bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of Pt-Cu Bimetallic Alloys and Their Electrocatalytic Activities for Oxygen Reduction Reaction
Authors: Fu Shaofang , Zhu Chengzhou , Du Dan , Lin Yuehe
Published: October 2015

Finding an approach to synthesize the low cost catalysts with high activity and improved durability becomes the main challenge for the commercialization of proton exchange membrane fuel cells. The electrocatalytic performance of Pt-based catalysts could be improved significantly by accurately controlling the particle size, morphology and composition. In this work, Pt-Cu bimetallic nanofoams, composed by fused nanoparticle with ~3 nm indiameter, were synthesized using a one-step reduction method. After dealloying with nitric acid, the PtCu@Pt core-shell nanofoams exhibited excellent electrocatalytic activity and durability for oxygen reduction reaction, holding great promise in fuel cell applications.
Electrochemical Structural Stability of Au-Modified Pt Nanoparticles Prepared by Arc-Plasma Deposition
Authors: Takahashi Shuntaro , Chiba HIroshi , Todoroki Naoto , Wadayama Toshimasa
Published: October 2015

The electrochemical structural stability of Au-modified Pt nanoparticles (Au
x
/Pt100 NPs, where x is the atomic ratio of Au) was investigated. Au
x
/Pt100 samples were fabricated on a highly oriented pyrolytic graphite substrate at 773 K through sequential arc plasma depositions of Pt followed by Au. In cyclic voltammograms of Au
x
/Pt100, characteristic currents correlated to the corner and edge sites of the Pt NPs (0.13 V vs. RHE) decreased with increasing x. Electro-chemical surface area decay, observed after applying potential cycling between 0.6 and 1.0 V, clearly show that surface modification of the Pt NPs with appropriate amounts of Au atoms located at the corner and edge sites improved the structural stability of the Pt NPs.
High Formic Acid Oxidation Activity and Stability of Pd Catalyst Supported by Nanoparticle-Embedded Carbon Nanofiber
Authors: Onishi Ryo , Tsujiguchi Takuya , Osaka Yugo , Kodama Akio
Published: October 2015

A nanoparticle-embedded carbon nanofiber (PECNF) was proposed as a promising support of the Pd nanoparticle catalyst for formic acid oxidation reaction (FAOR). The nanofiber supports contained different weight and different nanoparticle were prepared by the electrospinning of polyacrylonitrile (PAN) by adding the nanoparticles, TiO2: TECNF, SiO2: SECNF and carbon black: CECNF, followed by carbonization and steam activation of the nanofiber. Cyclic voltammetry (CV) revealed a significantly high FAOR activity for the Pd/SECNF [1.00], which showed “muskmelon” like structure. Moreover, the chronoamperometory (CA) revealed a higher durability of the Pd/PECNF than that of Pd/CNF. Especially, Pd/SECNF [0.50] showed excellent durability. Based on these results, it was found that the SECNF is a promising support of the Pd for the DFAFC anode.
Structure-Controlled Rh/Sn/Pt Ternary Catalysts for Complete Oxidation Reaction of Ethanol to Carbon Dioxide
Authors: Mai Tu Phuong , Chiku Masanobu , Higuchi Eiji , Inoue Hiroshi
Published: October 2015

Sn was deposited on a Pt electrode (Sn/Pt) with the coverage of 0.23, following by the Rh deposition by different methods: random arrangement (Rh/Sn/Pt(1)) and controlled arrangement (Rh/Sn/Pt(2)). Inductive coupled plasma mass spectroscopy (ICP-MS) was used to evaluate the Sn/Rh molar ratio, which was 3 for Rh/Sn/Pt(1) and 6 for Rh/Sn/Pt(2). The ethanol oxidation reaction (EOR) activity of Rh/Sn/Pt(2) was similar to that of Sn/Pt, which was ca. 3 times as high as that of Pt. However, the EOR activity of Rh/Sn/Pt(1) was ca. 1.5 times as high as that of Sn/Pt. The onset potential of EOR for the Sn/Pt and Rh/Sn/Pt electrodes was 0.1 V and 0.2 V lower than that for the Pt electrode, respectively. The in-situ infrared reflection absorption spectroscopy (IRRAS) exhibited that, for Rh/Sn/Pt(1), the formation of acetic acid was predominant over CO2, whereas Rh/Sn/Pt(2) with lower EOR activity was superior in CO2 selectivity to Rh/Sn/Pt(1).
Investigation of Durability of MEAs at Higher Temperature
Authors: Kitamura Masahiko , Noda Zhiyun , Matsuda Junko , Hayashi Akari , Sasaki Kazunari
Published: October 2015

For the next generation polymer electrolyte fuel cell (PEFC), increase in operating temperature above 100 °C is desired in order to improve the cathode overvoltage. The objective of this study is to understand degradation phenomena of cathode catalysts by simulating Fuel Cell Vehicle’s “load cycles”, where Pt dissolution/reprecipitation reaction occurs. Standard membrane-electrode-assemblies (MEAs) made with Nafion® membrane were evaluated under increased temperature like 105 °C and also under reduced humidity condition like RH57%. As a result, comparing to the standard operating condition (80 °C and RH100%), Pt enlargement was suppressed at RH57% owing to the presence of smaller amount of water. However, degradation of Nafion® ionomer under low humidity condition led to lowering MEA performance. Furthermore, at higher temperature, in addition to Nafion® degradation, enhanced Pt enlargement was recognized and became a serious problem on MEA performance.
A FIB-SEM Study on Correlations between PEFC Electrocatalyst Microstructure and Cell Performance
Authors: Okumura Makito , Nagamatsu Yohei , Noda Zhiyun , Tachikawa Yuya , Daio Takeshi , Hayashi Akari , Sasaki Kazunari
Published: October 2015

