the ROS (reactive oxygen species ) scavenging efficacy of the samples was evaluated using in-situ fluorescence spectroscopy. Changes in the Ce3+ surface concentration and oxygen vacancies upon nitrogen doping (N-doping) were determined using x-ray photoelectron spectroscopy and Raman spectroscopy. In-situ fluorescence experiments suggested that the N-doped commercial CeO2 lose its scavenging properties after 41 hours during fuel cell operation at 90oC and 50% RH. However, N-doped high-surface-area CeO2 showed at least 100 hours of continuous scavenging properties under a similar fuel cell operating condition. XPS and Raman measurements suggested that the improved scavenging property of CeO2 upon N-doping was attributed to the increase in Ce3+ surface concentration and oxygen vacancy.
Pd-based Bimetallic Catalysts for Direct Formic Acid Fuel Cells
Authors: Hu Shuozhen , Gao Haijun , Dai Sheng , Scudiero Louis , Ha Su
Published: October 2013

Pd-M (M = Cu and Ni) bimetallic catalysts (films and core-shell nanoparticles) were studied by examining the effect of electronic structural perturbation on the electrochemical activity of the Pd surface toward formic acid oxidation. X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV) are used to obtain the valence band spectra and d-band center shifts and electrochemical activities of the catalysts. XPS analysis indicates a charge transfer from Pd to the transition metals. This electronic perturbation results in an alteration of the interaction between the intermediate species and the Pd surface. As a result, an increase in current density and an improvement in stability of formic acid electrochemical oxidation are observed for the Pd-based bimetallic system compared to pure Pd.
The Effect of Nafion Content on DMFC Electrode Characteristics
Authors: Glüsen Andreas , Müller Martin , Stolten Detlef
Published: October 2013

In this work the influence of the ionomer content in the electrodes on DMFC operation is studied. Nafion content in the anode can be used to control permeation of methanol and water, but has an influence on cell voltage as well. An optimum was found at intermediate Nafion content, where permeation was already reduced without a significant influence on cell voltage. Nafion content in the cathode can be used to improve tolerance towards low air stoichiometry and operation with humidified air. While a Nafion-to-carbon ratio around 0.8 is the optimum for operation with dry air, a significantly lower Nafion-to-carbon ratio of 0.4 should be used for operation with humidified air. On the cathode it was shown that the catalyst layer with the lowest Nafion content had the finest nanopores. For higher Nafion-contents the pore-size maximum was shifted to larger pores and the total nanopore volume was reduced.
The Influence of Liquid Water Interaction between Channel, GDL and CL on Cell Performance
Authors: Kotaka Toshikazu , Tabuchi Yuichiro , Pasaogullari Ugur , Wang Chao-Yang
Published: October 2013

Liquid water in channels is known to have a significant impact on cell performance. This study strives to understand the effect of water interaction between channel, GDL and CL on cell performance by completing coupled cell performance evaluation, liquid water visualization by NRG method and numerical modeling based on M2 model. NRG results showed a peak towards the CL in through-plane distribution of liquid water in the MEA. On the other hand, numerical results suggested very uniform distribution. This discrepancy was explained with a consideration of a porosity distribution of GDL and/or a gap between CL/GDL. This fact indicated that the surface of GDL which has higher porosity and/or the gap led to lower performance as a result of high liquid water saturation in CL. It is therefore important to appropriately engineer the boundary between CL and GDL in order to realize high current density operation.
Fabrication of the Carbon Paper by Wet-Laying of Ozone-Treated Carbon Fibers with Hydrophilic Functional Groups
Authors: Kim Hyunuk , Lee Young-Ju , Lee Dong-Chul , Park Gu-Gon , Yoo Yoonjong
Published: October 2013

