bluuebunny/crossref_metadata_2025 huggingface dataset:
PTFE Distribution in High-Temperature PEM Electrodes and Its Effect on the Cell Performance
Authors: Mack Florian , Morawietz Tobias , Hiesgen Renate , Kramer Dominik , Zeis Roswitha
Published: October 2013

A conventional high-temperature polymer electrolyte membrane (HT-PEM) fuel cell electrode primarily consists of carbon-supported platinum catalyst and nonconductive binder PTFE. Morphology and topography of the electrodes were determined with scanning electron microscopy (SEM), and local surface conductivity measurements of the electrode surfaces were done with atomic force microscopy (AFM). Particle size distribution on the electrode surface was investigated and single PTFE particles in the catalyst layer were resolved. A great influence of the PTFE content in the electrodes on the performance of membrane electrode assemblies (MEA) was observed in single cell experiments. Reducing the PTFE content resulted in a decrease of the internal resistance of the MEA and improvement of the phosphoric acid uptake and its distribution in the cell. Both properties helped enhance the fuel cell performance.
Visualizing Bubble Flows in Electrolyzer GDLs Using Microfluidic Platforms
Authors: Arbabi Faraz , Kalantarian Ali , Abouatallah Rami , Wang Rainey , Wallace James , Bazylak Aimy
Published: October 2013

In this study, microfluidic platforms were used to visualize air bubble transport in two-dimensional (2D) representations of gas diffusion layers (GDLs) to gain insight into how the geometrical features of the GDL impact multiphase flow in polymer electrolyte membrane (PEM) electrolyzers. Two dimensional porous networks were designed using volumetric pore space information, such as average porosity and average throat size obtained from micro-computed tomography (micro CT) visualizations. Microfluidic chips were fabricated to represent felt, paper, and sintered powder GDLs and used to simulate the transfer of oxygen bubbles generated at the catalyst layer, through the GDL towards the flow channels of a PEM electrolyzer. The results of this work indicate that microfluidic platforms for evaluating PEM electrolyzer GDLs is highly promising.
Effects of a New Electrochemical Cleaning Protocol on Ru@Pt Core-Shell ORR Catalysts
Authors: Jackson Ariel , Viswanathan Venkat , Forman Arnold J. , Nørskov Jens , Jaramillo Thomas Francisco
Published: October 2013

It is common to electrochemically cycle catalysts prior to testing to remove contaminants that are left on the surface of the catalysts due to synthesis or exposure to ambient atmosphere. We discuss a new electrochemical pretreatment cleaning protocol for ORR catalysts that cycles the catalysts to higher potentials. We demonstrate this procedure on a class of Ru@Pt core-shell catalysts that we have recently developed. After the new cleaning protocol, the Ru@Pt catalysts show a 30mV improvement in halfwave potential, and changes in the baseline nitrogen CVs. The changes in the baseline CVs indicate a more complete removal of surface contaminants and atomic restructuring, both of which could account for the improved activity. Additionally, we show that inaccuracies in measurements of the electrochemical surface area by Hupd are rectified by the new cleaning protocol.
The Effect of Relative Humidity on Chemical Degradation of Styrene Based Radiation Grafted Membranes in the PEFC
Authors: Zhang Zhuoxiang , Buchmüller Yves , Schmidt Thomas J. , Wokaun Alexander , Gubler Lorenz
Published: October 2013

The chemical degradation of styrene based radiation grafted membranes has been investigated by testing the MEAs at 50% RH for 110 h and different current densities. Post-test analysis using FTIR spectroscopy was performed to qualitatively and quantitatively analyze membrane degradation. The results show that higher water content in the MEA leads to a higher degradation rate of styrene based radiation grafted membranes. A range of working hypotheses is discussed from the point of view of both formation rate of reactive intermediates and chain degradation mechanism of ionomers. The strong relative humidity dependency of membrane conductivity causes the poor performance in the fuel cell when the membrane is dry. Imbalanced humidification of reactant gases (e.g. 50% at cathode and 100% at anode) can decrease chemical degradation of styrene based radiation grafted membranes, meanwhile maintaining a fuel cell performance comparable to that under fully humidified conditions.
Degradation Induced Changes in Structure-Property Relationship of Perfluorosulfonic-Acid (PFSA) Membranes
Authors: Kusoglu Ahmet , Weber Adam Z.
Published: October 2013

Perfluorosulfonic-acid (PFSA) membranes are used as the solid-electrolyte in fuel cells where they promote water transport, ionic conductivity, gas separation, and mechanical support. All of these functionalities are expected to be related to the nanostructure and chemical properties of the membrane. It is of great interest to understand how these properties change with degradation during cell operation. This study investigates the changes in water sorption and morphology of membranes that were degraded in various degradation modes based on accelerated-stress testing (AST) protocols. Our findings show that upon degradation, water uptake of the membrane decreases, which is consistent with the observed increase in its backbone crystallinity as inferred from wide-angle X-Ray scattering (WAXS) experiments. Reduced uptake accompanied by increased crystallinity in chemically degraded membranes suggests degradation-induced changes in structure-property relationship of PFSA membranes similar to annealing-induced changes.
Anhydrous Proton Conducting Hybrid Proton Exchange Membrane by Phase Mode Atomic Force Microscopy
Authors: Kwon Osung , Lee Sang C. , Lee D. H. , Sahu A. K. , Shanmugam Sangaraju , Kim M. H. , Park Sam
Published: October 2013