PEFC electrocatalyst microstructure strongly influences cell performance. In this study, Nafion ionomer content in the cathode electrocatalyst layer is systematically varied to modify the electrocatalyst microstructure. Current-voltage characteristics of the membrane-electrode-assemblies are measured and then the electrocatalyst microstructure is observed by the focused-ion-beam coupled scanning electron microscopy (FIB-SEM) to examine the correlations between the 3D microstructure and the cell performance. Although technical limitation was found for FIB-SEM analysis, certain correlations were also established.
Effects of Water Structure on Proton Transport in Nafion Thin Films with Molecular Dynamics Simulations
Authors: Aochi Joji , Mabuchi Takuya , Tokumasu Takashi
Published: October 2015

Proton transport properties in Nafion thin films have been investigated using molecular dynamics simulations to characterize the nanoscopic flow phenomena in the electrode of polymer electrolyte fuel cell. Protons transfer in the ionomer by a combination of the Vehicle mechanism and the Grotthuss mechanism. In this study, the Grotthuss mechanism is described using the anharmonic two-state empirical valence bond method to evaluate quantitative proton transport within the framework of classical molecular dynamics simulations. The electrode consists of platinum-supported carbon and ionomers, and it is well known that the wettability of supported carbon depends on materials and operating environment. Our results suggested that the wettability affects morphology of the ionomer and proton transport.
Effect of Hydrophilic Micro-Porous Layer Structure on Microscopic Water Distribution and Cell Performance in PEFC
Authors: Aoyama Yusuke , Suzuki Kengo , Tabe Yutaka , Chikahisa Takemi , Tanuma Toshihiro
Published: October 2015

This paper investigated the mechanism of the hydrophilic MPL with carbon fiber (CF) to increase cell performance by comparing the cell performance and water distribution inside the MPL with different pore size and thickness. The results show that the hydrophilic thick CFMPL improves cell performance by preventing the increase of concentration overvoltage under high current density region. The direct observations by the freezing method and cryo- SEM shows that water is observed in pores of the CFMPL at the catalyst layer (CL) side, while there is no water in the thick CFMPL at the gas diffusion layer (GDL) side. This suggests that the hydrophilic thick CFMPL evaporates water in the CFMPL before the water reaches to the GDL side by the large pores and the adequate thickness of the CFMPL, resulting in better anti-flooding performance.
Analysis of Cathode Catalyst Layer Structure and Oxygen Transport Resistance Depending on Fabrication Condition in PEFC
Authors: Tabe Yutaka , Akabori Sho , Hayashi Tomoya , Suzuki Kengo , Chikahisa Takemi
Published: October 2015

For efficient use of Pt catalyst in polymer electrolyte membrane fuel cells (PEFCs), the effects of the cathode catalyst layer (CL) structure on the cell performance were evaluated experimentally. In particular we focused on two parameters used in analysis by agglomerate models, the agglomerate size and the oxygen dissolution resistance to the ionomer surrounding the carbon agglomerate. Various ratios of ionomer to carbon were selected as the CL fabrication condition with same amount of Pt-supported carbon. To estimate the agglomerate size, pore size distribution (PSD) was measured by nitrogen physisorption method, and an estimation method of agglomerate size distribution from the measured PSD was applied. It was shown that the model analysis using the estimated parameters with relatively-small agglomerate size can well simulate the measured IV characteristics, and that the balance of the oxygen diffusion and dissolution resistances in the ionomer dominates the cell performance under the condition here.
Comparison of Electrocatalytic Properties of PtCo/Graphene Catalysts for Ethanol, Methanol and Borohydride Oxidation
Authors: Kepeniene Virginija , Tamasauskaite-Tamasiunaite Loreta , Antanaviciute Kornelija , Balciunaite Aldona , Norkus Eugenijus
Published: October 2015

In this study the graphene supported PtCo catalyst with the Pt:Co molar ratio equal to 1:7 was fabricated by means of the rapid microwave heating method with the aim to use it in an alkaline fuel cells, using ethanol, methanol and borohydride as fuel. It was found that the PtCo/GR catalyst with an average particle size of ca. 1-3 nm was synthesized by means of microwave heating of Pt(IV) and Co(II) salts in ethylene glycol solutions. The PtCo/GR catalyst shows an enhanced activity towards the oxidation of H2 generated by catalytic hydrolysis of BH4
– and direct oxidation of BH4
– ions as well as methanol and ethanol oxidation as compared with that at the graphene supported bare Co and Pt/C catalysts. It should be noted that the electrocatalytic activity of the PtCo/GR catalyst depends on the type of fuel.
Electrocatalyst for Direct Alcohol Fuel Cells
Authors: Cremers Carsten , Jurzinsky Tilman , Bach Delpeuch Antoine , Niether Christiane , Jung Florina , Pinkwart Karsten , Tübke Jens
Published: October 2015

The direct conversion of methanol in acidic environment at platinum ruthenium catalysts is the standard process in today’s direct methanol fuel cells. The high cost related to the relative high platinum loading and the user reluctance to use methanol hinder a wider market spread of this otherwise quite mature technology. Therefore catalysts for the alcohol conversion in alkaline environment were investigated allowing reducing the use of platinum group metals. In addition the use of other alcohols as fuel was investigated in both alkaline and acidic environment including high temperature polymer electrolyte fuel cell conditions. It will be shown that palladium is a good catalyst for the alcohol oxidation in alkaline environment if alloyed with other metals. It will further be shown rhodium as alloying metal can enhance ethanol oxidation in an acidic environment already at ambient temperature and even stronger at HT-PEMFC conditions.
Preliminary Investigation on the Electrochemical Activity of Butanol Isomers as Potential Fuel for Direct Alcohol Fuel Cell
Authors: Puthiyapura Vinod Kumar , Brett Daniel J. , Russell Andrea E , Lin Wen Feng , Hardacre Chris
Published: October 2015

