bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of Alkaline Fuel Cells Using Hydroxide-Ion Conductive Layered Double Hydroxides
Authors: Tadanaga Kiyoharu , Igarashi Kohei , Kubota Takashi , Miura Akira , Higuchi Mikio
Published: October 2015

Layered double hydroxides (LDHs) intercalated with CO3
2- show high hydroxide ion conductivity of the order of 10-3 S cm-1 under 80% relative humidity. In the present study, (Ni, Mn)-Al LDHs and (Ni, Mn)-Fe LDHs intercalated with CO3
2- were prepared. The conductivity of (Ni, Mn)-Al LDH and (Ni, Mn)-Fe LDH was higher than that of Ni-Al LDH or Ni-Fe LDH. These LDHs were applied to the catalyst layer in an alkaline fuel cell for the improvement of the oxygen reduction reaction (ORR) at the triple phase boundary (TPB) in the catalyst layer. The addition of LDHs to the catalyst layer increased the current for ORR, indicating that hydroxide ion conducting LDHs introduced OH- conducting paths and increased TPB region within the catalyst layer. Above all, the addition of (Ni, Mn)-Fe LDH to the catalyst layer more effectively increased the reduction current for ORR than the addition of (Ni, Mn)-Al LDHs or Ni-Fe LDH. H2-O2 fuel cells with Ni-Al or Mg-Al LDHs as an electrolyte and MnO2 as the cathode catalyst were fabricated. The H2-O2 fuel cells were confirmed to be operated.
Catalyst-Layer Ionomer Imaging of Fuel Cells
Authors: Guetaz Laure , Lopez-Haro Miguel , Escribano Sylvie , Morin Arnaud , Gebel Gerard , Cullen David A. , More Karren L. , Borup Rod L
Published: October 2015

Investigation of membrane/electrode assembly (MEA) microstructure has become an essential step to optimize the MEA components and manufacturing processes or to study the MEA degradation. For these investigations, transmission electron microscopy (TEM) is a tool of choice as it provides direct imaging of the different components. TEM is then widely used for analyzing the catalyst nanoparticles and their carbon support. However, the ionomer inside the electrode is more difficult to be imaged. The difficulties come from the fact that the ionomer forms an ultrathin layer surrounding the carbon particles and in addition, these two components, having similar density, present no difference in contrast. In this work, we show how the recent progresses in TEM techniques as spherical aberration (Cs) corrected HRTEM, electron tomography and X-EDS elemental mapping provide new possibilities for imaging this ionomer network and consequently to study its degradation.
Investigation of Solvent and Carbon Particles Behavior during Drying Process from Catalyst Ink to Catalyst Layer
Authors: Suzuki Takahiro , Kobayashi Masamichi , Tanaka Hiroki , Hayase Masanori , Tsushima Shohji
Published: October 2015

The electrical resistance and evaporation rate of a slurry composed of a solvent, carbon and ionomer were measured. Electrical resistance was measured with a four-point probe, and the evaporation rate was monitored with an electric balance. The drying is a key process for porous electrode fabrication such as catalyst layers used in proton exchange membrane fuel cells. Carbon particles behavior affects a formed porous structure, and it can affect cell performance. Solvent evaporation is also important to understand dynamics in the drying process of the slurry. Electrical resistance and weight variation represent carbon agglomeration and solvent evaporation, respectively. Three types of the slurry which differ in carbon content were measured. The higher carbon content slurry took a shorter time for agglomeration and drying. The difference of the agglomeration time and the drying time is larger in the low carbon content slurry. This result indicates that the agglomeration proceed not only by solvent evaporation.
Operando Sub-Second Tomographic Imaging of Water in PEFC Gas Diffusion Layers
Authors: Eller Jens , Marone Federica , Büchi Felix N
Published: October 2015

The evolution of the liquid water distribution in the gas diffusion layers (GDL) of polymer electrolyte fuel cells (PEFC) during transient operation conditions was visualized by operando sub-second X-ray tomographic microscopy (XTM) at the TOMCAT beamline of the Swiss Light Source. The consequences of the reduced exposure time and lower number of angular steps on image quality are discussed and the temporal and spatial development of the water distribution in the channel and the GDL following a current density variation from 0.1 A/cm² to 1.0 A/cm² are presented. Special focus is put on channel vs. land variations, formation of liquid water percolation paths, their stability over time as well as the influence of the water saturation on diffusive gas transport.
Effects of Reactant Gases on HT-PEM Fuel Cells
Authors: Rastedt Maren , Pinar Francisco Javier , Pilinski Nadine , Wagner Peter
Published: October 2015

One important task of the European project CISTEM is the investigation of degradation processes, which may be caused by different operating conditions. The possibility to use different fuels and oxidants makes a HT-PEM fuel cell much more flexible and versatile for application. Therefore, some degradation effects induced by varied reactant gases will be described in this work. Intensive investigation of MEAs under equal test conditions (H2/O2, constant load at 0.3 A/cm²) provided contradictory degradation results with degradation rates of -8.0 µV/h and -70 µV/h for the same MEA type. The same trend has been observed with other fuel supply options. Fuel cells operated with hydrogen/air or with synthetic reformate/air show similar low and high degradation rates. This paper discusses a possible explanation for such differences. Post-mortem analysis on MEAs with high degradation rates are performed to provide a better understanding of causes leading to such high degradation rates.
Instability Of Commercial Pt/C And Pd/C Electrocatalysts In Alkaline Media
Authors: Zadick Anicet , Dubau Laetitia , Chatenet Marian , Demirci Umit , Serov Alexey , Atanassov Plamen
Published: October 2015

