bluuebunny/crossref_metadata_2025 huggingface dataset:
A Versatile Preparation of Highly Active ZIF-Based Non-PGM Catalysts through Solid State Synthesis
Authors: Zhao Dan , Shui Jianglan , Grabstanowicz Lauren , Liu Di-Jia
Published: September 2014

Current proton exchange membrane fuel cell uses precious metal such as platinum as the catalyst to promote electrochemical reactions at both electrodes, which presents a significant cost barrier for large scale fuel cell commercialization. To replace precious metal with other low cost, earth-abundant materials represents a critical yet incredible challenging area in future fuel cell research. To compete with the precious metal based catalyst, the non-platinum group metal (non-PGM) materials must have higher active site density and improved turn-over-frequency. In this report, we discuss a new method of preparing “support-free”, low-cost non-PGM catalysts produced by using “one-pot” synthesized metal-organic frameworks. The new approach led to the formation of catalysts with high-density of active site and high efficiency towards the oxygen reduction reaction in the acidic medium, measured by rotating disk electrode in oxygen saturated electrolyte and under single fuel cell operating condition.
Development of Pt-Free Carbon-Based Catalyst for PEFC Cathode Prepared from Polyacrylonitrile
Authors: Chokai Masayuki , Daidou Takahiro , Nabae Yuta
Published: September 2014

Carbon-based catalyst for PEFC cathode was prepared from polyacrylonitrile (PAN) by adopting the PAN-based carbon fiber chemistry. The PAN prepared on radical polymerization was stabilized in air. The stabilized PAN was pyrolyzed in nitrogen. Finally the carbon-based catalyst was obtained after activation in ammonia. On half cell testing with rotating disc electrode (RDE) measurement, the catalyst prepared with appropriate amount of Fe species in pyrolysis process showed high oxygen reduction reaction (ORR) activity. Additionally, a membrane electrode assembly comprising of the carbon-based catalyst as cathode catalyst was prepared and its PEFC performance has been also demonstrated.
Improved Cathode Catalyst Layers for Proton Exchange Membrane Fuel Cells
Authors: Jayasayee Kaushik , Zlotorowicz Agnieszka , Clos Daniel Perez , Dahl Oaystein , Thomassen Magnus Skinlo , Dahl Paul Inge , Kjelstrup Signe
Published: September 2014

In this work we show how two different catalyst layer fabrication techniques can improve the PEM fuel cell performance by introducing macro porosities in the layer. In the first technique, a template with 4 μm diameter pillars made using photo lithography is pressed against the cathode side of Gore® Primea® MEA to create evenly distributed macro pores/channels. In the other technique, mono-dispersed polystyrene particles with 1 μm diameter were used as pore formers to obtain homogeneously distributed macropores in the cathode catalyst layer. These MEAs were made in-house with the cathode catalyst layer thicknesses of about 1 μm. Fuel cell testing carried out on these two types of modified MEA structures with lower Pt utilization show a reasonable improvement in the cell performance at higher current densities. The improved performance at high current densities could be attributed to the presence of macro porosities in the catalyst layer, which enhance the mass transport properties of the catalyst layer.
A New CCM/MPL Structure for High Power Density Polymer Electrolyte Fuel Cells
Authors: Park Jaehyung , Pasaogullari Ugur , Bonville Leonard J.
Published: September 2014

A new catalyst coated membrane (CCM)/micro-porous layer (MPL) structure, which eliminates the carbon paper or cloth as a macroporous substrate was developed for a high limiting current density polymer electrolyte fuel cell. The MPL was fabricated directly on the CCM, forming an integrated gas diffusion layer (GDL). The goal of the MPL deposited on both sides of the CCM is to reduce both mass transport and contact resistance losses and improve fuel cell performance at very high current densities. Spray deposition with a heated plate was used for depositing a commercial CCM with the MPL. The results show that a porous structure was produced in the deposited MPL layer, which results in open pathways for fuel and oxygen to a catalyst layer (CL). No evidence of damage to the CCM during the spray deposition was observed.
Influence of GDL Coated with MPL Containing CNTs on PEFC Performance Under Low and High Humidity Conditions
Authors: Kitahara Tatsumi , Nakajima Hironori , Okamura Kosuke
Published: September 2014