A preliminary investigation of electrocatalytic oxidation activity of butanol isomers has been carried out to study their potential as fuels for direct alcohol fuel cells. The electrochemical study was carried out on Pt and Pd electrodes using a three electrode cell set up in alkaline media. The primary alcohol isomers of butanol were observed to behave similarly in their electrochemical reactions whereas 2-butanol showed completely different oxidation features on both catalysts. For example, no poisoning effects were observed for 2- butanol unlike for the primary butanol isomers. In contrast, tert-butanol did not show any oxidation reaction on Pt and Pd electrodes. Furthermore, Pd was not active at all in acidic media for butanol oxidation. The reactivity of butanol isomers were found to be in the order n-butanol>iso-butanol>2-butanol>tert-butanol based on the oxidation current density values
Synthesis of High Pd-Loaded Pd/C Catalyst Using Ultrasonic Dispersions for the Direct Formic Acid Fuel Cells
Authors: Tsujiguchi Takuya , Onishi Ryo , Osaka Yugo , Kodama Akio
Published: October 2015

In order to synthesize the high Pd-loaded Pd/C for the direct formic acid fuel cell, the ultrasonication for the Pd precursor and carbon black before the chemical reduction was conducted. It was found that the ultrasonication should be conducted for the precursor and the carbon black mixture solution. Moreover, it was found that high FAOR activity could be obtained by the ultrasonication under appropriate condition, 45 kHz 45 min in this study. Based on these results, the Pd/Cs containing 50 wt% and 80 wt% of Pd could be successfully synthesized with slight decrease in the mass activity from the Pd/C containing 20 wt% of Pd by using ultrasonication, while they could not synthesized in the case of without ultrasonication. Based on these results, the ultrasonication under appropriate condition is effective to synthesis the high Pd –loaded catalyst.
Electrocatalysis of Direct Methanol and Ethanol Oxidation in Polymer Electrolyte Fuel Cells
Authors: Aricò Antonino S. , Sebastian David , Campagna Zignani Sabrina , Baglio Vincenzo
Published: October 2015

Carbon-supported bimetallic PtRu and PtSn catalysts characterized by a high degree of alloying and metallic behavior on the surface were investigated for methanol and ethanol electro-oxidation. The variation of the coverage of adsorbed methanolic residues or the change in selectivity, in the case of ethanol electro-oxidation, with temperature were studied. For the ethanol oxidation, anode selectivity towards CO2, acetic acid or acetaldehyde was analysed in relation to both alloy and oxide contents in the catalyst. In parallel, noble metal oxides (IrOx, RuOx) and valve metal oxides (SnOx, and TiOx) were assessed as promoters for these processes. IrOx gave rise to a significant promoting effect both in the case of methanol and ethanol oxidation. Whereas, the electrocatalytic enhancement produced by the valve metal oxides was generally lower than that of IrOx and RuOx. Multifunctional catalysts appeared to provide a valid route to enhance performance and reliability of methanol and ethanol electro-oxidation processes.
Tailored DC/Sputtered Niobium Oxide Properties for PEM Electrolysis Application
Authors: Ion-Ebrasu Daniela , Enache Stanica , Rizoiu Alexandru , Filip Mihaela , Preda Silviu , Varlam Mihai , Fruth Victor , Stefanescu Ioan
Published: October 2015

Proton exchange membrane (PEM) water electrolysis is seen as one of the most efficient and simple way to obtain high purity hydrogen. A major drawback in these systems is the catalysts long term stability in aqueous media. One way to improve that is to use niobium oxides as catalytic support since they have enhanced catalytic stability and high corrosion resistance to various acid-catalyzed reactions such as sulfonated radicals in the form of proton exchange membranes. In this work we show that nano-sized niobium-niobium oxides can be obtained by DC magnetron sputtering in Ar atmosphere, without using oxygen during deposition. Residual contamination with oxygen renders the films composite, consisting of niobium-niobium oxide conglomerates resembling to a core-shell structure. The catalytic activity of the top niobium-oxide layer is investigated by voltammetric methods whereas the structural, electrical and optical properties are studied by XRD, frequency dependent impedance and UV-Vis transmission techniques, respectively.
Highly Active Ba0.5Sr0.5Co0.8Fe0.2O3-δ
Single Material Electrode towards the Oxygen Evolution Reaction for Alkaline Water Splitting Applications
Authors: Fabbri Emiliana , Cheng Xi , Schmidt Thomas J.
Published: October 2015

Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF)/carbon composite electrodes show remarkable activity towards the oxygen evolution reaction (OER). However, carbon oxidation at high potentials is definitively an issue for carbon-containing anodic electrode materials in water electrolyzers. We have recently demonstrated that after processing BSCF with carbon, the electronic structure of the material changes and high OER activity can be achieved. In this contribution we show that after processing BSCF with carbon it is possible to remove the carbon component retaining the same high OER activity of the BSCF/carbon composite electrodes, improving at the same time the electrode stability, i.e. avoiding the carbon oxidation at high potentials.
Determining the Electrochemically Active Area of IrOx Powder Catalysts in an Operating Proton Exchange Membrane Electrolyzer
Authors: Zhao Shuai , Yu Haoran , Maric Radenka , Danilovic Nemanja , Capuano Chris , Ayers Katherine E , Mustain William E
Published: October 2015