The electrochemical degradation of commercial (E-TEK) Pt and Pd nanoparticles supported on Vulcan XC-72 (noted Pt/C and Pd/C) was performed in NaOH electrolyte solutions. The fate of the electrocatalysts upon accelerated stress test (AST) in alkaline medium was compared to that in acidic (H2SO4 and HClO4) electrolyte solutions. Electrochemical measurements, combined with Identical-Location Transmission Electron Microscopy (ILTEM) demonstrated that the Pt/C catalyst degradation in 0.1 M NaOH at 25°C is extremely severe for a mild accelerated stress test (AST – 150 cycles, at 100 mV sec-1 and 25°C, between 0.1 and 1.23 V vs. RHE), mainly owing to large nanoparticles detachment from the carbon substrate. For Pd/C, an opposite trend is found: the degradations are harsher in acidic environment.
Imaging Phosphoric Acid Migration in High Temperature Polymer Electrolyte Fuel Cells by X-Ray Tomographic Microscopy
Authors: Eberhardt Sebastian H. , Marone Federica , Stampanoni Marco , Büchi Felix N , Schmidt Thomas J.
Published: October 2015

High temperature polymer electrolyte fuel cells (HT-PEFC) exhibit extensive phosphoric acid electrolyte migration from cathode to anode under high current operation. In this work synchrotron based operando X-ray tomographic microscopy (XTM) was used to study the influence of current density, membrane material (DMAc film casted PBI and PPA-process membranes) and phosphoric acid loading on the extent of electrolyte migration.
Pt-decorated TiO2 Electrocatalysts for PEFCs
Authors: Iwami Masahiro , Horiguchi Dai , Noda Zhiyun , Hayashi Akari , Sasaki Kazunari
Published: October 2015

For polymer electrolyte fuel cell (PEFC) electrocatalysts, carbon corrosion is one of the important technological issues to be solved. TiO2 is a possible alternative support material. In this study, vapor-grown carbon fiber (VGCF-H) conductive fillers are applied as the built-in electron-conductive backbone, on which Nb-doped TiO2 is coated and Pt nanoparticles are then impregnated. FESEM images of Pt/Ti0.95Nb0.05O2/VGCF-H reveal selective impregnation of Pt nanoparticles on the TiO2 grains rather than the VGCF-H conductive fillers. This conductive-filler-integrated electrocatalyst exhibits relatively higher electrochemical surface area (ECSA) and oxygen reduction reaction (ORR) activity, compared to the electrocatalysts without conductive fillers.
Effect of Alloy Composition on Electrocatalytic Activity of PdAu Core/Pt Shell Nanoparticle Catalysts for Oxygen Reduction Reaction
Authors: Kuwahara Taiki , Chiku Masanobu , Higuchi Eiji , Inoue Hiroshi
Published: October 2015

PdAu alloy nanoparticles with different Au contents were prepared on carbon black (Pd100-xAux/CB) by bubbling CO as a reducing agent in acetonitrile solution containing Pd(CH3COO)2 and KAuCl4. Then the alloy composition of PdAu nanoparticles was controlled by changing the mixing molar ratio of precursors. XRD exhibited that the neighbor interatomic distance was increased with the Au content for Pd100-xAux/CB. The electrocatalytic activity for oxygen reduction reaction (ORR) of the Pt shell monolayer-modified Pd100-xAux core nanoparticles (Pt/Pd100-xAux/CB) was related to the Au content in the core with a volcano curve, which indicated that the ORR activity can be controlled by the core composition. Furthermore, the ORR activity per unit mass at 0.9 V vs. RHE for Pt/Pd90Au10/CB was ca. 8 times as high as that of commercial Pt/CB.
Facile Synthesis of Three-Dimensional Graphene Nanomaterials via Supercritical Fluid for Oxygen Reduction Reaction
Authors: Zhu Chengzhou , Zhou Yazhou , Fu Shaofang , Du Dan , Lin Yuehe
Published: October 2015

The considerable interest in polymer electrolyte membrane fuel cells (PEMFCs) has sparked a sustained research effort on more active and reliable oxygen reduction reaction (ORR) electrocatalyst. 3D porous architectures featured by higher specific surface areas and larger pore volumes have received great interest, which not only maximize the availability of electron transfer within nanosized electrocatalyst surface area but also provide better mass transport of reactants to the electrocatalyst. Supercritical CO2 (scCO2) process offers an elegant and efficient route for the synthesis and processing of novel nanocomposite materials. Herein, we developed the scCO2 technique to synthesize boron-doped 3D graphene and low Pt group metal-based graphene/PtFe with 3D porous nanostructures. Significantly, these 3D nanocomposites show excellent electrocatalytic activity and high stability for the ORR, holding great promise for the development of PEMFCs.
Development of Free-Metal Electrocatalyst from Inexpensive Sources of Carbon: A Novel Electrode Material for Cathode Reaction in PEM Fuel Cells
Authors: Alonso-Lemus Ivonne Liliana , Lardizabal Daniel , de la Torre Saenz Luis , Sanchez-Castro Maria Esther , Rodríguez-Varela F.J.
Published: October 2015