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 GDL coated with an MPL containing hydrophilic carbon nanotubes (CNTs) was developed to achieve further enhancement of the PEFC performance under both low and high humidity conditions. The less hydrophobic pores formed primarily by the CNTs are effective at conserving the membrane humidity, which enhances the performance under low humidity conditions. The MPL containing the CNTs is also effective at expelling excess water from the catalyst layer. This allows the maximum pore diameter to be decreased to 5 μm without reducing the ability to prevent flooding, resulting in a much higher performance under high humidity conditions compared with that for a hydrophobic MPL coated GDL.
Measurements of Permeability and Effective in-Plane Gas Diffusivity of Gas Diffusion Media Under Compression
Authors: Mangal Prafful , Dumontier Mark , Carrigy Nicholas , Secanell Marc
Published: September 2014

A novel experimental setup, based on a diffusion bridge, is proposed to accurately and simultaneously measure the in-plane permeability and effective molecular diffusivity of gas diffusion layers used in PEMFC under compression. The permeability is measuredby introducing nitrogen in one channel, forcing the gas through theporous media, and measuring pressure drop at various flow rates. To measure effective diffusivity, nitrogen and oxygen are introduced in two channels separated by a porous media. The flow rate of the gases are controlled by two mass flow controllers. The absolute pressure of nitrogen in the channel is controlled by a back pressure controller. The ratio of convection and diffusion flux is modified by controlling the pressure difference between the gases using a differential pressure controller, connected to the oxygen channel. The oxygen mole fraction in the nitrogen channel is meaured at various differential pressures. A steady state one dimensional Fick - Darcy model is used to estimate the permeability and effective molecular diffusivity based on the experimental data. Toray 090 samples with 0 and 40%PTFE at four compression levels are studied. The permeability and diffusibility (ratio of effective to bulk diffusivity) are found to be between 0.98×10−11 and 0.13×10−11, and, 0.52 and 0.09 respectivelyand are shown to decrease with compression and PTFE.
Effect of through-Plane Polytetrafluoroethylene Distribution in a Gas Diffusion Layer
Authors: Ito Hiroshi , Nakano Akihiro , Iwamura Takuya , Someya Satoshi , Munakata Tetsuo
Published: September 2014

In this study, in order to investigate the effect of polytetrafluoroethylene (PTFE) though-plane distribution on the water discharge characteristic, limiting current measurements were performed under various humidity conditions using a small-scale proton exchange membrane fuel cell (PEMFC). Based on the limiting current measurement, we could evaluate the correlation between the PTFE distribution and the gas transport resistance through the carbon paper GDL.
The Role of Gas Diffusion Layer in Cationic Contamination and Mitigation in Polymer Electrolyte Fuel Cells
Authors: Uddin Md. Aman , Park Jaehyung , Wang Xiaofeng , Qi Jing , Pasaogullari Ugur , Bonville Leonard J. , Molter Trent
Published: September 2014

To understand the role of the gas diffusion layer (GDL) in cation contamination, three methods were used to soak the PEFC MEA with a cationic solution, with the major difference being whether the CCM was completely/partially exposed to the cationic solution or separated by the GDL and gasket. Significant performance drop was observed with the CCMs which were in direct/partially contact with the Ca2+ solution, and no significant change in performance occurred where the CCM was separated by the GDL and gasket. It seems that the GDL acts as a barrier to the transport of Ca+2 into the CCM, possibly due to very highly hydrophobic nature of the GDL. When a surfactant was added to the cationic solution to increase the wettability of the GDL, a drop in the performance was observed which verified that the hydrophobic GDL hindered the transport of Ca2+ into the CCM. When the CCM was reprotonated, the performance was almost fully recovered.
Investigating Inlet Condition Effects on PEMFC GDL Liquid Water Transport through Pore Network Modeling
Authors: Fazeli Mohammadreza , Hinebaugh James , Bazylak Aimy
Published: September 2014