Iridium oxide is one of the most common anode catalysts in commercial PEM electrolyzers for its high oxygen evolution reaction (OER) activity and stability. Unfortunately, benchmarking iridium oxide OER catalysts has proven difficult since IrO2 cannot undergo proton underpotential deposition, which makes it difficult to estimate the electrochemically active surface area (ECSA). In this work, we propose a method to calculate the electrochemically active surface area of iridium oxide in an operating PEM electrolyzer. A constant of 601 mC/cm2 was obtained using powder electrocatalysts by correlating the pseudocapacitive charge and electrochemically active surface area of the iridium oxide. This allowed us to determine the catalyst specific and mass activities in an operating PEM electrolyzer.
PEM-Type Water Electrolysis/Fuel Cell Reversible Cell with Low PGM Catalyst Loadings
Authors: Ioroi Tsutomu , Yasuda Kazuaki
Published: October 2015

We present the synthesis and characterization of electro-conductive Magneli phase oxide supported catalysts for reversible (unitized) regenerative fuel cells (RFCs) to reduce PGM loadings in the catalyst layers. In the operation condition of RFC, carbon-based supports are not suitable because intensive corrosion during water electrolysis operations. To utilize PGM more effectively, oxidation-resistant Ti4O7-based support was examined under MEA operation conditions.
Development of a Pure Oxygen Fuel Cell System for an Autonomous Underwater Vehicle with Focus on Fuel Starvation due to Inert Gas Accumulation on the Anode
Authors: Hitscherich Manuel , Cremers Carsten , Stolten Detlef , Pinkwart Karsten , Tübke Jens
Published: October 2015

In this paper a LT-PEM fuel cell stack is used in an autonomous underwater vehicle (AUV) as a range-extender to increase its mission duration by continuously supplying the AUV with electricity. A battery buffers the difference between generated power from the fuel cell and consumed power of the AUV motor and payload. For fuel cell operation in an AUV different challenges arise linked to the surrounding sea water. These conditions lead to the design of a closed fuel cell system which will be outlined. Additionally measurements concerning a purge free dead-ended anode operation of the fuel cell stack will be presented.
Water Management in an Alkaline-Exchange-Membrane Fuel Cell
Authors: Shiau Huai-Suen , Zenyuk Iryna V , Weber Adam Z
Published: October 2015

Water management in the alkaline-exchange-membrane fuel cell (AEMFC) was investigated to gain insight into the coupling of electrochemical reaction kinetics and water transport. We developed a two-dimensional nonisothermal model that can predict the response of an AEMFC according to variations of operating parameters, such as the inlet relative humidity and temperature. The results demonstrated how the performance is enhanced with increasing anode and cathode humidification. Water management and ion-transport characteristics of an AEMFC assembly are discussed in detail. Our model can be used to examine and elucidate performance bottlenecks and enable strategies to overcome them, significantly increasing the possibility of AEMFC commercialization.
The Effect of Carbonate and pH on Hydrogen Oxidation and Oxygen Reduction on Pt-Based Electrocatalysts in Alkaline Media
Authors: St. John Samuel , Atkinson Robert W. , Roy Asa Logan , Unocic Raymond R , Papandrew Alexander B. , Zawodzinski Thomas A.
Published: October 2015

We investigated the performance of several carbon-supported RuxPty electrocatalysts for their alkaline hydrogen oxidation and oxygen reduction performance in the presence of carbonate and compared their performance with monometallic, carbon-supported Pt. Our results indicate a strong dependence of HOR upon pH for the monometallic Pt catalysts (22 mV/pH) and a weak dependence upon pH for the Ru-containing electrocatalysts (3.7, 2.5, and 4.7 mV/pH on Ru0.2Pt0.8, Ru0.4Pt0.6, and Ru0.8Pt0.2, respectively). These results are consistent with our previous findings that illustrate a change in rds from electron transfer (on monometallic Pt) to dissociative hydrogen adsorption (on RuxPty catalysts). Analysis of the kinetic currents to determine the rate-determining step via Tafel slope analysis provides additional data supporting this conclusion. There is no difference in the performance at comparable pH values in the presence or absence of carbonate on monometallic Pt indicating that water/hydroxide is the primary proton acceptor for alkaline HOR. Finally, we observe no pH or carbonate dependence for the ORR on monometallic Pt.
Cerium Migration during PEM Fuel Cell Assembly and Operation
Authors: Baker Andrew M , Torraco Dennis , Judge Elizabeth J. , Spernjak Dusan , Mukundan Rangachary , Borup Rod L , Advani Suresh G , Prasad Ajay K
Published: October 2015

In PEM fuel cells, cerium migration is influenced by proton flux,as well as gradients in electric potential, ion concentration, andwater content. These factors were investigated in ex situexperiments and in operating fuel cells. Potential-inducedmigration was measured ex situ in hydrated window cells. CeriumcontainingMEAs were also fabricated and tested under ASTs.MEA disassembly and subsequent XRF analysis were used toobserve rapid cerium migration within the MEA. During MEA hotpressing, humidification, and low RH operation at OCV, ionicdiffusion causes uniform migration from the membrane into thecatalyst layers. During high RH operation at OCV, in-plane ceriumgradients arise due to variations in water content. These gradientsmay diminish the scavenging efficacy of cerium by reducing itsproximity to generated radicals.
Effect of Hygrothermal Ageing on PFSA Ionomers' Structure/Property Relationship
Authors: Shi Shouwen , Dursch Thomas J. , Borup Rod L , Weber Adam Z , Kusoglu Ahmet
Published: October 2015