Hybridization of inorganic pillars and proton exchange membrane have been studied for increasing performance of proton exchange membrane fuel cell such as working under low relative humidity. For developing hybrid membrane, understanding of morphological structure is crucial. In this study, we synthesize silica meso-structured cellular foam (Si-MSU-F) and meso-structured aluminosilicate with hexagonal network (Al-MCM-41) and study morphological evolution of the membrane by using atomic force microscopy. When Nafion is composited with Si-MSU-F and Al-MCM-41, the hybrid membrane surface is evolved to different structure compare with the pristine Nafion. In addition, Si-MSU-F/Nafion shows different morphological structure as Al-MCM-41/Nafion hybrid membranes due to different hybridization mechanism between pillars and Nafion.
Atomic Force Microscopy Detection of Electronic Short-Circuits in Solid Polymer Electrolytes Fuel Cell Membranes after Accelerated Degradation
Authors: Morawietz Tobias , Hiesgen Renate , Helmly Stefan , Galm Ines , Friedrich K.Andreas
Published: October 2013

In this work we investigated Nafion® 211 polymer electrolyte membranes after 1600 h operation at open circuit voltage. With scanning electron microscopy (SEM) platinum deposition was identified inside the membrane. By investigation of cross sections with Atomic Force Microscopy (AFM) numerous platinum particles and micrometer large two-dimensional sheets of platinum particles were found across the membrane. Conductive AFM was performed to measure the electronic current across the membrane. To avoid additional ionic current contributions the measurements were performed at dry membranes in argon atmosphere with a noncatalytic gold coated AFM tip. At a few sites a steady state electronic current measured through the half cell membranes was detected that had an ohmic current-voltage polarization curve. These electric short-circuit connections, formed by platinum deposition inside the membrane, can be considered as a failure mechanisms for the fuel cell and by enhancement of radical formation may lead to formation of pin-holes.
Oxygen Transport Parameters in Nafion® 117 under Controlled Relative Humidity
Authors: Novitski David , Xie Zhong , Holdcroft Steven
Published: October 2013

Solid state electrochemical techniques have provided insight into the effect of relative humidity on oxygen mass transport properties in Nafion® 117. Specifically, subsequent potential step coulometric measurements taken over a period of time have shown that the act of measurement affects the catalyst-membrane interface. It is postulated that the formation of product water at the interface leads to interactions with the Nafion® 117 surface and results in local domain changes. This effect has been shown to be reversible provided there is adequate rest time between measurements to allow for water diffusion from the interface.
Vertically-Oriented Polymer Electrolyte Nanofiber Catalyst Support for Fuel Cells
Authors: Komini Babu Siddharth , Litster Shawn
Published: October 2013

This paper presents fabrication and characterization of a novel extended surface electrode with a high surface area catalyst support made of a polymer electrolyte composite. The degradation and high Pt loading of conventional carbon-supported Pt electrodes still present challenges for polymer electrolyte fuel cells (PEFCs). The electrode presented here is based on a high surface area Nafion composite membrane featuring vertically oriented nanofibers. Nanofibers were fabricated from solution casting SiO2/Nafion composite ionomer onto a porous polycarbonate template. A thin film of Pt was vacuum deposited directly on the surface of the nanofibers to form the electrode. Two different electrodes were fabricated: one with Pt sputtered onto the template before casting and the other with a non-sputtered template. Sputtered template electrode outperformed the non-sputtered template electrode. The structural and electrochemical characterizations show that this electrode is a viable approach.
Molecular Dynamics Study of Oxygen Permeation of Ionomer of Hydrocarbon
Authors: Sugaya Yuta , Tokumasu Takashi
Published: October 2013

Polymer electrolyte fuel cell (PEFC) is focused worldwide as the energy conversion device for next generation. However, it has never been popular because of high price and low efficiency. In cathode catalyst layer of polymer electrolyte fuel cell, an ionomer with which the catalyst is covered is very important on the point of transferring protons to the catalytic surface on the cathode side. On the other hand, it is said that ionomer interferes with oxygen permeation to the catalytic surface. The mechanism of oxygen permeation through the ionomer was not analyzed in detail because it is too small to research by experiment. In this research, we constructed the system including polymer electrolyte membrane, water molecule, oxonium ion and platinum surface by using molecular dynamics study, and researched about the effect of the water content of the ionomer on the structure of the ionomer and oxygen permeability.
Nafion-Azole-H3PO4 Composite Membranes Using Solution Processing for High Temperature PEMFCs
Authors: KIM Je-Deok , Suzuki Akira , Jun Mun-Suk
Published: October 2013

Nafion-azole-H3PO4 composite membranes were prepared by autoclave solution processing for high temperature PEMFCs. Azole molecular such as benzimidazole (bz), 1,2,3-triazole, pyrazole, imidazole, 1,2,4-triazole was used as a supporter to make much incorporation of phosphoric acid and homogeneous composite membrane between perfluorosulfonic polymer (Nafion) and phosphoric acid. The Nafion-azole-H3PO4 composite membrane was flexible. The conductivity of 0.23 and 0.01 S/cm at the temperature of 150 oC, dry was obtained at the Nafion-bz-H3PO4 and Nafion-1,2,3-triazole-H3PO4 composite membranes, respectively. The power density of 35 mW/cm2 was obtained at the Nafion-bz-H3PO4 composite membrane.
A Novel Nafion-1,2,3-Triazole - H3PO4 Composite Membrane for Non-Humidity Condition and High Temperature PEMFC
Authors: Jun Mun-Suk , KIM Je-Deok
Published: October 2013