In this work, the influence of the liquid water inlet boundary conditions at the GDL/catalyst layer interface on the spatial distribution of liquid water within the GDL was studied. We used pore network modeling with invasion percolation to simulate liquid water transport in a commercially available GDL, where the detailed, 3D microstructure of the GDL was obtained through X-ray imaging. Three inlet boundary conditions were studied: uniform pressure (single reservoir), uniform flux (completely discretized reservoirs), and distributed uniform pressure (random spatial- and size-distributions of reservoirs). We presented the distributed uniform pressure boundary condition as a more realistic inlet, where inlets are randomly distributed reservoirs that are connected to multiple inlet pores. It was found that the overall saturation ranged from 13% to 23% when the number of inlets ranged from 20 to 300; however, the microporous layer/catalyst layer delamination dominated water transport behaviour.
Effect of the Inlet Gas Humidification on PEMFC Behavior and Current Density Distribution
Authors: Sanchez Daniel G , Ruiu Tiziana , Biswas Indro , Friedrich K. Andreas , Sanchez-Monreal Juan , Vera Marcos
Published: September 2014

Water management represents one of the main challenges in the design and operation of PEMFCs. The influence of inlet gas humidification on cell performance is analyzed using in-situ diagnostic tools, such as cyclic voltammetry and segmented cell current density measurements, supported by post-mortem ex-situ investigations. Particular attention is paid to the effect of low humidity conditions in both cathode and anode, under which the cell is observed to suffer severe voltage decline. A simple one-dimensional water balance model is proposed to contribute to the understanding of the various operation regimes observed in PEMFCs under medium-to-low humidification conditions.
OpenFCST: An Open-Source Mathematical Modelling Software for Polymer Electrolyte Fuel Cells
Authors: Secanell Marc , Putz Andreas , Wardlaw Phillip , Zingan Valentin , Bhaiya Madhur , Moore Michael , Zhou Jie , Balen Chad , Domican Kailyn
Published: September 2014

OpenFCST (open-source fuel cell simulation toolbox) is an open-source, finite element method based, multi-dimensional mathematical modeling software for polymer electrolyte fuel cells. The aim of the software is to develop a platform for collaborative development of fuel cell mathematical models. The philosophy, structure and main components of openFCST are presented. OpenFCST currently includes physical models for gas, electron, ion, ionomer-bound water and heat transport. It also contains effective transport media relations to estimate transport properties for gas diffusion layers, micro-porous layers and catalyst layers as well as several kinetic models for the fuel cell electrochemical reactions. OpenFCST has been structured as a toolbox such that it is easier for new users to integrate new physical models with existing framework. OpenFCST is used to analyze the impact of different kinetic models on a multidimensional cathode model and to study the main differences between a macro-homogeneous and several agglomerate models. Finally, openFCST is used to develop a three-dimensional model of a patterned catalyst layer. Results show that multi-step kinetic models improve fuel cell performance predictions, macro-homogeneous and ionomer-filled agglomerate models show similar performance for 100 nm radii agglomerates up to current densities of 2 A/cm2, and water-filled agglomerate models require negative surface charges to exist at the pore walls in order to provide results in-line with experimental data. Finally, a patterned catalyst layer with micro-pores is shown to improve electrode performance.
The Effect of Cathode Pressure Perturbations on the Voltage Stability of a Simulated Fuel Cell Stack
Authors: Burkholder Michael , Litster Shawn
Published: September 2014

Current strategies for mitigating power loss due to cathode flooding in polymer electrolyte fuel cells are aimed at avoiding the unstable two-phase slug flow regime in the air delivery microchannels by delivering parasitically expensive excessive air flow rates. In this work, we investigate ways to stabilize the slug flow regime and recover voltage by applying low cost cathode pressure perturbations. We experimentally investigate the voltage response to the magnitude and frequency of pressure perturbations applied to a simulated fuel cell stack. The results are applicable to active fuel cell water management.
Numerical Analysis of Proton Conductivity in Hydrated Nafion Membrane Contaminated with Iron Ion
Authors: Kawai Kiyoto , Mabuchi Takuya , Tokumasu Takashi
Published: September 2014