Perfluorosulfonic-acid (PFSA) membranes are frequently subjected to high humidity and temperature cycles during fuel-cell operation. It is of great interest to understand how the properties of the membrane change with ageing conditions and time. In this study, we investigate how the properties of as-received and pretreated Nafion membranes change after exposure to hygrothermal ageing, including the chemical structure, mechanical properties, water uptake, ionic conductivity, and morphology. Our findings demonstrate that anhydrides form during ageing via a condensation reaction, which results in chemical crosslinks that impair the membrane functionalities by reducing water uptake and conductivity and increasing the storage modulus and α relaxation temperature. In addition, a membrane aged in a 75% relative humidity environment exhibits more dramatic changes compared to that aged in 100% conditions. It is also shown that the impact of ageing can be recovered through a post-treatment by boiling the membrane in strong acid.
Effects of Repeated Feed-Gas Exchange Processes on Degradation Processes of Pt-Based PEFC Cathode Catalysts Studied by In-situ XAFS, STEM-EDS and Electrochemical Methods
Authors: Samjeské Gabor , Higashi Kotaro , Takao Shinobu , Sekizawa Oki , Kaneko Takuma , Nagamatsu Shinichi , Nagasawa Kensaku , Uruga Tomoya , Iwasawa Yasuhiro
Published: October 2015

Repeated anode gas exchange (AGEX) cycles and cathode gas exchange (CGEX) cycles were applied to MEAs with Pt3Co/C cathode catalysts to investigate the degradation processes and to compare with the case of Pt/C. The structural and electronic changes of the catalysts during the feed gas-exchange cycles were examined at the top position area of the MEAs by in-situ XAFS and at the top and bottom positions by STEM-EDS. The ORR performance decreased steadily by the AGEX cycles though STEM revealed neither large cracks nor voids nor detached particles in the top position area of the MEA by the AGEX cycles where the electrochemical surface area (ECSA) remained unchanged. On the other hand, neither ORR performance nor ECSA decreased by the CGEX cycles though the particle size only in the bottom position area increased a little after the CGEX treatment. In-situ time-resolved XAFS spectra at Pt LIII-edge showed a decrease of the XANES white line peak height in case of the AGEX, which is not due to particle growth.
Effects of Cobalt Cation on Low Pt-loaded PEM Fuel Cell Performance
Authors: Cai Yun , Kongkanand Anusorn , Gu Wenbin , Moylan Thomas E
Published: October 2015

Pt alloys such as PtCo are attractive as cathode catalysts in PEM fuel cell systems due to their high catalytic activities. However, in a fuel cell the non-noble metal such as cobalt can dissolve and not only cause degradation of oxygen reduction activity but can also migrate into the ionomer inducing proton conduction loss, especially at high current densities. These losses are not readily explained quantitatively using our current fuel cell model. In this study, we conducted controlled experiments where known amounts of Co cation were exchanged into membrane-electrode assemblies (MEAs). The effects of Co level on oxygen reduction activity, electrode and membrane proton conductions, and electrode oxygen transport were studied using multiple electrochemical methods on MEAs. These newly acquired results will be used to improve our current model and provide direction for future fuel cell development.
Experimental Results with Fuel Cell Start-up and Shut-down. Impact of Type of Carbon for Cathode Catalyst Support
Authors: Lottin Olivier , Dillet Jérôme , Maranzana Gael , Abbou Sofyane , Didierjean Sophie , Lamibrac Adrien , Borup Rod L , Mukundan Rangachary , Spernjak Dusan
Published: October 2015

Separate testing protocols for fuel cell startups and shutdowns were developed to distinguish between their effects on reverse currents and CO2 evolution. The internal currents and the local potentials were measured with different membrane-electrode assemblies (MEAs): we examined the influence of the type of carbon for cathode catalyst support as well as the mitigating effect of low anode Pt loading. Significant differences were observed and the experiments also confirmed previous results that the evolved CO2 accounts for less than 25% of the total exchanged charge.
Electrochemical Impedance Spectroscopy as a Diagnostic Tool for High-Temperature PEM Fuel Cells
Authors: Mack Florian , Laukenmann Ruben , Galbiati Samuele , Kerres Jochen A. , Zeis Roswitha
Published: October 2015

Electrochemical Impedance Spectroscopy (EIS) is used to investigate the impact of acid doping level, air stoichiometry, polymer membrane type, and catalyst material on the operation of Membrane Electrode Assemblies (MEA) for high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs). EIS spectra are recorded during operation and analyzed by means of an equivalent circuit model to separate the contributions of individual internal losses. Acid doping level in membrane and electrodes plays a major role for MEA performance. Air stoichiometry influences the MEA operation mainly by affecting the cathode mass transport and charge transfer losses. The investigated membrane materials have little effect on MEA performance, although differences are observed in the shapes of the EIS spectra. The use of a Pt3Co/C alloy catalyst improves the MEA performance to a record value of 707 mV at 200 mA cm-2 in the polarization curve.
The Importance of Diffusion Mechanisms in High Temperature Polymer Electrolyte Fuel Cells
Authors: Cao Qing , Beale Steven B. , Reimer Uwe , Froning Dieter , Lehnert Werner
Published: October 2015