Herein we report the fabrication of carbon papers by wet-laying of ozone-treated carbon fibers with hydrophilic functional groups. To improve the dispersion of carbon fibers in water, the surface of carbon fibers was modified by ozone. The surface of ozone-treated carbon fibers contains hydrophilic functional groups such as C-O, C=O and O-C=O, which were characterized by X-ray photoelectron spectroscopy. Such O3-treated CFs were used to fabricate carbon papers by the wet-laid process because of their high dispersion in water. The carbon paper prepared from ozone-treated CFs has higher gas permeability than that from bare CFs. Moreover, the prepared carbon paper from ozone-treated CFs showed better performance in I-V measurement of the single cell than those from bare CFs because of their high gas permeability.
Characterization of MEAs Fabricated by a Carbon Support with the Nano-Channel Structure
Authors: Minamida Yasuto , Zhao Xiaojing , Noda Zhiyun , Hayashi Akari , Sasaki Kazunari
Published: October 2013

With the aim of developing durable electrocatalysts for polymer electrolyte fuel cells, we have been working on Mesoporous Carbon (MC) with the nano-channel structure, whose diameter is ca. 10 nm. By encapsulating Pt catalysts into the pores of MC, improvement of oxygen reduction reaction activity and durability, comparing to Pt deposited on conventional carbon, has been observed in the half-cell evaluation. Improvement on its durability is mainly due to the reduced mobility of Pt particles within pores of MC. In this study, MEAs were newly developed using Pt deposited MC as a cathode catalyst. By controlling the amount of Nafion® and adding a heat treatment step after ball-milling of MC, MEA with IV performance, comparative to Pt deposited on conventional carbon, was successfully developed.
Coupling of Deterministic Contact Mechanics Model and Two-Phase Model to Study the Effect of Catalyst Layer|Microporous Layer Interface on Polymer Electrolyte Fuel Cell Performance
Authors: Zenyuk Iryna V , Taspinar Reyhan , Kalidindi Arvind R , Kumbur Emin Caglan , Litster Shawn
Published: October 2013

We present a two-phase, two-dimensional computational model for studying the effect the microporous layer (MPL) and catalyst layer (CL) interface has on the performance of a polymer electrolyte fuel cell (PEFC). The CL|MPL interface is incorporated as a finite-thickness domain where liquid water saturation levels are determined with van Genuchten water retention curves. These relations are extracted through deterministic contact mechanics model that simulates the three-dimensional interfacial deformation under different levels of compression. Model simulations show high levels of liquid water saturation at the interface that have significant effect on the PEFC performance as opposed to when interfacial contact resistance is included there is a minor performance decrease.
Polyethyleneimine-Based Semi-Interpenetrating Network Membranes for Fuel Cells
Authors: Loureiro Felipe Augusto Moro , Pacheco Pereira Robson , Rocco Ana Maria
Published: October 2013

In the present work, Semi-interpenetrating polymer networks (SIPN) based on polyethyleneimine (PEI) were synthesized and characterized, aiming their future application in fuel cell devices. The membranes were acidified by two methods: (i) absorption of H3PO4 from aqueous solutions and (ii) sulfonation, forming covalently bonded –SO3H. The thermal stability exhibited by the SIPN membranes, above 270 oC, is sufficient for their application in PEMFC and the membranes doped with H3PO4 at 20% show higher conductivity values (of about 0.08 Ω-1cm-1) than those obtained for the best sulfonated sample (10-3 Ω-1cm-1).
Co/N/C Catalysts on a Vertically Aligned Carbon Support for Oxygen Reduction Reaction
Authors: Kawasaki Takashi , Aizawa Masato , Hinogami Reiko , Gyoten Hisaaki
Published: October 2013

The power output of proton exchange membrane fuel cells with non-precious metal cathode catalysts has been insufficient particular for automobile applications. This is largely due to poor mass-transport properties in the thicker catalyst layers compared to those for the Pt-based catalysts. To improve mass-transport properties, we have fabricated a model catalyst comprising cobalt, nitrogen, and carbon (Co/N/C catalyst) on a vertically aligned carbon nanowall(CNW)-like support. The Co/N/C catalyst was formed by electropolymerization of cobalt-coordinated pyrrole on the CNW support which has better structural stability in water than cabon nanotubes. XPS analysis and electrochemical ORR measurements indicate that the electropolymerized catalyst is likely distributed on the side surfaces of each CNW. At a low catalyst loading, the CNW-supported Co/N/C catalyst showed higher ORR current than a planar carbon-supported Co/N/C catalyst. This is presumably due to improved mass transport properties and/or increased surface area. Further investigation is required to separate these effects.
Alkaline Membranes Based on Poly(vinylalcohol) for PEM Fuel Cells
Authors: Benčík Ondrej , Musil Michal , Kunovjánek Miroslav , Šubarda Jiri , Chladil Ladislav , Novák Vitezslav
Published: October 2013