We performed a numerical analysis of the influences of contaminated metal ion on the dynamic properties of proton in a polymer electrolyte membrane (PEM). It was revealed that the nanostructure of the PEM was changed greatly with increasing the concentration of ferric ions. The diffusion coefficient of hydronium ions increases larger at higher water contents with increasing the concentration of ferric ions because of the lower concentration of cations. At higher water contents, the hydronium diffusion coefficient increases largely because ferric ions reduce the electrostatic interactions between hydronium ions and sulfonate groups. At lower water contents, by contrast, the structures between ferric ions and sulfonate groups hinder the hydronium motions resulting in a small increase in the hydronium diffusion coefficient.
High-Resolution Mapping of the PFSA Polymer Distribution in PEFC Electrode Layers
Authors: Koestner Roland John , Cullen David A , Kukreja Ratandeep , Minko Sergiy , Meyer Harry M , Liu Zhongyi , More Karren L.
Published: September 2014

Perfluorosulfonic acid (PFSA) ionomer is a key component within electrode layers for the polymer electrolyte fuel cell (PEFC) since the solid electrolyte enables proton transport to the active catalyst site. Both the through-layer loading on a 100-nm length scale as well as the local film thickness distribution on a 1-nm scale of the ionomer in the porous layer structure are important to electrode performance so quantitative measurements of both properties are desired. In this paper, we present ionomer mapping measurements at both length scales using two common PEFC electrode constructions.
(Invited) Micro Fuel Cells: Can We Apply Them to a Successful Market?
Authors: Esquivel Juan Pablo , Del Campo Francisco Javier , Gomez de la Fuente Jose Luis , Rojas Sergio , Sabate Neus
Published: September 2014

Micro and small size fuel cells have been struggling to find a place in the portable electronics market for decades. Despite their promising capabilities, they have failed to oust lithium-ion batteries as the preferred power source in consumer products. Batteries have successfully evolved into tiny packages that are very easy to use, rechargeable and that can meet the power demands of current portable devices. In contrast, fuel cells still need to overcome cost and system complexity challenges that hinder their widespread adoption. This paper reviews the current attempts in the portable fuel cell area and identifies new trends and opportunities for fuel cells to succeed.
(Invited) Coatings for Robust Metal Bipolar Plates
Authors: Wang Conghua , Tao Yong
Published: September 2014

Metal bipolar plates have the advantage of lighter weight and smaller volume over graphite based bipolar plates for automobile PEM fuel cell stacks. Stainless steel has been identified as the primary candidate of the substrate material. It has reasonable corrosion resistance, high electrical and thermal conductivities, suitable mechanical properties, but still needs certain surface coating to reduce surface electrical contact resistance and minimize metal ions leached from stainless steel substrate for long term durable operation of PEM fuel cell stacks. Various coating technologies have been investigated to protect stainless steel for PEM fuel cell applications. The coatings using precious metals have the advantage of reliable long term durability because of the exceptional stability of precious metals. The focus of this type of coating is to reduce precious metal usage on metal plate surface. One way to reduce precious metal usage is to deposit precious metal in the form of small dots that only cover a small portion of metal plate surface. It can effective reduce the cost of metal bipolar plate and meet the application requirement for PEM fuel cells.
Laser Sealing Technique for Fuel Cell Application
Authors: Lin Chih-Chia , Wang Wen-Lin , Shie Ho-yan
Published: September 2014