A novel Nafion – 1,2,3-triazole – phosphoric acid (Na – Tri – PA) composite membrane was prepared by autoclave solution processing and used as an electrolyte membrane for PEMFC at non-humidity condition of 150 oC. Na – Tri – PA membrane was homogeneous. IR spectrum analysis showed the spectra of Nafion, 1,2,3-triazole, and phosphoric acid. The thermal stability of the Na – Tri – PA composite membrane increased with increasing amount of 1,2,3-triazole. For Nafion – 10% 1,2,3-triazole – 66% H3PO4 composite membrane, the maximum power density of about 30 mW/cm2 was obtained at non-humidity condition of 150 oC in the single cell performance. The electrochemical property such as EIS (electrochemical impedance spectra) and CV (cyclic voltammetry) was discussed in the single cell.
Activity of Tantalum Oxide-Based Electrocatalysts toward Oxygen Reduction Reaction for PEFC
Authors: Uehara Naoki , Ishihara Akimitsu , Kohno Yuji , Matsuzawa Koichi , Mitsushima Shigenori , Ota Ken-ichiro
Published: October 2013

Development of non-noble metal cathode is required to commercialize polymer electrolyte fuel cells. We have investigated group 4 and 5 transition metal oxide-based cathode. In this paper, tantalum oxide-based cathodes with nano-sized particles were made from oxy-tantalum phthalocyanines (TaOPc) as starting material by heat treatment under low oxygen partial pressure. The kind of catalyst supports, the oxidation temperature, and ball milling were examined to increase the oxygen reduction current. It was found that multi-walled carbon nanotube (MWCNT) was effective as catalyst support. In addition, the oxidation at 900oC under low oxygen partial pressure and ball milling were also effective to enhance the oxygen reduction activity. The maximum i
ORR current density at 0.8 V vs. RHE was about 106 mA g-1.
ORR Measurements Reproducibility Using a RRDE
Authors: Garsany Yannick , Ge Junjie , St-Pierre Jean , Rocheleau Richard , Swider-Lyons Karen
Published: October 2013

The NRL rotational drying method was used to prepare thin film Pt/C electrodes. The electrodes were characterized by the RRDE mearsurements, in which the disk curves were used for the ORR kinetic measurements and the ring curves for the H2O2 production evaluation. The reproducibility of both ring and disk currents for the ORR was investigated. It is demonstrated that RRDE methodology was highly repeatable with the use of the high quality films obtained from the rotational drying method. The results were also repeatable across laboratories, even when different measurement equipment was used, as long as attention was paid to key details about film preparation, chemical and gas purity, and cycling procedures. The rotational drying method for the RRDE measurements make it possible in getting highly reliable and reproducible performance data on the catalysts, which is crucial for the validation of the advancement in catalysts at various laboratories.
Bimodal Pt Synthesized on Heat Treated Carbon Black Support in Arc Plasma Process
Authors: NA Hyunwoong , OH JI-Won , Ji Y. , Cho Yongsoo , CHOI Hanshin
Published: October 2013

In general, furnace carbon black is used for support material thank to large specific surface area, good electrical conductivity, and chemical inertness. However, carbon corrosion degrades catalyst performance by electrically isolating detached Pt. Also, surface oxide species makes the catalyst be hydrophilic [1]. In this regard, Vulcan XC-72 carbon black was heat treated at 1,000°C, 1,100°C, and 1,200°C for 4 hours in a reducing environment in order to change crystallinity and surface properties. As the heat treatment temperature is increased, specific surface area by BET analysis is not markedly changed. However, changes of crystallinity from X-ray diffractometry, Raman spectroscopy, and high resolution transmission electron microscopy are notable. After that, Pt/C nano-catalysts are synthesized by arc plasma deposition process. Conclusively, Pt morphology can be tailored by carbon heat- treatment in the arc plasma synthesis and durable Pt/C is synthesized without post-synthesis heat treatment in liquid base synthesis.
Electrochemical Properties and Durability of Electrocatalysts Supported on SnO
2
Authors: Tsukatsune Takuya , Takabatake Yuma , Noda Zhiyun , Hayashi Akari , Sasaki Kazunari
Published: October 2013

For polymer electrolyte fuel cells (PEFCs), carbon corrosion, leading to lower activities of catalysts under cathode conditions, is one of the important technological issues to be solved. We have been developing SnO2 and Nb-SnO2 as alternative support materials. In this study, the oxygen reduction reaction (ORR) activity and the durability of Pt/SnO2 and Pt/Sn0.98Nb0.02O2 against voltage cycling between 1.0 and 1.5 VRHE are quantitatively investigated. Longer ORR durability was verified, compared to the standard catalyst, Pt/Vulcan. Furthermore, we have found that the degradation mechanism of ORR is probably different between carbon black and SnO2-based supports. In the case of SnO2-based catalysts, degradation arose mainly from the loss of electrochemical surface area (ECSA), while other factors were also involved for Pt/Vulcan. Consequently, SnO2 is a promising candidate electrocatalyst support material to solve carbon corrosion problems of PEFCs.
Pt/NbC-N Electrocatalyst for Use in Proton Exchange Membrane Fuel Cells
Authors: Stamatin Serban Nicolae , Skou Eivind Morten
Published: October 2013

A new type of fuel cell catalyst support has been synthesized and platinized. Nitrogen doped niobium carbide has been synthesized by an urea glass route. Mean particle diameter from 30-80 nm was obtained by modifying the ratio between the metal chloride and urea. Platinum nanoparticles with 3-4 nm particle diameter have been synthesized and subsequently deposited on the support using a segregation agent. X-ray diffraction confirmed the support’s structure and the presence of Pt with nanometric crystallites. Morphological characterization and elemental analysis was done by an EDS coupled SEM. The final product was characterized in an electrochemical cell in order to show that the Pt is active towards the electrochemical reduction of oxygen. The material was tested for its electrochemical stability in an acidic environment and compared against a commercial Pt based catalyst.
Deterioration Behavior of Pt in a Pt/Au Nanoparticle-Loaded Carbon Black Catalyst Analyzed by an Accelerated Durability Test
Authors: Okada Kohei , Chiku Masanobu , Higuchi Eiji , Inoue Hiroshi
Published: October 2013