Diffusion is an important mechanism for high temperature polymer electrolyte fuel cells. In this paper, a three-dimensional computational fluid dynamics model with different mass transfer formulations was developed and applied to an existing design. The solution of the inverted form of the Maxwell-Stefan equations (generalized Fick's law) was compared with the multi-component form of Fick's law in the channels and gas diffusion layers of a typical high temperature polymer electrolyte fuel cell. It was found that the deviation between the two sets of results was relatively small. A preliminary water transfer model was implemented to calculate the water cross over.
Resistance Measurements for Multilayer Supported Membranes
Authors: Peppin Daniel M. , Yandrasits Mike , Fochs Austin S
Published: October 2015

It is possible to characterize, separately, the through-plane resistance of the neat ionomer skin layers as well as the ionomer filled support composite layer by measuring the through-plane resistance for a series of supported membranes varying only in ionomer skin thickness. The composite layer conductivity can then be compared to the conductivity of the neat ionomer, allowing for the determination of a "conductivity restriction" factor. This conductivity restriction factor can then be compared to the volume fraction of nonconductive support material in the composite layer to determine whether the impact on conductivity is due solely to acid site dilution or if there are additional losses. This analysis can be used to compare various support materials for their impact on through-plane resistance.
Effect of Hydrophilic Treatment of Cathode Channel on Liquid Water Transport through Gas Diffusion Layer and Performance of PEFC
Authors: Nishida Kosuke , Kono Yudai , Nakamura Takuya , Giga Ryo
Published: October 2015

Water flooding and plugging in cathode of polymer electrolyte fuel cells (PEFCs) lead to severe performance degradation. The aim of this study was to investigate the effect of hydrophilization of cathode channel on the liquid water transport through the gas diffusion layer (GDL) in an operating PEFC using cross-sectional visualization technique. Furthermore, the correlation between the water behavior and the cell performance was also discussed by monitoring the cell voltage and differential pressure in the cathode channel. It was noted that hydrophilic treatment of cathode channel effectively encourages liquid water suction from GDL and alleviates water flooding near catalyst layer (CL). Moreover, hydrophilization doesn’t frequently cause water plugging inside gas channel.
In-Operando Neutron Radiography Studies of Polymer Electrolyte Membrane Water Electrolyzers
Authors: Hoeh Michael Andreas , Arlt Tobias , Kardjilov Nikolay , Manke Ingo , Banhart John , Fritz David L , Ehlert Jannik , Lüke Wiebke , Lehnert Werner
Published: October 2015

Polymer electrolyte membrane water electrolysis cells were studied using in-operando neutron radiography, revealing insights into the gas-water distribution inside the cells. Cells were operated at current densities up to 2 A/cm² and for water flow rates ranging from 0.5 ml/(min cm²) up to 5 ml/(min cm²). The averaged gas amount in the flow channels was quantified, revealing that the ratio of gas to water inside the channels decreases for an increasing water flow rate on the anode side. This examination also demonstrates that neutron radiography is very suitable to study gas/water two-phase flow phenomena in running electrolysis cells.
Carbonaceous Nanowire Supports for Polymer Electrolyte Membrane Fuel Cells
Authors: Garzon Fernando H , Wilson Mahlon S. , Banham Dustin , Ye Siyu , More Karren L.
Published: October 2015

Carbohydrate-dye combinations were used to form ionically-linked soft templates for the formation of polypyrrole nanowire networks. High yields of nanostructured products were obtained using small amounts of low-cost carbohydrate and dye template materials, the majority of which remained encapsulated within the nanowires. Varying the concentration and the two-part ratio of the templates influenced the length and diameter of the nanofiber segments within the nanowire network. Pyrolysis of the nanowires yielded carbonaceous fibers containing nitrogen heteroatoms as well as convoluted graphitic domains well suited for supporting Pt nanoparticles. The resulting high density of nucleation sites enabled the formation of smaller Pt particles compared to commercial catalysts despite significantly higher support surface loadings.
Conductivity Limits of Extrinsically Doped SnO2 Supports
Authors: Worsdale Matthew , Rabis Annett , Fabbri Emiliana , Schmidt Thomas J. , Kramer Denis
Published: October 2015

We find extrinsic conductivity of Ta-doped SnO2 electro-catalyst supports to be maximal at around 1% Ta-doping. Extrinsic conductivity is limited due to two effects: (i) limited dopant solubility due to thermodynamic competition with ternary oxides, and (ii) electron localization at the Ta center leading to collaborative Jahn-Teller distortions and a freezing out of the donor state with increasing dopant concentration.
Indium Tin Oxide as Catalyst Support for PEM Fuel Cell: RDE and MEA Performance
Authors: Wang Guanxiong , Niangar Ellazar , Huang Kan , Atienza Dianne , Kumar Amod , Dale Nilesh , Oshihara Kenzo , Ramani Vijay K
Published: October 2015

High surface area indium tin oxide (ITO) catalyst support materials were synthesized by using co-precipitation method to get uniform and small particle size. Colloidal deposition was used to deposit platinum onto the ITO support. The ITO support demonstrated exceptional electrochemical stability in RDE tests with less than 10% double layer pseudo capacitance loss compared with a 270% change for Vulcan XC-72R carbon under the standard support stability protocol (start-stop). 40%Pt/ITO catalyst showed higher durability than the commercial Pt/C when tested using the support stability protocol. The ECSA change for 40%Pt/ITO was similar to 46%Pt/C (TKK) under catalyst stability protocol (load cycling) but it showed less than 4% ECSA change compared with 40% loss for commercial catalyst under support stability protocol. The baseline mass activities (RDE) for the two catalysts (Pt/ITO and Pt/C) were similar. However, the fuel cell performance in the MEA was very poor for 40%Pt/ITO catalyst and XPS and EDX techniques revealed the formation of indium hydroxide and support degradation upon fuel cell operation, though these modes were not evident upon testing in an RDE.
Sn02 Aerogels: Towards Performant and Stable PEFC Catalyst Supports
Authors: Ozouf Guillaume , Cognard Gwenn , Maillard Frederic , Guetaz Laure , Heitzmann Marie , Beauger Christian
Published: October 2015