Parameter analysis for laser welding, optical measurement tests and tension shear tests are conducted on materials for fuel cell stack bipolar plates, and seven groups of welding parameters are chosen and tested. The optical measurement tests reveal that at the same power and duration time, specimens 1 (20 PPR, 5 mm/s) and 4 (50 PPR, 10 mm/s) obtained greater welding quality with proper welding frequency and velocity. The tension shear tests demonstrate that the bonding strength of both specimen 1 and 4 exceeded 0.4 MPa, the result of which are proper applied to high power fuel cell systems. A new fuel cell stack structure is subsequently designed for this high strength and accuracy modular sealing technique.
Performance of the High Temperature PEM Membrane Electrode Assembly
Authors: Kerr Robert , García Héctor R. , Romero Maria T. , Terkelsen Carina , Hjuler Hans A. , Steenberg Thomas
Published: September 2014

This communication will provide details on some of the high temperature polymer electrolyte membrane (HT-PEM) membrane-electrode-assembly (MEA) performance targets most recently achieved by Danish Power Systems. These include (i) MEA performances of >0.67 V at 0.2 A cm-2 using dry H2/Air, (ii) MEA lifetime of 12000 h at 0.23 A cm-2 using dry H2/Air with an average degradation rate of 9 µV h-1, and (iii) an integrated 5 kW stack/reformer system using methanol reformate as fuel. Studies using reformate have also led to promising results with an MEA performance of 0.58 V at 0.4 A cm-2 with a degradation rate of 24 µV h-1 using wet H2 (30 mol%)/Air for 500 hours. In addition to reaching these performance benchmarks, a reduction in the standard deviation for MEA performance to <5% has been achieved through efforts aimed at improving the uniformity of the membrane and catalyst layer thicknesses.
Development of Anodic Materials with Elevated Hydrogen Sulfide Tolerance for HT-PEMFCs Using Reformat
Authors: Rau Maria , Cremers Carsten , Pinkwart Karsten , Tübke Jens
Published: September 2014

The use of PEMFCs at low or high temperature represents a promising alternative to combustion engines for numerous applications, even if pure hydrogen is not an option as fuel. Unfortunately the presence of C-species and in particular S-species can lead to significant deactivation of the active materials used as electrodes. This is observed as a loss in the performance of the fuel cell. In order to diminish this problem the development of alternatives Pt-based electrodes has been extensively studied. This study presents the development and evaluation of alternative Pt-based electrodes which exhibit a significantly increased resilience against H2S poisoning.
Understanding Direct Borohydride – Hydrogen Peroxide Fuel Cell Performance with a Calibrated Numerical Model
Authors: Stroman Richard O'Neil , Jackson Gregory S.
Published: September 2014

A numerical model is developed for a hydrogen peroxide – direct borohydride fuel cell (H2O2-DBFC) to provide insight into cell processes which are obscured in experiments by the complexity of electrode reactions and transport in the reactant flow channels. In the model, transport is modeled using a 2D finite volume approach. Multi-step electrode reactions, including competing parasitic reactions, are represented by global rate expressions, with parameters calibrated to single-cell experiments. The results are calibrated to a H2O2-DBFC in which fuel (1-50 mM NaBH4 / 2 M NaOH) is oxidized at a Au anode and oxidizer (10-40 mM H2O2 / 1 M H2SO4) is reduced at a Pd:Ir cathode. This modeling approach provides critical insight into the rate-limiting processes at different operating conditions of a H2O2-DBFC.
(Invited) Electrochemical Hydrogen Compression
Authors: Bouwman Peter Jaime , Konink Jonne , Semerel Daniel , Raymakers Leonard , Koeman Menno , Kout Wiebrand , Dalhuijsen Wouter , Milacic Evan , Mulder Martijn J.J.
Published: September 2014

Electrochemical Hydrogen Compression presents solutions to realizing a hydrogen infrastructure and thus providing a sustainable energy network. This technology enables typical bottlenecks of purification and compression to be surpassed simultaneously, but functions only for hydrogen gas specifically. HyET has developed a membrane for electrochemical hydrogen compression showing superior proton conductivity in combination with minimal hydrogen back-diffusion characteristics, to be able to compress to pressures as high as 100 MPa with a competitive energy requirement.
Foam Based Gas Diffusion Electrodes for Reversible Alkaline Electrolysis Cells
Authors: Allebrod Frank , Chatzichristodoulou Christodoulos , Mogensen Mogens Bjerg
Published: September 2014