Au nanoparticles with 2.5 ± 0.5 nm in size were prepared on carbon black by bubbling CO as a reducing agent in a KAuCl4 aqueous solution containing glutathione as a stabilizer (Au-G/CB). The Au nanoparticles after heat treatment (Au-G/CB-HT) had the mean particle size and size distribution of 2.8 ± 0.5 nm. Pt monolayer was deposited on the Au nanoparticles by underpotential deposition and the following galvanic replacement (Pt/Au-G/CB-HT). The activity per unit mass of Pt for oxygen reduction reaction for the Pt/Au-G/CB-HT at 0.9 V was ca. 6 times as high as that of commercial Pt/CB. In durability tests, the Pt/Au-G/CB-HT/GC electrode was more stable than commercial Pt/CB electrode. The decrease in electrochemical surface area of Pt for the Pt/Au-G/CB-HT during the initial 2000 cycles was caused by both anodic dissolution of Pt into the electrolyte solution and formation of solid solutions of Pt and Au, while after 2000 cycles it was significantly suppressed.
Pulse Laser Deposition and Sputtering of Carbon-Free Pt/SnO2 Electrocatalysts for PEFC
Authors: Higashi Takahiro , Noda Zhiyun , Hayashi Akari , Sasaki Kazunari
Published: October 2013

Polymer electrolyte fuel cells (PEFCs) are one of the promising future power sources. Even though technologies for PEFC are mostly developed, durability of their electrocatalysts is one of the most important issues for further development. In order to improve the durability against carbon corrosion problem, we have been working on carbon-free Pt electrocatalysts using SnO2 and demonstrating improved durability. However, SnO2-supported electrocatalysts often result in lower performance mainly due to relatively high contact resistance between SnO2 particles. In this study, an attempt has been made to develop an alternative way to fabricate the SnO2-based cathode using pulse laser deposition (PLD) and ion plasma sputtering in order to reduce the contact resistance. Consequently, the use of the doped-SnO2 thin layer has lowered the overpotential of cathode reactions, resulting in successful development of PEFC consisting of SnO2-supported cathode with both high power performance and durability.
Modification of Cathode Catalyst to Improve PEFC Cell Performance under Low Relative Humidity
Authors: Nakajima Hitoshi , Matsutani Koichi
Published: October 2013

Here we report several trials to modify cathode Pt catalysts to improve fuel cell performance under low relative humidity. First approach was to introduce hydrophilic group such as organic sulfonic group to Pt catalyst. The effect of the content of sulfur in cathode catalyst on the cell voltages at RH=31% was examined. Several samples of modified catalysts exhibited better cell voltages than the base catalyst. Nevertheless, the modified catalysts containing excess amount of organic sulfonic group exhibited lower cell voltage at dry condition. The cell voltages were different among the catalysts whose contents of sulfur were almost the same. It indicated that the condition other than the content of organic sulfonic group also affected the cell performance under the lower humidity.
Applicability of a Channel Flow Double Electrode as a Quantitative Monitoring Method of Pt Dissolution under Potential Cycling
Authors: Wang Zhongqi , Tada Eiji , Nishikata A.
Published: October 2013

Sub-monolayer dissolution of Platinum (Pt) nanoparticles under potential cycling is specified by a channel flow double electrode (CFDE). Dissolution of Pt2+ starts at 0.6 V (vs. SHE) in anodic scan. The dissolved amount of Pt2+ below 1.0 V is calculated using the collector current (I
C) and confirmed by ex-situ inductively coupled plasma mass spectrometry (ICP-MS). Above 1.2 V, Pt dissolution is identified as Pt4+. The amount of Pt2+ and Pt4+ dissolved in different potential regions within one cycle of CV is quantified by the I
C for the first time. An in-situ system, capable of quantitatively monitoring sub-monolayer dissolution of Pt2+ and Pt4+, is established.
Performance of PdRu/C Anode Catalyst for Anion-Exchange Membrane Direct Ethanol Fuel Cell
Authors: Ma Liang , Hsu Andrew , Chen Rongrong
Published: October 2013

Carbon supported PdRu catalysts with various Pd:Ru atomic ratios were studied by using X-ray diffraction (XRD), transmission electron microscopy (TEM), electrochemical half-cell tests, and the anion-exchange membrane direct ethanol fuel cell (AEM-DEFC) tests. Lower onset potential and peak potential and much higher steady state current for ethanol oxidation in alkaline media were observed on the bimetallic catalysts (PdxRuy/C) than on the Pd/C, while the activity for ethanol oxidation on the pure Ru/C was not noticeable. By using Pd/C anode catalysts and MnO2 cathode catalysts, AEM-DEFCs free from the expensive Pt catalyst were assembled. The AEM DEFC using the bimetallic Pd3Ru/C anode catalyst showed a peak power density as high as 176 mW cm-2 at 80 °C, about 1.8 times higher than that using the single metal Pd/C catalyst.
New Oxygen Reduction Electrocatalysts Based on Lanthanum Manganite Oxides and Their Application to the Cathode of AEMFCs
Authors: Saito Morihiro , Takakuwa Tatsuya , Kenko Takuya , Daimon Hideo , Tasaka Akimasa , Inaba Minoru , Shiroishi Hidenobu , Hatai Takeo , Kuwano Jun
Published: October 2013