Recently, free noble metal electrocatalysts have been obtained, which are capable of carrying out the oxygen reduction reaction (ORR) with comparable performance to Pt. These novel electrocatalysts are doped nanostructured carbon (ej. nitrogen doped carbon nanotubes N-NTC and nitrogen doped reduced graphene, N-rG). Nowadays, the synthesis of these nanostructured materials has several technological challenges, because it production is still expensive and has a significant environmental impact. In this work, we have obtained novel metal-free electrocatalysts from two different inexpensive carbon source: i) an organic waste and ii) mineral coal from Sabinas region in Coahuila Mexico. These electrocatalysts have a significantly lower cost than conventional platinum-based electrocatalysts or than nanostructured carbon free-metal catalyst. The results show that these electrocatalysts are an inexpensive, environmental friendly and promising alternative for use as cathodes in PEMFC.
Investigation of PtCo/Graphene and PtCoRu/Graphene Catalysts for Oxygen Reduction Reaction
Authors: Kepeniene Virginija , Stagniunaite Raminta , Tamasauskaite-Tamasiunaite Loreta , Norkus Eugenijus
Published: October 2015

In the present study a rapid microwave heating method was used to prepare the graphene supported PtCo and PtCoRu catalysts. The catalytic activity of the PtCo/graphene and PtCoRu/graphene catalysts for oxygen reduction reaction was investigated. Physical characterization of the catalysts was performed by Transmission Electron Microscopy and Inductively Coupled Plasma Optical Emission Spectroscopy techniques. It was found that the PtCo/graphene and PtCoRu/graphene catalysts show enhanced activity towards oxygen reduction as compared with that of bare Pt/graphene catalyst. The PtCo/graphene and PtCoRu/graphene catalysts show higher onset potentials, as well as higher current densities towards oxygen reduction reaction as compared with those at the bare Pt/graphene catalyst.
Investigation of Stability Reduction in PtCoMn Ternary Alloy Catalyst for PEFCs
Authors: Ishida Minoru , Matsutani Koichi
Published: October 2015

In this study, PtCoMn / High surface area carbon (HSAC) ternary alloy catalysts were evaluated stability against voltage cycling test in MEA. Oxygen reduction reaction (ORR) activity of PtCoMn catalyst decreased gradually in each test. The stability of PtCoMn / HSAC was not comparable to existing Pt and PtCo catalysts. To understand the mechanism of decreasing ORR activity of PtCoMn / HSAC, the MEA which was used in voltage cycling test was investigated by SEM / EDX mapping analysis and EPMA line analysis. As a result of the analysis, a lot of Pt particles were found at the interface of Nafion membrane and cathode catalyst, and Co and Mn elements were detected in the membrane. These results suggest that not only Pt but also Co and Mn in the PtCoMn catalyst dissolved and turn to be metal ions during the test. Then, Pt ions were re-deposited as Pt metal particles at the interface during the test. These results indicate that stability decrease of PtCoMn catalyst would be caused by the dissolution of the metal in the catalyst.
Improvement for the Mass Transfer in the Anode Electrode of Direct Formic Acid Fuel Cell Fabricated by Ultrasonic Spray
Authors: Matsuoka Fumihikko , Tsujiguchi Takuya , Osaka Yugo , Kodama Akio
Published: October 2015

The power generation characteristics of the DFAFC in which anode were fabricated different method, ultrasonic spray method and deposit method were compared by measuring the overpotentials of the anode and the cathode, individually. The highest performance was obtained when anode catalyst layer was fabricated by ultrasonic spray method since the overpotential of the anode electrode fabricated by ultrasonic spray method was lower than that fabricated by deposit method. From the overpotential measurements, it was found that the anode overpotential could be reduced when the anode electrode was fabricated by ultrasonic spray due to the thin anode catalyst layer. From these results, it is considered that the ultrasonic spray is suitable as the fabrication of anode catalyst layer of the DFAFC.
Molecular Simulation of Oxygen Solubility and Diffusivity in Ionomer on Pt Surface
Authors: Kurihara Yuya , Mabuchi Takuya , Tokumasu Takashi
Published: October 2015

We analyzed the oxygen permeability through the ionomer on the Pt surface using molecular dynamics simulations. We calculated the density distributions of ionomer components and oxygen, the number of permeated oxygen through the ionomer, and the oxygen solubility. As a result, we have found that the oxygen permeability decreases as water content increases. In the ionomer/gas interface and the bulk region, the oxygen solubility decreases. Beside, compared with the structure properties of bulk membranes, the oxygen diffusivity is considered to increase as water content increases due to the swelling of the regions. In the ionomer/Pt interface, the oxygen solubility decreases with increasing water content, besides it is considered that the oxygen diffusivity decreases with increasing water content, because the solvent fills the pores which are pathways of oxygen.
Molecular Dynamics Study of Proton Transport in Modeled Water Cluster Structure of Polymer Electrolyte Membrane
Authors: Mabuchi Takuya , Tokumasu Takashi
Published: October 2015

Molecular dynamics simulations have been performed to study the effects of water cluster structure on proton transport (PT) properties. The systems were built to closely approximate the proposed hydrophilic cluster structures (e.g. the cylinder model and the lamellar model) that are the most typical morphological models of Nafion. The PT properties were estimated in terms of diffusion coefficient and proton pathway using a modified two-state empirical valence bond (EVB) model. The diffusion coefficients in each dimension were calculated and correlated with the cluster size as well as the type of cluster models. It was found that proton diffusion is strongly affected by the cluster model and its size, which can be associated with the proton pathway in each cluster model. The influence of the sulfonate groups on the PT properties were also investigated. Our simulation results provide insight into quantitative information about PT properties in atomic level.
Multiscale Model of Proton Transport in Perfluorosulfonic-Acid Membrane
Authors: Crothers Andrew Robert , Radke Clayton J. , Weber Adam Z
Published: October 2015