Alkaline electrolysis cells operated at 250 °C and 40 bar have shown to be able to convert electrical energy into hydrogen at very high efficiencies and power densities. Foam based gas diffusion electrodes and an immobilized electrolyte allow for reversible operation as electrolysis cell or fuel cell. In the present work we demonstrate the application of hydrophobic, porous, and electro-catalytically active gas diffusion electrodes. PTFE particles and silver nanowires as electro-catalysts were used in the gas diffusion electrodes. Impedance spectroscopy and cyclic voltammetry were performed to determine the cell characteristics. The thickness of the electrolyte matrix was only 200 µm, thereby achieving a serial resistance and area specific resistance of 60 mΩ cm2 and 150 mΩ cm2, respectively, at 200 °C and 20 bar. A new production method was developed to increase the cell size from lab scale (1 cm2) to areas like 25 cm2.
(Invited) Comparative Study of the Electrocatalytic Oxidation of Glycerol on Pd-Au/CMO and Pd-Au/MWCNT Nanocatalysts Prepared by the Polyol Method in Alkaline Media
Authors: Arenas-Carmona Rosita , Morales-Acosta Diana , Martinez-Luevanos Antonia , Rodriguez-Varela F.J.
Published: September 2014

In this work, the influence of two carbon supports on the electrocatalytic performance of Pd-Au materials for the glycerol oxidation reaction in KOH electrolyte is investigated. Pd-Au/OMC and Pd-Au/MWCNT have been synthesized by the polyol reduction method. The catalysts have been characterized by XRD, EDS and electrochemical techniques. The results show the influence of the carbon support on the catalytic activity of the Pd-Au anodes. Such effect could be attributed to the fact that the relatively large pores in the OMC support facilitate the mass transfer process, allowing a high concentration of exposed active sites that participate in the reaction.
(Invited) Hydrogen Oxidation and Evolution Reaction (HOR/HER) on Pt Electrodes in Acid vs. Alkaline Electrolytes: Mechanism, Activity and Particle Size Effects
Authors: Durst Julien , Simon Christoph , Siebel Armin , Rheinländer Philipp Jan , Schuler Tobias , Hanzlik Marianne , Herranz Juan , Hasché Frédéric , Gasteiger Hubert A.
Published: September 2014

In this study, we provide an overview regarding our recent finding on the mechanism, activity and particle size effect for the hydrogen oxidation and evolution reaction (HOR/HER) on Pt-group metal electrodes, under both acid and alkaline conditions. We show that there is an activity decrease of about two orders of magnitude when going from acid to base conditions on electrodes which are able to form a H-UPD layer like Pt, Ir, Pd and Rh. Similarities in the HOR/HER process between acid and base conditions have been found: the rate determining step, which has been identified by means of electrochemical impedance spectroscopy measurements to be the Volmer reaction, remains the same and there is no particle size dependency on the reactivity of Pt electrodes. In the light of these finding, Volcano plots of the HOR/HER activities in acid and base have been proposed.
Investigation of Nickel-Rare Earth Electrodes for Sodium Borohydride Electrooxidation
Authors: Santos Diogo M.F. , Sljukic Biljana , Amaral Luis , Sequeira Cesar A.C. , Macciò Daniele , Saccone Adriana
Published: September 2014

Nickel-dysprosium (Ni-Dy) and nickel-samarium (Ni-Sm) alloys were prepared and their morphology, composition and microstructure was analyzed using SEM/EDS and XRD. The alloys were used for fabrication of solid electrodes that were subsequently investigated for borohydride oxidation reaction in alkaline media using cyclic voltammetry, chronoamperometry and chronopotentiometry.
Gold-Zinc-Cobalt Deposited on Titanium as Electrocatalysts for Borohydride Oxidation
Authors: Balčiūnaitė Aldona , Lichušina Svetlana , Šimkūnaitė Dijana , Zabielaitė Ausrine , Selskis Algirdas , Tamašauskaitė-Tamašiūnaitė Loreta , Norkus Eugenijus
Published: September 2014