Perovskite La1-x
Sr
x
MnO3 (LS
x
M) nanoparticles supported on Ketjen Black (KB) were synthesized as the cathode of anion-exchange membrane fuel cells. To reduce the particle size of LS
x
M and to improve the dispersivity on KB, a reverse micelle method was applied by using two kinds of non-ionic surfactants, i.e. polyethylene glycol nonyl-phenyl ether and polyethylene-glycol mono-4-nonylphenyl ether. 20 wt% L0.83S0.17M/KB prepared by the latter surfactant consisted of fine nanoparticles of LS0.17M (average diameter: ca. 4.3 nm), and exhibited a higher activity for oxygen reduction reaction than 45 wt% LS0.23M/KB prepared by a co-precipitation method in our previous report. A single cell using the 20 wt% LS0.17M/KB catalyst for cathode could be stably operated and gave the maximum power density of 129 mW cm-2, which was comparable to that using a conventional 46 wt% Pt/C as the cathode (138 mW cm-2).
19F and 13C PGSTE-NMR Diffusion Study to Understand Ion Transport in Alkaline Anion Exchange Membranes
Authors: Sarode Himanshu N , Herring Andrew M
Published: October 2013

Understanding ion transport in Anion Exchange Membranes (AEMs) has been a widely researched area. In this work we have utilized the method of 19F diffusion NMR to our advantage for this purpose. Fluoride ion and hydroxide ion have similar ionic sizes which makes it as an ideal replacement for the caustic anion. In particular we have studied the effect of temperature and increasing diffusion times (Δ) on self diffusion of fluoride ions. We have also made a unique effort at measuring bicarbonate and carbonate diffusion through AEMs here.
Effect of Interfacial Structure between Micro-Porous Layer and Catalyst Layer on Water Transport in PEFC
Authors: Aoyama Yusuke , Suzuki Kengo , Tabe Yutaka , Chikahisa Takemi , Tanuma Toshihiro
Published: October 2013

Although micro-porous layers (MPLs) have a role to suppress water flooding, the mechanism has not been fully understood. We observed the cross-sectional liquid water distribution inside a cathode side MPL to clarify the effect of the MPL/catalyst layer (CL) interfacial structure on water transport in the MPL. The freezing method and cryo-SEM are used for the observation. The membrane electrode assemblies (MEAs) made by two different methods (decal transfer method and GDE method) were also used. The result showed that in the MEA prepared by the decal method, liquid water is distributed inside the MPL under the land, and at the MPL/CL interface under the gas-flow channel. In contrast, in the MEA made by the GDE method, the liquid water distributions in the MPL are similar both under the land and channel. These results indicate that interfacial structure has a strong effect on liquid water distribution in the MPL.
Rationalizing Catalyst Inks for PEMFC Electrodes Based on Colloidal Interactions
Authors: Shukla Shantanu , Bhattacharjee Subir , Secanell Marc
Published: October 2013

A preliminary kinetic model was developed for polymer electrolyte membrane fuel cell (PEMFC) catalyst inks in order to understand their particle stability. The Derjaguin Landau Verwey Overbeek (DLVO) model containing van der Waals attractive and electrostatic repulsive interaction energy was applied to the aqueous ink dispersions, while a modified DLVO type interaction containing a Coulombic term instead of the electrostatic term was applied to the non-aqueous dispersions. Solvents were compared based on their particle size distribution and stability ratios. Results show that the carbon black particles are stable in a higher dielectric medium whereas they tend to aggregate in a lower dielectric medium. A low ionic concentration for the aqueous medium also helped to improve the ink stability by providing a better electrostatic particle repulsion. Experiments conducted with ethyl acetate, iso-propanol and deionized water agree with the model predictions.
Enhancement of Oxygen Reduction Activity of Zirconium Oxide-Based Cathode for PEFC
Authors: Yin Shihong , Ishihara Akimitsu , Kohno Yuji , Matsuzawa Koichi , Mitsushima Shigenori , Ota Ken-ichiro , Matsumoto Masashi , Imai Hideto
Published: October 2013

In order to develop a non-precious metal cathode for PEFCs, we have tried Zr oxide based materials. To synthesize fine particles, we used oxy-zirconium phthalocyanine (ZrOPc) as a starting material. ZrOPc was placed on multi-walled carbon nanotube (MWCNT) and treated under 0.005～0.5%O2 + 2%H2 – N2 and 4%H2 – N2 atmosphere at 900oC. The slow scan voltammetry (SSV) was performed to evaluate the catalytic activity for the oxygen reduction reaction (ORR) under nitrogen and oxygen atmosphere separately in 0.1 mol dm-3 H2SO4 at 30oC. The XRD analysis of these catalysts showed tetragonal ZrO2. The particle size was about 10 nm. The maximum ORR current was up to 300 mA g-1
Cat / C
at 0.8 V. This value was 300 times higher than Zr-CNO(CN) we reported before.
The Role of Oxygen Functionalities for Enhanced Oxygen Reduction Activity in Carbon Nanotubes
Authors: Oktaviano Haryo S , Wong Raymond A , Waki Keiko
Published: October 2013

The role of functional groups for the enhanced oxygen reduction activity in the multiwalled carbon nanotubes (MWNT) was investigated on defective MWNTs (DMWNTs). DMWNTs were prepared by chemically drilling the MWNT to modify the structure and content of functional groups on MWNT. Following cyclic voltammetry studies between the as prepared and after Ar annealed DMWNT, it is shown that even with very few quinone-functionalities present, the pre-wave (first 2e- reduction), which is believed to be quinone-mediated ORR is still remained. This result suggests that the exact mechanism on the ORR in alkaline media still not well understood. The actual content of quinone functionalities together with the presence of defects may be the key for ORR activity in alkaline media.
Nitrogen-Doped Carbon Nanotubes Prepared at Different Temperatures for Oxygen Reduction Reaction
Authors: Li Hengyi , Cheng Xuan , Weng Fang-Bor , Su Ay
Published: October 2013