Ionic conductivity in phase-separated polymer-electrolyte–fuel-cell membranes is limited by the multiple scales via which protons travel. The interactions of protons in the conducting pores determine the mobility at the nanoscale, while the tortuosity of the conductive phase dictates the macroscopic conductivity. Previous efforts to model transport in this multiscale network have relied on assumptions of the morphology. In this paper, direct imaging of a hydrated membrane is used to construct a network through which transport occurs. Our results indicate that pore-level conductivity is lower than bulk solution conductivity due to interactions between protons and negatively charged moieties of the polymer. The distribution of sizes of the hydrophilic domains leads to inhomogeneous transport pathways across the network.
Application of Modified-ACLS Electrodes on Low-platinum PEFCs
Authors: Mei Wu , Fukazawa Taishi , Yang Tianyi , Yoshinaga Norihiro , Kanai Yuta
Published: October 2015

Alternating catalyst layer structure (ACLS) is a promising low-platinum technology for the PEFC application. This report discusses modification of ACLS in recent years, focusing on the enhancement of oxygen reduction reaction activity (ORR) and load cycle durability. For modified-ACLS electrodes (M-electrodes), single cell measurement showed about 6 times ORR specific activity compared with commercial Pt3Co/C. Excellent durability of M-electrodes was confirmed even with a Pt loading of 0.025 mgPt/cm2, revealing the possibility of their application as ultra-low-platinum PEFC anodes.
Analysis of Kinetic Parameters and Effect of Pt Loading on Cell Performance of PEFC Electrodes Prepared by Inkjet Printing
Authors: Shukla Shantanu , Domican Kailyn , Secanell Marc
Published: October 2015

The changes to cell performance, Tafel slope and reaction order with varying Pt loadings and catalyst layer (CL) thickness of 0.014 to 0.1mg/cm2 and 1 μm to 5.5 μm respectively are studied by using a varietyof oxygen partial pressures for the case of thin, low-loaded inkjet printed electrodes. For 20% Pt/C catalyst, a steep increase in performance was observed as the Pt loading increased to 0.079 mg/cm2, corresponding to a CL thickness of around 4.4 μm. At higher Pt loadings, the improvement in the cell performance was substantially reduced. Higher cell performance for the inkjet printed CCMs could be obtained by altering the operating conditions (e.g., operating at a higher back-pressure) rather than increasing the Pt loading. Active area of the electrodes decreased from 57 to 41 m2/g as the Pt loading increased from 0.026 to 0.1 mg/cm2. Below the transition voltage of 0.8 ViRFree, Tafel slope was found to be a function ofthe Pt loading and oxygen partial pressure (PO2). The kinetic reaction order (γ) increased with increasing overpotential for all the Pt loading cases.
Enhanced Ethanol Oxidation Activity for a Direct Fuel Cell with Silica-Carbon Composite Catalyst Support
Authors: Ishitobi Hirokazu , Ino Yurina , Nakagawa Nobuyoshi
Published: October 2015

The technical issue of direct ethanol fuel cells is slow kinetics and low CO2 selectivity of ethanol electrooxidation by using Pt. Silica embedded carbon nanofiber (SECNF) was prepared as a catalyst support to improve electrocatalytic characteristics. Catalysts were characterized by SEM and XRD. Electrochemical measurements were performed to analyze catalytic activity and electrochemical active surface area of Pt/SECNF. The mass activity of Pt/SECNF was twice as high that of Pt/carbon nanofiber. In contrast, the value of ECSA was almost constant for each nanofiber catalyst. However, too much SiO2 addition was not preferable in the viewpoint of specific resistance of the sample layer. The activity enhancement is attributed to the improvement of specific activity for Pt/SECNF by the interaction between Pt and SiO2.
Influence of Structural Effects on Platinum Electrodes in the Preferential Adsorption of CO and Methanol in Acid Media
Authors: Paulino Marcia Elizangela , Colmati Flavio , Gonzalez Ernesto Rafael
Published: October 2015

Methanol has been the subject of many studies in the last decade within the possible fuels for the fuel cell technology. As known the methanol electro-oxidation pathway on platinum follows by formation of formic acid, carbon monoxide and finally carbon dioxide and water. In this work it is shown the influence of structural effect on platinum electrodes for the electro-oxidation of CO and methanol. Moreover, it is shown the effect of the CO adsorption on platinum on methanol electro-oxidation. Methanol electro-oxidation follows a different sequence of the potential dependence depending on surface orientation. The highest potential for CO electro-oxidation was observed on Pt(111) followed by Pt(100), and Pt(110). There are two groups of platinum surfaces for methanol electro-oxidation: self-cleaning, and self-poisoning. Self-cleaning reduce the potential of the COads electro-oxidation whereas self-poisoning increase the potential of the COads electro-oxidation.
Activity and Durability of Iridium Nanoparticles in the Oxygen Evolution Reaction
Authors: Alia Shaun M , Pylypenko Svitlana , Neyerlin K.C. , Kocha Shyam S , Pivovar Bryan S
Published: October 2015

Unsupported iridium (Ir) nanoparticles, a benchmark catalyst in acidic electrolyzers, are investigated for oxygen evolution activity in rotating disk electrode (RDE) half-cells. Mercury underpotential deposition, used to evaluate the electrochemical surface areas (ECAs) of Ir, produces similar values prior to and following oxygen evolution testing and irreversible surface oxidation; stable ECA measurements allow for the study of site-specific activities prior to and following accelerated stress tests. Durability testing results in increasing activity losses due to particle growth at moderate potential and Ir dissolution at higher potential. Although the prolonged formation of oxygen bubbles may destabilize the catalyst layer, accelerated stress tests in hydrogen peroxide and formic acid confirm that the losses are primarily potential dependent. This study establishes RDE testing protocols for Ir in oxygen evolution. The observed durability losses have significant implications on acidic electrolyzers, particularly at low Ir loadings.
NSTF Advances for PEM Electrolysis - the Effect of Alloying on Activity of NSTF Electrolyzer Catalysts and Performance of NSTF Based PEM Electrolyzers
Authors: Lewinski Krzysztof A. , van der Vliet Dennis , Luopa Sean M.
Published: October 2015