Several samples of polyvinyl alcohol (PVA) based anion exchange membranes were prepared by different ways. Membrane electrode assembly (MEA) structures with platinum electrodes were produced and their loading and power characteristics were measured. The best PVA membrane was also used for MEA structure with MnOx based positive electrode. The measured data were compared with a reference Nafion 115 membrane fuel cell.
Stabilization and Activation of Zirconium Oxide Based Electrocatalysts as PEFC Cathode by Re-Heat Treatment
Authors: Okada Yohei , Ishihara Akimitsu , Matsumoto Masashi , Arao Masazumi , Imai Hideto , Kohno Yuji , Matsuzawa Koichi , Mitsushima Shigenori , Ota Ken-ichiro
Published: October 2013

Development of non-platinum electrocatalyst for oxygen reduction reaction (ORR) is required for real commercialization of polymer electrolyte fuel cells. We focused on group 4 and 5 transition metal oxides, because they have high chemical stability under acidic atmosphere even in high potential region, and are less expensive than platinum. In this study, in order to develop high durability electrocatalysts, zirconium oxide based electrocatalysts prepared by the oxidation of zirconium oxyphthalocyanine in low oxygen pressure were stabilized by heat treatment in the temperature range from 900 to 1200oC for 1 h under nitrogen atmosphere. These catalysts showed higher durability than before stabilization, especially high potential region. Crystallization of surface deposited carbon and zirconium oxide proceeded by heat treatment, and they would improve the durability of the catalyst.
Activity and Durability of Pt/Tin Oxide/Ketjen Black Catalyst as PEFC Cathode
Authors: Kinumoto Taro , Eguchi Naoki , Matsuoka Miki , Tsumura Tomoki , Toyoda Masahiro
Published: October 2013

Pt catalyzed tin dioxide/Ketjen black having various loading amounts of tin oxide nanoparticles, Pt/x-SnO2/KB (x = 0 - 66), were prepared and their ORR (oxygen reduction reaction) activity and durability were studied as the cathode of proton exchange membrane fuel cells (PEMFCs). ORR activity of this catalysts is surely depended on the loading amounts of tin oxide and reaches the maximum at x=58 in this study. Durability of Pt was investigated by repeatedly potential pulse tests between 0.6-1.0 V. It is clarified that the durability considered by ECA is improved by tin dioxide loading. Thus, PEMFC catalyst by using SnO2/KB support is one of the active and durable cathode materials.
The Oxygen Reduction Reaction Catalyzed by Carbon-Supported Copper Phthalocyanine Tetrasulfonic Acid (CuPcTSA/C) by High Temperature Treatment
Authors: Qing Xin , Shi Jingjing , Xu Pan , Xu Jun , Qiao Jinli
Published: October 2013

This work reports the preparation and electrochemical property of carbon-supported copper phthaloctyanine tetrasulfonic acid (CuPcTSA/C) for oxygen reduction reaction (ORR) in alkaline media. The catalyst was synthesized via a combined solvent-impregnation. For optimizing the electrocatalytic activity, the catalyst obtained at room temperature was further treated at high temperature ranged from 600 to 800oC. The catalytic activity was found to be strongly dependent on the heat-treated temperature. Results of electrochemical characterization, which was performed using a rotating disc electrode (RDE) by cyclic voltammetry (CV) and liner sweep voltammetry (LSV), with emphasis on the activity of the catalyst were presented. The resulting CuPcTSA/C-700 of 40/60 mass ratio showed the best catalytic activity in terms of ORR among the overall prepared catalysts, where the onset potential at 0.11V and a half-wave potential at 0.03V were achieved.
Self-Supporting Microporous Layers (MPLs) for PEM Fuel Cells
Authors: Bauder Alexander , Friedrich K. Andreas , Haußmann Jan , Markötter Henning , Manke Ingo , Alink Robert , Scholta Joachim
Published: October 2013