The nitrogen-doped carbon nanotubes (N-CNTs) were synthesized by chemical vapor deposition using a solution containing ethanediamine and ferrocene with the four selected reacting temperatures of 800 ºC, 850 ºC, 900 ºC and 950 ºC. The temperature-dependent morphologies, microstructures, compositions and electrocatalytic activities of the CNTs were examined by SEM, TEM, XPS, Raman and electrochemical measurements. The excellent catalytic activity toward oxygen reduction reaction (ORR) in sodium hydroxide solutions was obtained with the N-CNTs prepared at 800 ºC due to the largest amount of nitrogen being doped into CNTs mainly in the form of pyridinic type nitrogen, while poorer with the N-CNTs prepared at 900 ºC as it is close to the crystal phase transformation temperature of iron. The yield of the N-CNTs increased with the increase of temperature. The growth of N-CNTs was affected by the amounts of nitrogen aggregated within the bamboo joints.
Mechanical Characterization of Anion Exchange Membranes
Authors: Vandiver Melissa A , Caire Benjamin R , Waldrop Krysta , Herring Andrew M , Liberatore Matthew W
Published: October 2013

Alkali anion exchange membrane (AEM) fuel cells have the potential for electrochemical energy conversion using inexpensive catalyst and a variety of fuel types. Stability and transport must be improved in AEMs before these devices can be fully realized. Mechanical failure of the membrane can contribute to failure of the fuel cell, thus membrane durability is critical to overall system design. Compared to well researched proton exchange membranes, there is no standard baseline AEM to compare mechanical properties. This work attempts a fundamental study of the mechanical properties of three well-established AEMs using a modified extensional rheometer platform that simulates tensile testing using small membrane samples. The limitations of using this instrument for tensile tests with brittle polymers are also discussed.
In Situ Mapping of Electrode Potential in a PEMFC
Authors: Hinds Gareth
Published: October 2013

An overview is given of the use of reference electrodes in polymer electrolyte membrane fuel cells (PEMFCs). The two most common types of reference electrode employed in PEMFCs are the reversible hydrogen electrode and the dynamic hydrogen electrode, which have the advantage of minimizing chemical contamination of the fuel cell. Conventional configurations include internal reference electrodes, which are constructed by sandwiching the electrode between two membranes, and external reference electrodes, which are typically connected to the edge of the membrane via a salt bridge. A recent breakthrough is the development of an innovative reference electrode array with a through-plate configuration, which makes possible for the first time accurate mapping of the variation in electrode potential across the active area of an operating PEMFC. This configuration overcomes the major limitations of conventional fuel cell reference electrodes in that ohmic drop, potential distribution and electrode edge effects in the membrane are negated.
Numerical Model of Polymer Electrolyte Membrane Fuel Cell Startup and Shutdown
Authors: Maranzana Gael , Lamibrac Adrien , Dillet Jérôme , Abbou Sofyane , Didierjean Sophie , Lottin Olivier
Published: October 2013

This paper presents a model aiming to simulate startups and shutdowns of Polymer Electrolyte Membrane Fuel Cells, i.e. operation stages where a hydrogen-air front is propagating in the anode compartment from inlet to outlet. This 2D model is based on a 1D generic electrode model which kinetic and mass transport parameters were fitted by comparison with voltammograms, polarization curves and CO2 emissions. This simulation tool yields results that are very close to experimental data measured using a segmented cell. It can be used to better understand degradation mechanisms linked with hydrogen starvation events or to explore different mitigation strategies
Time Evolution of Local Potentials during PEM Fuel Cell Operation with Dead-Ended Anode
Authors: Abbou Sofyane , Dillet Jérôme , Spernjak Dusan , Mukundan Rangachary , Fairweather Joseph D. , Borup Rod L , Maranzana Gael , Didierjean Sophie , Lottin Olivier
Published: October 2013

We present experimental results obtained with a 2D segmented cell with reference electrodes along the gas channels, used to record local anode and cathode potentials. Aging protocols consisting of repeated dead-end operation sequences were performed to assess the impact of hydrogen starvation on the local fuel cell performance. We observed strong local cathode potential excursion, as well as non-uniform ECSA losses and performance degradation along the cell area. The damage was more pronounced in the regions suffering the longest from fuel starvation: i.e. close to the exit of the anode compartment.
Real Time Measurement of Water Transport in Polymer Electrolyte Fuel Cell
Authors: Shimokawa Ryosuke , Nagai Hidekazu , Sugesawa Yukihiro , Minakuchi Hisashi , Sudoh Masao
Published: October 2013

Water management is a crucial aspect in operating a polymer electrolyte fuel cell. The dynamic behaviors of the water transport coefficient and electric potential were obtained from experiments. The real-time water transport coefficient α was observed by measuring the relative humidity of the inlet and outlet gases. The α passed through three steps from start-up to shut-down. The steady state α increased with increasing oxygen gas flow rate due to the water generated in the cathode catalyst layer more significantly exhausted into the gas channel and the effect of back diffusion was limited. The degradation of the performance at the higher transport coefficient might be due to the dehydration of the anode side of the membrane. During the start-up process, a potential undershoot was observed. Based on the result of the real-time α measurement, the anode side gradually was hydrated and the membrane resistance decreased because the water moved from the cathode to the anode. In the load change experiment, the peak value of αa after the load change and the potential undershoot decreased with increasing current of the first step. It was expected that the anode side was more dehydrated by the load change at a lower current in the first step. Finally, the experimental α at a steady state was in good agreement with the simulated results.
Influence of Transition Metal on Oxygen Reduction Activity of Metal-Nitrogen-Carbon Electrocatalyst
Authors: Ganesan Selvarani , Leonard Nathaniel , Calabrese Barton Scott
Published: October 2013