Current interest in developing environmentally sound methods of energy generation and storage has led to a renewed interest in hydrogen generation via polymer electrolyte membrane (PEM) electrolysis. PEM electrolysis could provide a clean alternative to existing hydrogen production methods, such as steam reforming, if both the capitalization and operational expenses can be properly managed to improve its economic benefits as well as its environmental benefit.In this paper we explore one method of reducing the capital expenses by both lowering the amount of PGMs used to operate a PEM electrolyzer, and increasing the operating power level per cell. We start off by using 3M’s nano-structured thin film (NSTF) support to reduce the total mass required compared to conventional dispersed catalysts on both the anode and cathode, with exceptional success. Not only is such a NSTF electrolyzer able to operate with only 0.25 mgIr·cm-2 on the anode, in addition to 0.25 mgPt·cm-2 on the cathode, the maximum current density we can obtain with this setup approaches 20 A·cm-2. In an attempt to improve the electrode conductivity and lower Ohmic losses over standard iridium oxide, we continued by testing iridium-platinum alloys in both conventional single cell electrolyzer tests and rotating disk electrode tests. Unfortunately, it appears Pt drastically inhibits the OER on the resulting IrxPty-NSTF alloy catalyst.
Influence of the Interfacial Water Transfer on the Analysis of Dynamic Sorption and Desorption Experiments in Nafion® Membrane
Authors: Didierjean Sophie , Perrin Jean-Christophe , Xu Feina , Maranzana Gael , Mainka Julia , Lottin Olivier
Published: October 2015

Water sorption and desorption in Nafion®117 membranes in acid form were studied by means of dynamic experiments as a response of relative humidity steps. The recorded mass variations with time of the membrane samples were analyzed by means of the least squares method based on a model that takes into account an interfacial mass transfer coefficient between the membrane and the bulk humid gas, diffusion being assumed negligible. In the case of large steps in relative humidity, the model predicts that the kinetics of desorption is much faster than the kinetics of sorption. The comparisons with the experimental results for large and small steps in relative humidity show a good accordance and give the value of the corresponding mass transfer coefficient.
Dual Nafion/Polyaniline Nanofibers Architecture for Applications in Fuel Cells Electrodes
Authors: Simotwo Silas , Kalra Vibha
Published: October 2015

Nanostructured non-woven fiber mats of Nafion, polyaniline (PANI) and dual Nafion/polyaniline nanofibers were fabricated via electrospinning technique. Nafion/PANI nanofibers composite was prepared by simultaneous electrospinning of Nafion and PANI solutions onto a single collector. Poly (ethylene oxide) (PEO) was added to enhance chain entanglements and therefore, the electrospinnability of both polymer solutions. Electrochemical impedance spectroscopy was used to characterize the conductivity of the nanofiber mats. The proton and electron conductivities of the Nafion/PANI composite mats were decoupled using equivalent circuit. Dual nanofibers mat with Nafion/PANI weight composition of 61/39 showed a proton conductivity of 0.032 S/cm and electron conductivity of 0.041 S/cm. Such dual nanofiber mats with percolating phases of electron and proton conductors and three-dimensional through–connected inter-fiber pore structure can potentially serve as excellent catalyst supports for PEMFCs.
Autostack - CORE - Industry Led European Consortium to Develop Next Generation Automotive Stack Hardware
Authors: Martin André , Jörissen Ludwig
Published: October 2015

High power density stack technology is a key enabler for use of fuel cells in automotive applications. AutoStack-CORE is a colaborative project establishing a coalition from component manufacturers, OEMs and research orgainzations to develop automotive stack technology with superior power density and performance while using components manufactured at an industrial scale meeting commercial target cost.The stack design is based on a joint specification including a packaging constraint analysis developed in a previous project. Within the project 2 evolutions of stack hardware will be built. A final evolution will be realized as a design only.In this paper the key achievements of the evolution 1 design will be shown. The stack is based on metallic bipolar plates to achieve high power density (2.7 kW/l) and specific power (2.0 kW/kg). A cost engineeering study according to automotive standards revealed specific cost of 47.83 €/kW when using the same parameters and aggregated to the same level as the 2013 update of the cost study by Strategic Analysis.The stack has been thoroughly tested on short stack and full stack level. Robust operation within the limits of the specification as well as freeze-start capability down to -20 °C could be demonstrated. The consortium completed a design review identifying the necessary steps for the veolution 2 design phase.
A CFD Simulation for an Air Breathing PEMFC for Power Source Portable Applications
Authors: Carcadea Elena , Varlam Mihai , Stefanescu Ioan , Ingham Derek , Marinoiu Adriana , Patularu Laurentiu , Raceanu Mircea , Schitea Dorin
Published: October 2015

This paper presents a numerical investigation for a 44 cm2 air breathing PEM fuel cell. We analyzed the influence of some operating and design parameters on the cell performance. The numerical solution based on ANSYS Multiphysics software and Fuel Cell Module offered an optimal performance at a cell with the cathode channel dimensions of 1.5 mm x 1.5 mm. Analyzing the polarization curves it can be noticed that for operating voltages greater than 0.75V, the channel width and depth has only a small influence on the performance, while at lower operating voltages the influence of the channels size on the performance become significant. In identifying the critical parameters and for having an insight into physical mechanisms that can influence the fuel cell we analyzed the water mass fraction and membrane protonic conductivity distributions, the relative humidity and temperature in the anode and the pressure and temperature in the cathode side.
Carbon Corrosion in PEM Fuel Cells during Drive Cycle Operation
Authors: Borup Rod L , Papadias Dionissios D. , Mukundan Rangachary , Spernjak Dusan , Langlois David A. , Ahluwalia Rajesh , More Karren L. , Grot Stephen
Published: October 2015