Carbon free catalyst support were synthetized from tin dioxide aerogels obtained after supercritical CO2 drying of gels synthetized following an acid catalyzed sol-gel route, starting from metal alkoxides precursors. Sb doping at 10 at% was realized adding antimony alkoxide to the sol. The nanoscale morphology can be controlled during the sol-gel synthesis route and is retained after drying. The effect of doping with Sb (V) on the structure and the morphology of the material was investigated by XRD, SEM and nitrogen sorption. Our materials showed reasonable specific surface areas (85 m²/g). The bimodal narrow pore size distribution, centered on around 25 and 45 nm after calcination at 600 °C, is particularly well adapted to the foreseen application. Sb doped aerogel exhibited an impressive improvement of electronic conductivity, reaching 0.13 S/cm. This is representing a 4 orders of magnitude increase compared to pure SnO2. This level of conductivity is almost equivalent to that of carbon Vulcan XC-72R measured in the same conditions (4 S/cm). These properties make SnO2: Sb a very promising material as catalyst support for PEFC cathode. Three different methods of platinum deposition on SnO2: Sb surface were studied. TEM and analysis was used to visualized Pt nanoparticles dispersion and sizes. Electrochemical features, like ECSA and ORR catalytic activities, of the best electrocalalysts in term of dispersion were investigated by the mean of RDE. Reduction by ethylene glycol method show higher mass catalytic activity than reference carbon-based electrocatlyst.
Corrosion Resistant Electrospun Niobium Carbide Nanotube Supports for PEMFC Cathodes
Authors: Nabil-Moreau Yannick , Cavaliere Sara , Harkness Ian , Hards Graham , Sharman Jonathan , Jones Deborah Jacqueline , Rozière Jacques
Published: October 2015

A synthesis route is reported based on the electrospinning technique that leads to NbC nanotubes with the appropriate properties for an electrocatalyst support for PEMFC cathode. The NbC nanotubes were successfully catalysed with 3 nm Pt particles by a microwave assisted polyol method so as to be investigated as electrocatalyst support. The accelerated stress test (AST) described in this contribution highlights the high stability of the novel NbC based support in comparison with a commercial 50 % Pt/C with similar the electrochemical surface area (ECSA).
Electrospun Ni nanofibres as Pt supports for PEMFC electrodes
Authors: Ercolano Giorgio , Cavaliere Sara , Jones Deborah Jacqueline , Rozière Jacques
Published: October 2015

Nickel nanofibres were prepared by electrospinning followed by specific thermal treatments. Pt/Ni fibrous electrocatalysts were obtained by galvanic displacement of the metal surface atoms with platinum. A novel, very fast Ni displacement assisted by microwaves is described. The Pt/Ni nanofibres were characterised for their activity towards oxygen reduction for their application in PEMFC electrodes.
Fabrication and Performance of Membrane Electrode Assembly Using a Hydrophilic Pt/[TaOPO4/VC] Electrocatalyst
Authors: Garsany Yannick , Sassin Megan B. , Gould Benjamin D. , Swider-Lyons Karen
Published: October 2015

Oxide- and phosphate-supported catalysts have been shown to promote the oxygen reduction reaction (ORR) in acid and alkaline electrolyte. We previously reported a high mass- and area-specific ORR activity for an electrocatalyst with 18 wt% loading of 2.4 nm Pt nanoparticles supported on a 3 wt% tantalum oxyphosphate-treated VC (Pt/[TaOPO4/VC]). The electrocatalyst was heat treated at 660°C in a reducing atmosphere and characterized using thin-film rotating disc electrode (RDE) in an acidic electrolyte and alkaline electrolyte. In this study, we focused on Proton exchange membrane fuel cell (PEMFC) catalyst layers (CLs) fabricated by by direct deposition of the Pt/[TaOPO4/VC] electrocatalyst as the active cathode material onto the HP Nafion® membranes using an in-house built ultrasonic spray system. We focused our attention on the addition of a surfactant (i.e. Triton X100) to the catalyst ink formulation, as it has been shown that a surfactant can improve the wetting characteristics of the ink. Performance evaluation and cross-sectional visualization of the CCMs were performed. The performance of the CCMs prepared using the Triton ink formulation is superior to the performance of the CCMs prepared using the Standard ink formulation for both for the Pt/[TaOPO4/VC] and the Pt/C electrocatalyst, especially in the high current density region.
GDL and MPL Characterization and Their Relevance to Fuel Cell Modelling
Authors: Haußmann Jan , Wilhelm Florian , Enz Simon , Klages Merle , Pournemat Anahid , Bergbreiter Christian , Clark Joseph Simon , Duraisamy Keerthi , Seidenberger Katrin , Markötter Henning , Manke Ingo , Scholta Joachim
Published: October 2015

Liquid water saturation of gas diffusion layer (GDL) pores limits gas transport leading to poor overall performance in polymer electrolyte membrane fuel cells (PEMFC). A survey of relevant parameters for GDL characterization, useful methods for investigations and the implications of these results to GDL modelling is provided. The GDL structure can be characterized using X-ray based methods. Structural information and surface parameters must be known to model the water distribution itself. Approaches for the determination of spatially resolved and integral surface property data are presented. For example, the inner contact angle can be determined by inverse gas chromatography. Other relevant parameters are the Leverett function, electrical and mechanical parameters such as E module and shear modulus G. Methods and results of the physical characterization are presented. The use of both structural and surface parameters is shown for Monte Carlo (MC) modelling describing the behavior of liquid water inside the porous fibre structure. Furthermore, these results are used to consider local changes in morphology and surface properties of the GDL and to improve full cell computational fluid dynamics (CFD) simulations of PEM fuel cells.
Impact of Cell Compression on Resistance, Mass Transport, and Ultimate PEMFC Performance
Authors: Sassin Megan B. , Garsany Yannick , Gould Benjamin D. , Swider-Lyons Karen
Published: October 2015