The gas diffusion layer (GDL) plays a crucial role for PEM fuel cell performance. The main requirements of a GDL are the provision of gas and water transport as well as significant electrical and thermal conductivity. For the development of PEMFC diffusion media the still unknown influence of the micro porous layer (MPL) on fuel cell performance is a major obstacle. Therefore a self-supporting MPL was developed because it allows basically the measurement of MPL properties separately from the substrate. To get a correlation of the global intrinsic properties of the MPL, like electrical conductivity or hydrophobicity to fuel cell performance, I-V curves up to limiting current densities and electrochemical impedance spectra (EIS) are measured in a 5 cm² fuel cell setup. Additionally synchrotron X-ray radiography studies were performed to compare the influence of different MPLs on liquid water distribution during fuel cell operation.
Influence of Triple MPL Coated GDL on the PEFC Performance under Low and High Humidity
Authors: Kitahara Tatsumi , Nakajima Hironori , Inamoto Masaoki , Shinto Kosuke
Published: October 2013

Gas diffusion layers (GDLs) coated with a hydrophobic microporous layer (MPL) have been commonly used to improve water management properties of polymer electrolyte fuel cells (PEFCs). In the present study, a novel triple MPL coated GDL, in which the hydrophilic layer was coated on the hydrophobic double MPL, was developed to achieve further enhancement of the PEFC performance under both low and high humidity. Under low humidity, a hydrophilic layer is effective to conserve the humidity of the MEA, while a hydrophobic double MPL prevents the removal of water from the hydrophilic layer. The triple MPL coated GDL, in which the polytetrafluoroethylene (PTFE) content in the hydrophobic MPL in contact with the hydrophilic layer is 30 mass% and that in contact with the carbon paper substrate is 10 mass%, is effective to expel excess water at the catalyst layer, which results in a much higher performance under high humidity.
Experimental Study of the Activity Change Due to Operation History in PEMFC
Authors: Jomori Shinji , Komatsubara Kaori , Nonoyama Nobuaki , Kato Manabu , Yoshida Toshihiko
Published: October 2013

We have developed a new method of precisely determining the activity of cathode catalyst layer in MEA by maintaining the effect of platinum oxides at a constant level and have subsequently studied activity changes resulting from various operational histories. Cyclic voltammetry was used to quantitatively correlate activity changes in the cathode catalyst layer with various operational conditions and demonstrated that activity decreased after low humidity operation and recovered after high humidity operation in a N2 atmosphere at potentials below 0.2 V. The activity changes were found to be very slow and a span of more than 8 hours was required for the activity to reach the steady state. This phenomenon is presumably caused by the adsorption/desorption of ionomer sulfonate groups on the Pt surface, based on observations that the activity changes are consistent with sulfonate group adsorption and dependent on the ionomer structure.
Atomic Imaging and Spectroscopy of Size-Dependent Degradation of Pt Bimetallic Fuel Cell Catalysts
Authors: Gan Lin , Heggen Marc , Cui Chunhua , Rudi Stefan , Strasser Peter
Published: October 2013

Using aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy, we present atomic-scale insights into the size-dependent degradation of Pt-Ni bimetallic oxygen reduction catalysts. We revealed that how particle size can influence the evolution of nanoporosity in the bimetallic nanoparticles and, consequently, their near surface composition, reactivity and stability during long-term electrode potential cycling.
Pt-Free Cathode Catalyst Prepared From Polyimide Fine Particles
Authors: Nabae Yuta , Chokai Masayuki , Ichihara Takeo , Hayakawa Teruaki , Aoki Tsutomu
Published: October 2013

Pt-free cathode catalyst was prepared by pyrolyzing fine nano particles of polyimide. The catalytic activity for oxygen reduction in acidic media was confirmed with the sample paralyzed at over 600 ˚C. The morphology of the fine particles was retained even after the carbonization. Carbon based cathode catalyst with such morphology is quite promising considering the application in polymer electrolyte membrane fuel cells.