Iron-based metal nitrogen carbon (MNC) catalysts are produced by high-pressure pyrolysis of carbon and melamine with varying amounts of iron acetate in a closed, constant-volume reactor. The optimum amount of Fe (1.2 wt%) in MNC catalysts is established through oxygen reduction reaction (ORR) polarization. The amount of Fe retained in MNC catalysts after leaching is determined from UV-Vis spectroscopy. MNC catalysts are also prepared in the absence of one of the reaction constituents, particularly the nitrogen and iron sources, to understand the ORR active sites.
Phenylenediamine as a Promising Ligand for Non-Noble Metal ORR Catalysts
Authors: Gharaibeh Samar , Birss Viola
Published: October 2013

This paper compares the use of o-phenylenediamine (oPDA) and its polymeric counterpart, poly-o-phenylenediamine (PoPDA), as the ligand precursors for the formation of non-precious metal (NPM, Co vs. Fe) cathode catalysts. Rotating ring disk electrode (RRDE) work revealed that high onset potentials (0.92 V vs. RHE) and low %H2O2 yields (0.5 % over a wide potential range of 0.05-0.7 V) can be obtained. The use of PoPDA proved to be a better C-N source than the o-PDA monomer, likely due to the formation of a higher number of active sites or to the improved stability of these active sites on the carbon support during high temperature pyrolysis. In all cases, the Fe-based catalyst is superior to the Co-based one. Also, this study confirms the additional benefits of using acid-leached vs. as-received carbon as the support material.
In-Situ Measurement of Oxygen Partial Pressure in the Cathode Flow Field with a Hydrophilic Surface
Authors: Hirano Shinichi , Potocki Michael , Saloka George , Palluconi Steve , Crafton James
Published: October 2013

Cathode oxygen concentration is vital for the performance of proton exchange membrane fuel cells (PEMFC). A novel method to directly detect oxygen partial pressure in the cathode flowfield has been developed utilizing fluorophore molecules which are sensitive to oxygen quenching. A platinum porphyrin based fluorophore is used with a polymer binder to form the fluorophore layer that is exposed to the cathode gas flow field in the visualization cell. In this study, poly-heptafluoro-n-butly, methacrylate-co-hexafluroisopropyl, and methacrylate (FIB polymer) were used as the binder to obtain a proper range of quenching rate. Thus, the intensity of fluorescent luminescence of this fluorophore layer covers 7 kPa to 53 kPa oxygen partial pressure concentration. Also, this material composition exhibits acceptable temperature sensitivity between 40 to 90 degrees C. The polymer binder modification described in this report enabled accurate in-situ oxygen partial pressure measurements to cover typical operating conditions of an automotive PEMFC.
Ta Modified TiO2 Supports Exhibit Exceptional Durability in Polymer Electrolyte Fuel Cells
Authors: Kumar Amod , Ramani Vijay K.
Published: October 2013

Ta modified TiO2 was synthesized using a sol-gel procedure and evaluated for use as an electrocatalyst support. Of the materials evaluated, Ta0.3Ti0.7O2 exhibited remarkably high stability under aggressive potential cycling tests designed to mimic harsh automotive drive cycles. The capacitance of the Ta0.3Ti0.7O2 support changed by 12% whereas the pseudocapacitance of a carbon benchmark changed by over 100% under identical test conditions. Pt/Ta0.3Ti0.7O2 electrocatalyst prepared by catalyzing this support showed high electrochemical stability which was attributed to a strong metal support interaction (SMSI); and fairly good performance. The stability of the catalyzed supports were evaluated by monitoring the evolution of the electrochemical surface area (ECSA) under potential cycling, loss in ECSA of Pt/Ta0.3Ti0.7O2 was found to be 35% compared to 46% for Pt/C over 10,000 load cycles. Pt/Ta0.3Ti0.7O2 showed fairly good performance: the electrochemical surface area of this electrocatalyst was 41 m2/g, while the mass activity and area-specific activities for the oxygen reduction reaction (ORR) were 62 mA/mgPt and 151 µA/cm2
Pt, respectively, as ascertained from electrochemical experiments performed on a rotating disk electrode (RDE). Based on these results, we propose that Ta0.3Ti0.7O2 is an excellent corrosion-resistant alternative to carbon as an electrocatalyst support.
Enhanced Efficiency with Autonomous Oscillations: Challenges for DAFC
Authors: Mota Andressa , Gonzalez Ernesto Rafael
Published: October 2013

Electroxidation of CO-containing hydrogen exhibited enhanced efficiency with autonomous oscillations compared to the usual steady stationary state [A. Mota, Kinetic Instabilities during Electroxidation of CO-containing Hydrogen, p. 116, LAP LAMBERT Academic Publishing, Germany (2013) and The Journal of Physical Chemistry C, 117, 12495 (2013)]. Moreover, CO-containing-hydrogen oscillating mechanism is a mimetic for autonomous oscillations during small-molecules electroxidation; therefore, the same enhanced efficiency under autonomous oscillations should be present. In this context, this contribution is dedicated to formally extend the analyses on the enhance defficiency over the oscillating electroxidation of small molecules.
Nickel-Cerium Alloys for Borohydride Oxidation
Authors: Santos Diogo M.F. , Šljukić Biljana , Amaral Luis , Macciò Daniele , Saccone Adriana , Sequeira Cesar
Published: October 2013