One of the major contributors to degradation involves the electrocatalyst, including the corrosion of the carbons used as catalyst supports, which leads to changes in the catalyst layer structure. We have measured and quantified carbon corrosion during drive cycle operation and as a variation of the upper and lower potential limits used during drive cycle operation. The amount of carbon corrosion is exacerbated by the voltage cycling inherent in the drive cycle compared with constant potential operation. The potential gap between upper and lower potentials appears to be more important than the absolute operating potentials in the normal operating potential regime (0.40V to 0.95V) as changes in the measured carbon corrosion are similar when the upper potential was lower compared to raising the lower potential. Catalyst layer thinning was observed during the simulated drive cycle operation which had an associated decrease in catalyst layer porosity. This catalyst layer thinning is not due solely to carbon corrosion, although carbon corrosion likely plays a role; much of this thinning must be from compaction of the material in the catalyst layer. The decrease in catalyst layer porosity leads to additional performance losses due to mass transport losses.
Current Density Distribution in the Lateral Direction of Conventional and Interdigitated Flow Field
Authors: Shrivastava Udit N , Tajiri Kazuya
Published: October 2015

The design of flow field significantly affects the mass transport in an operating PEMFC. One example of such design is interdigitated flow field. In this kind of flow field depending on the location both convective and diffusive mass transfer occur in the land-channel direction. These two modes of mass transfer influence the local current and water generation in the land-channel direction. To understand the difference between these two mass transport mechanism the comparison of local current density and ohmic resistance distribution in the land-channel direction of conventional and interdigitated flow fields is imperative. This work is focused on measurement of current density and ohmic resistance distribution in the land-channel direction of a conventional and an interdigitated flow fields. A customized catalyst coated membrane of active area 9 mm2 was prepared and a segmented anode was employed to measure the parameters mentioned at 350 µm resolution in the land-channel direction of an interdigitated flow field. At 60 oC and 90 % RH current density and ohmic resistance distribution were measured for both kind of flow fields, and discussion is presented.
Investigation of Mass Transport Losses in Polymer Electrolyte Electrolysis Cells
Authors: Suermann Michel , Schmidt Thomas J. , Büchi Felix N
Published: October 2015

In polymer electrolyte electrolysis cells different processes contribute to the losses with increasing current. While the contribution of the ohmic overpotential is well characterized and can easily be determined by measuring the high frequency resistance of the cell, the kinetic and mass transport losses are more difficult to characterize and understand. For determining the mass transport losses, also the kinetic losses need to be characterized, which needs careful analysis in particular when pressure varies over a wide range. The dependence of the mass transport losses is determined as function of the structures employed as current collectors, i.e., possible two-phase phenomena in the porous structures as well as for different operating conditions with respect to pressure and temperature. The results show that over a wide range of current densities a quite significant part of the voltage losses can to be attributed to mass transport.
Ta-Based Catalyst Support for Proton Exchange Membrane Fuel Cell Applications
Authors: Abhayawardhana Anusha D. , Birss Viola
Published: October 2015

An ordered mesporous Colloid Imprinted Carbon with 80 nm sized pores (CIC80), a nitrided CIC80 (N-CIC80), and Ta oxynitride nanoparticles on nitrided CIC80 (TaOxNy NPs/N-CIC80) were synthesized and evaluated as possible supports for Pt electrocatalysts in PEMFC applications. Transmission electron microscopy images showed that they have the expected pore size and that the TaOxNy NPs are in the range of 5-20 nm in diameter. Potential stepping experiments revealed that the TaOxNy NPs/N-CIC80 composite exhibits the highest corrosion resistance in 0.5 M H2SO4, followed by N-CIC80 and then CIC80. Consistent with this, cyclic voltammetry revealed that the TaOxNy NPs/N-CIC80 composite gave the smallest increase in surface area after the potential stepping experiment, followed by N-CIC80 and CIC80. These results suggest that a nitrided carbon surface is more corrosion resistant than carbon alone, and that the TaOxNy NPs, which are themselves extremely stable, are conferring some of their stability to the carbon substrate.
Understanding Liquid-Water Management in PEFCs Using X-Ray Computed Tomography and Modeling
Authors: Zenyuk Iryna V , Weber Adam Z
Published: October 2015

Optimal liquid-water management is essential for commercializing polymer-electrolyte fuel cells, especially those with next-generation material sets. At low operating temperatures there is a need to remove liquid water from the cathode electrode where it can impede reactant transport. Optimization of water transport and removal requires a careful design consideration for the porous carbon components, specifically the gas-diffusion layers (GDLs). Two-phase transport inside the GDLs, especially during operation, is complex and requires detailed knowledge of a given GDLs’ morphology and transport properties. In this paper, the GDL’s morphological properties are elucidated using synchrotron-based X-ray micro computed tomography (XCT) and in-situ water-distributions for two sets of GDLs. The XCT studies are complemented with two-dimensional modeling studies to gain an understanding of liquid-water transport under in-operando conditions.
Impact of Water Management on Local Potential Evolutions during PEM Fuel Cell Operation with Dead-Ended Anode
Authors: Abbou Sofyane , Dillet Jérôme , Maranzana Gael , Didierjean Sophie , Lottin Olivier
Published: October 2015