A balancing act in cell compression must be struck to simultaneously minimize contact resistance while maintaining the open pore network that facilitates effective mass transport in the gas diffusion layer (GDL), microporous layer (MPL), and catalyst coated membrane (CCM). While this is understood industrially in commercial PEMFCs, the impact of assembly protocols (e.g. compression) on single cell PEMFCs in research labs is not well understood or documented, and hinders the researcher’s ability to collect meaningful data on new catalysts and electrode structures. We are developing fabrication and assembly protocols for single cell PEMFCs and have systematically examined the impact of cell compression on the structures of the GDL, MPL, and in-house fabricated CCM. The loss or retention of the pore structure of those components under compression provides key evidence for the dominant cause of mass transport limitations in the PEMFC.
Influence of Hydrophilic and Hydrophobic Triple MPL Coated GDL on the Oxygen Transport Resistance in a PEFC under High Humidity Conditions
Authors: Kitahara Tatsumi , Nakajima Hironori , Okamura Kosuke
Published: October 2015

Gas diffusion layers (GDLs) coated with a hydrophobic microporous layer (MPL) have been commonly used to improve the performance of polymer electrolyte fuel cells (PEFCs). In the present study, a hydrophilic and hydrophobic triple MPL coated GDL, in which a thin hydrophilic layer was coated on the hydrophobic double MPL, was developed to achieve further enhancement of the PEFC performance under high humidity conditions. The oxygen transport resistance was determined from the limiting current density values of polarization curves to evaluate the ability of the GDL to prevent flooding. A triple MPL coated GDL, in which the polytetrafluoroethylene (PTFE) content in the hydrophobic MPL in contact with the hydrophilic layer is 20 mass% and that in the MPL in contact with the carbon paper substrate is 10 mass%, exhibits much lower oxygen transport resistance than a conventional hydrophobic MPL coated GDL.
Effect of Pore Volume of Hydrophilic Microporous Layer (MPL) on PEFC Performance
Authors: Tanuma Toshihiro , Kawamoto Masako
Published: October 2015

For the better water management in polymer electrolyte fuel cells (PEFCs), microporous layers (MPLs) are generally used. In this paper, MPLs having various pore volumes were prepared using different carbon material. The effect of pore volume of the MPL was examined on cell performance, especially the degree of flooding at the cathode. It was confirmed that pore volume of the MPL has a significant impact on the cell performance and that the hydrophilic MPL with a large pore volume is effective in reducing water flooding in the cathode catalyst layer.
In-Situ Measurement of Oxygen Particial Pressure on the Surface of a Cathode GDL with Automotive Compatible Operating Conditions
Authors: Hirano Shinichi , Chen Jixin , Potocki Michael , Saloka George
Published: October 2015

Cathode oxygen concentration is vital for fuel cell performance. In-situ measurement of oxygen partial pressure provides a method to determine the local oxygen concentration in the cathode. A novel method that uses oxygen sensitive fluorophore materials has been developed to directly measure the oxygen partial pressure in the cathode flow field during fuel cell operation. Fluorescent luminescence is sensitive to oxygen quenching as described by the Stern-Volmer equation. The oxygen quenching rate was modified to meet a desired range of oxygen partial pressure measurement. In a previous study, a fluorophore ink material with a platinum porphyrin based fluorophore dispersed in the FIB polymer was developed. This fluorophore ink material showed a sufficient level of intensity of fluorescent luminescence to cover the typical operating condition of an automotive proton exchange membrane fuel cell (PEMFC). However, this fluorophore ink material was too viscous for the surface of the gas diffusion layer (GDL) where ink material clogged the pores of the GLD and lowered the fuel cell performance. In this study, the fluorophore ink material was modified. A newly developed less viscous fluorophore ink material was confirmed that the fuel cell performance was not affected by the sprayed ink materials. Concurrently, it was confirmed that the oxygen quenching rate of this fluorophore materials were retained. The Stern-Volmer calibration enabled accurate in-situ oxygen partial pressure measurements on the surface of the cathode GDL to cover the typical operating conditions of an automotive PEMFC.
Influence of MPL Structure Modification on Fuel Cell Oxygen Transport Resistance
Authors: Lu Zijie , Waldecker James , Tam Mickey , Cimenti Max
Published: October 2015

In this work the dependence of limiting current on gas pressure and temperature was measured to separate the oxygen transport resistance into its components: molecular diffusion resistance in the gas diffusion layer (GDL) and resistance in the catalyst layer (CL), which comprises Knudsen diffusion resistance and oxygen permeation resistance through ionomer. The effect of microporous layer (MPL) modification by laser perforation on the oxygen transport resistances was investigated. The resistance in CL contributed a significant portion, about one quarter, to the total oxygen transport resistance. A trend of decreasing CL resistance with increasing temperature was observed. This temperature effect was mainly attributable to the oxygen permeation in CL ionomer. The MPL modification had little influence on the total transport resistance as well as its individual component for the cells under dry operation, while the perforated MPL significantly reduced the transport resistance when water starts to condense in electrode. This finding indicated that the MPL plays important roles in the cathode water management.