This work presents the investigation of the electrochemical oxidation of borohydride in alkaline solutions on the ZnCo alloy deposited on the titanium surface and modified with gold nanoparticles (denoted as AuZnCo/Ti). The ZnCo alloy coatings with the thickness of ~5 mm were deposited on the titanium surface (1 x1 cm) via electrodeposition. Au crystallites were deposited on the ZnCo/Ti surface via the galvanic displacement technique. The morphology, structure and composition of the prepared catalysts were examined by Field Emission Scanning Electron Microscopy, Energy Dispersive X-ray Analysis and Inductively Coupled Plasma Optical Emission Spectroscopy. Electrocatalytic activity of the prepared catalysts was investigated towards the oxidation of borohydride by means of cyclic voltammetry, chronoamperometry and chronopotentiometry. It was found that the AuZnCo/Ti catalysts with the Au loadings of 31, 63 and 306 µg cm-2 show enhanced catalytic activity towards electro-oxidation of BH4
– ions as compared to that of ZnCo/Ti, Zn/Ti or Co/Ti catalysts.
Pd-Based Bimetallic and Trimetallic Catalyst for Direct Formic Acid Fuel Cells
Authors: Hu Shuozhen , Noborikawa Jennifer , Haan John , Scudiero Louis , Ha Su
Published: September 2014

The annealing process effect on the activity of Pd/C, PdCu/C alloy, PdNi/C alloy, and the physical mixture of PdCu/C and PdNi/C alloys are studied. These Pd-based bimetallic catalysts are synthesized via a metal-salt reduction reaction. CV results indicate that the non-annealed Pd-based catalysts show similar surface structure and less electrochemical activity towards formic acid oxidation than the annealed samples in the following order: Pd/C < PdNi/C < physical mixture < PdCu/C, After annealing, the PdCu/C shows a surface structure change with more Pd(100) on the surface, while the physical mixture shows not only slightly more Pd (100) but also a larger Hdes peak shift indicative of a weaker Pd-adsorbate bond. Consequently, an enhanced activity towards formic acid oxidation is achieved for both annealed PdCu/C alloy and annealed physical mixture nanoparticles with the physical mixture nanoparticles showing the highest activity (i.e. increased from 1.7 to 3.2 mA/cm2 for PdCu/C alloy and from 1.2 to 3.8 mA/cm2 for the physical mixture nanoparticles). Based on our experimental results, the enhanced activity of the annealed samples is due to the combined effects of structural change and weakening of Pd-adsorbate bond.
Improvement of Ethanol Catalytic Activity by Mn Doped Pt and Pt-Sn/C- Based Catalysts
Authors: Almeida Thiago Santos , Garbin Caique , Palma Livia Martins , De Andrade Adalgisa Rodrigues
Published: September 2014

Because pure platinum is not stable enough for long-term fuel cell operation, researches have been devoted to the development of efficient catalysts for ethanol electrooxidation. To enhance the efficiency of the Pt-based catalysts, a second or third metal is usually added as a co-catalyst. PtSn catalysts are known to be the best composition for ethanol oxidation; however, this composition still requires improvement for application in commercial operational conditions. Therefore, we have introduced manganese and manganese oxides into these catalysts, because they display interesting catalytic properties for the oxidation of small organic molecules, such as excellent proton conductivity, which make them promising co-catalysts or carrier support in fuel cells.
Defective Nitrogen-Doped Graphene Foam: A Non-Precious Electrocatalyst for the Oxygen Reduction Reaction in Alkaline Medium
Authors: Liu Jianfeng , Sasaki Kazunari , Lyth Stephen Matthew
Published: September 2014