Operating a PEMFC with a dead-ended anode may lead to local fuel-starvation because of water and possibly nitrogen accumulation in the anode compartment. In previous works, we used a segmented linear cell with reference electrodes to monitor simultaneously the local potentials and current densities during dead-ended anode operation. The results indicated that water transport as well as nitrogen crossover through the membrane were most probably the two key factors governing fuel starvation. In this work, we evaluated with more details the contributions of nitrogen crossover and water transport to hydrogen starvation by using different cooling temperature on the cathode and anode sides. The results show that with a colder anode side, fuel-starvation was faster. In the opposite case of a hotter anode plate, water accumulation in the anode compartment was limited, suggesting that nitrogen crossover through the membrane was probably the main reason for hydrogen starvation in this case while water it is water in regular operation (i.e., with identical cooling temperature on both sides).
Influence of the Gas Diffusion Layer Compression on the Oxygen Mass Transport in PEM Fuel Cells
Authors: Simon Christoph , Hasché Frédéric , Müller David , Gasteiger Hubert A.
Published: October 2015

The compression of the gas diffusion layer is an important parameter in a fuel cell setup. Its influence on the oxygen mass transport is investigated by the measurement of the limiting current density with diluted oxygen. For low compressions of <15% based on its initial thickness, we found that the oxygen mass transport resistance is increasing significantly in the high current region where condensation takes place due to increased product water formation. We hypothesize that a liquid water film is blocking the oxygen transport pathway at the interface between microporous layer and electrode. Furthermore, we discovered an earlier onset of water condensation at high compressions caused by a reduction of the thermal contact resistance.
MicroRNA-145 repairs infarcted myocardium by accelerating cardiomyocyte autophagy
Authors: Higashi Kenshi , Yamada Yoshihisa , Minatoguchi Shingo , Baba Shinya , Iwasa Masamitsu , Kanamori Hiromitsu , Kawasaki Masanori , Nishigaki Kazuhiko , Takemura Genzou , Kumazaki Minami , Akao Yukihiro , Minatoguchi Shinya
Published: October 2015

We investigated whether microRNA-145 (miR-145) has a cardioprotective effect in a rabbit model of myocardial infarction (MI) and in H9c2 rat cardiomyoblasts. Rabbits underwent 30 min of coronary occlusion, followed by 2 days or 2 wk of reperfusion. Control microRNA (control group; 2.5 nmol/kg, n = 10) or miR-145 (miR-145 group, 2.5 nmol/kg, n = 10) encapsulated in liposomes was intravenously administered immediately after the start of reperfusion. H9c2 rat cardiomyoblasts were transfected with miR-145. The MI size was significantly smaller in the miR-145 group than in the control group at 2 days and 2 wk post-MI. miR-145 had improved the cardiac function and remodeling at 2 wk post-MI. These effects were reversed by chloroquine. Western blot analysis showed that miR-145 accelerated the transition of LC3B I to II and downregulated p62/SQSTM1 at 2 days or 2 wk after MI, but not at 4 wk, and activated Akt in the ischemic area at 2 days after MI. miR-145 inhibited the growth of H9c2 cells, accelerated the transition of LC3B I to II, and increased phosphorylated Akt in the H9c2 cells at 2 days after miR-145 transfection. Antagomir-145 significantly abolished the morphological change, the transition of LC3B I to II, and the increased phosphorylated Akt induced by miR-145 in H9c2 cells. We determined fibroblast growth factor receptor substrate 2 mRNA to be a target of miR-145, both in an in vivo model and in H9c2 cells. In conclusion, post-MI treatment with miR-145 protected the heart through the induction of cardiomyocyte autophagy by targeting fibroblast growth factor receptor substrate 2.
IFN-β affects the angiogenic potential of circulating angiogenic cells by activating calpain 1
Authors: Yıldırım Cansu , Favre Julie , Weijers Ester M. , Fontijn Ruud D. , van Wijhe Michiel H. , van Vliet Sandra J. , Boon Reinier A. , Koolwijk Pieter , van der Pouw Kraan Tineke C. T. M. , Horrevoets Anton J. G.
Published: October 2015

Circulating angiogenic cells (CACs) are monocyte-derived cells with endothelial characteristics, which contribute to both angiogenesis and arteriogenesis in a paracrine way. Interferon-β (IFN-β) is known to inhibit these divergent processes in animals and patients. We hypothesized that IFN-β might act by affecting the differentiation and function of CACs. CACs were cultured from peripheral blood mononuclear cells and phenotypically characterized by surface expression of monocytic and endothelial markers. IFN-β significantly reduced the number of CACs by 18–64%. Apoptosis was not induced by IFN-β, neither in mononuclear cells during differentiation, nor after maturation to CACs. Rather, IFN-β impaired adhesion to, and spreading on, fibronectin, which was dependent on α5β1(VLA-5)-integrin. IFN-β affected the function of VLA-5 in mature CACs, leading to rounding and detachment of cells, by induction of calpain 1 activity. Cell rounding and detachment was completely reversed by inhibition of calpain 1 activity in mature CACs. During in vitro capillary formation, CAC addition and calpain 1 inhibition enhanced sprouting of endothelial cells to a comparable extent, but were not sufficient to rescue tube formation in the presence of IFN-β. We show that the IFN-β-induced reduction of the numbers of in vitro differentiated CACs is based on activation of calpain 1, resulting in an attenuated adhesion to extracellular matrix proteins via VLA-5. In vivo, this could lead to inhibition of vessel formation due to reduction of the locally recruited CAC numbers and their paracrine angiogenic factors.
Homeostasis and its disruption in the lung microbiome
Authors: Dickson Robert P. , Erb-Downward John R. , Huffnagle Gary B.
Published: October 2015