Nickel and nickel-cerium (Ni-Ce) alloys with different amounts of Ce (5 and 10 at.% Ce) have been prepared by arc melting and characterized by scanning electron microscopy and electron probe microanalysis based on energy dispersive X-ray spectroscopy, to investigate microstructure and to determine phase composition. Subsequently, Ni and Ni alloy-based electrodes were fabricated and studied for borohydride (BH4
-) oxidation in alkaline media by cyclic voltammetry and chronoamperometry in the temperature range 25 – 45 ºC. Preliminary results showed comparable BH4
- oxidation peak current densities obtained at three electrodes, with Ni95Ce5 electrode giving the highest current densities. Electrochemical data are modelled to obtain relevant kinetic parameters of BH4
- oxidation at these electrodes. Effect of electrolyte temperature on the evaluated parameters has been investigated as well.
Progress in Alkaline Membrane Fuel Cells and Regenerative Fuel Cells
Authors: Scott Keith , Mamlouk Mohamed , Espiritu Richard , Wu Xu
Published: October 2013

The effect of anion functional group on the conductivity and performance of alkaline anion exchange membrane fuel cells (AAEMFCs) is reported. The functional groups used were trimethyl amine (TMA), 1,4-diazabicyclo[2.2.2]octane, dimethyl sulphide (DMS), diethyl sulphide, triethyl amine and N,N,N0,N0-tetramethyl-1,6- hexanediamine. Membranes and ionomer were characterised in terms of ionic conductivity and separate anode, cathode and cell performances. TMA functionalised (LDPE-co-VBC) or PVBC offered the highest conductivity amongst the various selections of amine/sulphide-based functional groups with conductivities values up to 0.25 (in plane) and 0.043 S cm-1 (through plane). Sulphide-based groups showed lower stability with temperature in comparison to amine-based groups. The increase in length of the chain in the aryl group (for example from methyl to ethyl) attached to the nitrogen (amine) or sulphur (sulphide) led to lower conductivity. TMA functionalised ionomer provided an improved oxygen reduction reaction with exchange current density some 300 times higher than that with DMS. TMA functionalized electrodes showed superior cell performance in comparison to the other functional groups with a current density of 0.72 A cm-2 at 0.6 V and a peak power density of 478 mW cm-2. The membrane exhibits good long term stability at temperatures up to 70°C. A study of a regenerative fuel cells with alkaline anion exchange membranes with CuxMn0.9−xCo2.1O4 (CuMnO) catalysts gave promising performance using a quaternary OH- ion ionomer binder based on polymethacrylate. Satisfactory stability of the membrane electrode assembly was observed from chronocoulometry.
Water Electrolysis with a Homogeneous Catalyst in an Electrochemical Cell
Authors: Bonino Christopher , Concepcion Javier , Trainham James , Meyer Thomas , Newman John
Published: October 2013

[Ru(Mebimpy)(bpy)OH2]2+[Mebimpy=2,6-bis(1-methylbenzimidazol-2-yl)pyridine; bpy =2,2’-bipyridine], a homogeneous molecular catalyst for water oxidation, is examined using an electrochemical flow cell. A homogeneous catalyst can reduce corrosion by operating at near-neutral pH and is easy to replace when degraded. Traditional alkaline electrolyzers are not free of these issues. The electrochemical flow cell, which is based on a fuel-cell design, includes a zero-gap configuration to minimize ohmic losses. The homogeneous-catalyst kinetics is elucidated by means of electrochemical methods, including Tafel plots. Current efficiencies are measured from the evolved gases. Relationships between catalyst performance and concentration, and anode material are discussed.
CuCl/HCl Electrolyzer Kinetics for Hydrogen Production Via Cu-Cl Thermochemical Cycle
Authors: Hall Derek M. , Schatz Rich S. , LaRow Eric G. , Lvov Serguei N.
Published: October 2013

An investigation of kinetic properties of the CuCl/HCl electrolytic cell verified methods applied in this study to significantly reduce the catalyst loadings required to achieve a current density of 0.5 A/cm2 at 0.7 V. The CuCl/HCl electrolytic cell is a key component of the Cu-Cl thermochemical cycle. The economic viability of the Cu-Cl thermochemical cycle was significantly improved by reducing the platinum loading required to achieve higher current densities. Electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV) were employed to investigate overpotentials of the individual electrodes and the electrolytic cell. A laboratory scale CuCl/HCl electrolytic cell was used to verify that the catalyst loading could be reduced by 68 % and still maintain a current density of 0.5 A/cm2 at 0.7 V.
Activity and Selectivity for O2 Reduction to H2O2 on Transition Metal Surfaces
Authors: Siahrostami Samira , Verdaguer-Casdevall Arnau , Karamad Mohammadreza , Chorkendorff Ib , Stephens Ifan Erfyl Lester , Rossmeisl Jan
Published: October 2013

Industrially viable electrochemical production of H2O2 requires active, selective and stable electrocatalyst materials to catalyse the oxygen reduction reaction to H2O2. On the basis of density functional theory calculations, we explain why single site catalysts such as Pd/Au show improved selectivity over pure metals such as Au.
Morphological Stability of Sn Electrode for Electrochemical Conversion of CO2
Authors: Wu Jingjie , Harris Bradley , Sharma Pranav P. , Zhou Xiao-Dong
Published: October 2013

The morphological stability of 100 nm Sn particles as the electrode for electrochemical reduction of CO2 was studied in a full electrochemical cell at room temperature and pressure. A degradation of selectivity towards CO2 reduction, accompanied by the pulverization of Sn particles was observed during long-term measurements. During the pulverization process, the size of Sn particles decreased from ~ 100 nm to ~ 3 nm in approximately 60-hour operation. The Faradaic efficiency towards the formation of formate decreased from ~90% to ~56%. On the contrary, the Faradaic efficiency for H2 evolution increased during the measurement. The degradation of the selectivity towards CO2 reduction is primarily attributed to the decrease of the potential atthe cathode.