The disciplines of physiology and ecology are united by the shared centrality of the concept of homeostasis: the stability of a complex system via internal mechanisms of self-regulation, resilient to external perturbation. In the past decade, these fields of study have been bridged by the discovery of the lung microbiome. The respiratory tract, long considered sterile, is in fact a dynamic ecosystem of microbiota, intimately associated with the host inflammatory response, altered in disease states. If the microbiome is a “newly discovered organ,” ecology is the language we use to explain how it establishes, maintains, and loses homeostasis. In this essay, we review recent insights into the feedback mechanisms by which the lung microbiome and the host response are regulated in health and dysregulated in acute and chronic lung disease. We propose three explanatory models supported by recent studies: the adapted island model of lung biogeography, nutritional homeostasis at the host-microbiome interface, and interkingdom signaling and the community stress response.
ncRNA-regulated immune response and its role in inflammatory lung diseases
Authors: Xie Na , Liu Gang
Published: October 2015

Despite the greatly expanded knowledge on the regulation of immune response by protein molecules, there is increasing understanding that noncoding RNAs (ncRNAs) are also an integral component of this regulatory network. Abnormal immune response serves a central role in the initiation, progression, and exacerbation of inflammatory lung diseases, such as asthma, chronic obstructive pulmonary disease, cystic fibrosis, and acute respiratory distress syndrome/acute lung injury. Dysregulation of ncRNAs has been linked to various immunopathologies. In this review, we highlighted the role of ncRNAs in the regulation of innate and adaptive immunity and summarized recent findings that ncRNAs participate in the pathogenesis of inflammatory lung diseases via their regulation of pulmonary immunity. We also discussed therapeutic potentials for targeting ncRNAs to treat these lung disorders.
Suppression of Intratumoral CCL22 by Type I Interferon Inhibits Migration of Regulatory T Cells and Blocks Cancer Progression
Authors: Anz David , Rapp Moritz , Eiber Stephan , Koelzer Viktor H. , Thaler Raffael , Haubner Sascha , Knott Max , Nagel Sarah , Golic Michaela , Wiedemann Gabriela M. , Bauernfeind Franz , Wurzenberger Cornelia , Hornung Veit , Scholz Christoph , Mayr Doris , Rothenfusser Simon , Endres Stefan , Bourquin Carole
Published: October 2015

The chemokine CCL22 is abundantly expressed in many types of cancer and is instrumental for intratumoral recruitment of regulatory T cells (Treg), an important subset of immunosuppressive and tumor-promoting lymphocytes. In this study, we offer evidence for a generalized strategy to blunt Treg activity that can limit immune escape and promote tumor rejection. Activation of innate immunity with Toll-like receptor (TLR) or RIG-I–like receptor (RLR) ligands prevented accumulation of Treg in tumors by blocking their immigration. Mechanistic investigations indicated that Treg blockade was a consequence of reduced intratumoral CCL22 levels caused by type I IFN. Notably, stable expression of CCL22 abrogated the antitumor effects of treatment with RLR or TLR ligands. Taken together, our findings argue that type I IFN blocks the Treg-attracting chemokine CCL22 and thus helps limit the recruitment of Treg to tumors, a finding with implications for cancer immunotherapy. Cancer Res; 75(21); 4483–93. ©2015 AACR.
Cabozantinib (XL184) Inhibits Growth and Invasion of Preclinical TNBC Models
Authors: Sameni Mansoureh , Tovar Elizabeth A. , Essenburg Curt J. , Chalasani Anita , Linklater Erik S. , Borgman Andrew , Cherba David M. , Anbalagan Arulselvi , Winn Mary E. , Graveel Carrie R. , Sloane Bonnie F.
Published: October 2015

Purpose: Triple-negative breast cancer (TNBC) is an aggressive breast cancer subtype that is associated with poor clinical outcome. There is a vital need for effective targeted therapeutics for TNBC patients, yet treatment strategies are challenged by the significant intertumoral heterogeneity within the TNBC subtype and its surrounding microenvironment. Receptor tyrosine kinases (RTK) are highly expressed in several TNBC subtypes and are promising therapeutic targets. In this study, we targeted the MET receptor, which is highly expressed across several TNBC subtypes.

Experimental Design: Using the small-molecule inhibitor cabozantinib (XL184), we examined the efficacy of MET inhibition in preclinical models that recapitulate human TNBC and its microenvironment. To analyze the dynamic interactions between TNBC cells and fibroblasts over time, we utilized a 3D model referred to as MAME (Mammary Architecture and Microenvironment Engineering) with quantitative image analysis. To investigate cabozantinib inhibition in vivo, we used a novel xenograft model that expresses human HGF and supports paracrine MET signaling.

Results: XL184 treatment of MAME cultures of MDA-MB-231 and HCC70 cells (± HGF-expressing fibroblasts) was cytotoxic and significantly reduced multicellular invasive outgrowths, even in cultures with HGF-expressing fibroblasts. Treatment with XL184 had no significant effects on METneg breast cancer cell growth. In vivo assays demonstrated that cabozantinib treatment significantly inhibited TNBC growth and metastasis.

Conclusions: Using preclinical TNBC models that recapitulate the breast tumor microenvironment, we demonstrate that cabozantinib inhibition is an effective therapeutic strategy in several TNBC subtypes. Clin Cancer Res; 22(4); 923–34. ©2015 AACR.