The oxygen reduction reaction has faster kinetics in anion exchange membrane fuel cell, opening the possibility of using non-precious materials as electrocatalysts. Therefore, defective nitrogen-doped graphene foam is applied as an electrocatalyst in alkaline medium. The large surface area and highly porous structure results in high oxygen reduction reaction activity in rotating ring-disk electrode measurements. During potential cycling tests, the nitrogen-doped graphene foam displayed comparable durability to a Pt/CB catalyst.
Baseline BTMA Degradation as a Standard for Cationic Degradation in AEMFCs
Authors: Sturgeon Matthew R , Macomber Clay S. , Engtrakul Chaiwat , Pivovar Bryan S
Published: September 2014

Alkaline membranes are of high interest as hydroxide conducting polymers in electrochemical devices. Benzyltrimethylammonium (BTMA) has historically been the cation most often employed in anion exchange membranes. Fuel cell literature often compares cation stabilities under alkaline conditions to that of BTMA. However throughout the literature each study employs a different experimental method when determining these stabilities. This variety of methods makes cross comparisons of novel cations difficult if at all possible. Additionally, we have found that several methods reported have inherent flaws in their findings due to the difficulty of performing stability experiments with high base concentrations. Herein we report a reliable, standardized method of determining cation stability under alkaline conditions that mimic those expected under operating conditions of electrochemical devices. During development, several common experimental pitfalls are addressed and avoided. The standardized method has been employed to determine BTMA stabilities at varying concentrations (0.01, 0.1, and 0.5 M BTMA) at 120, 140 and 160 °C in 2 M KOH in H2O, and have found BTMA to be very stable at 80 °C.
Computational Modeling of Degradation of Substituted Benzyltrimethyl Ammonium
Authors: Long Hai , Pivovar Bryan S
Published: September 2014

The stability of cations used in the alkaline exchange membranes has been a major challenge for alkaline membrane fuel cells. In this paper, we investigated the degradation barriers by density functional theory for substituted benzyltrimethyl ammonium (BTMA+) cations. BTMA+ is one of the most commonly used cations for alkaline exchange membranes. We found that substituted cations with electron-donating substituent groups at meta-position of the benzyl ring could result in improved degradation barriers. However, after investigating more than thirty substituted BTMA+ cations with ten different substituent groups, the largest improvement of degradation barriers calculated was only 1.6 kcal/mol. While this may be a meaningful increase in stability for some applications, it suggests that only a modest improvement in stability is possible through substitution of BTMA+.
Systematic Analysis of Cation Stability in Alkaline Exchange Membrane Fuel Cells
Authors: Mohanty Angela D , Bae Chulsung
Published: September 2014

Improving long-term cation stability in alkaline environment is crucial for adopting anion exchange membrane (AEM) fuel cells as a commercially viable technology in clean energy applications. To reliably identify the most stable cation structures, we analyzed the cation stability of various synthetically prepared quaternary ammonium (QA) organic molecules via a simple silver oxide ion exchange reaction. With this method we were able to compare the stability of various structures of QA hydroxide in water without excess alkaline solution or inconsistencies faced in the presence of polymer backbones. By quantitatively comparing cation degradation via NMR, we were able to identify several cation structures with greater stability as compared to the most well-known benzyltrimethylammonium. From this study we concluded that alkyl-substituted cations seem to impart greater stability than benzylic-substituted cations in the presence of hydroxide anion in aqueous solution.
(Max Bredig Award in Molten Salt & Ionic Liquid Chemistry) Molten Salts and Ionic Liquids: Where Have We Been and Where Are We Going? An Electrochemist’s Perspective
Authors: Hussey Charles L.
Published: September 2014

In this presentation, the award recipient will provide a brief historical perspective about the electrochemical applications of molten salts and their ionic liquid progeny. He will also describe his work with previous Bredig Award recipients and with many other long-time collaborators and students in the field of molten salts and ionic liquids.
Quest for Ether-Coordinated Superoxide Ionic Liquids
Authors: Ishikawa Daisuke , Kitada Atsushi , Fukami Kazuhiro , Murase Kuniaki
Published: September 2014

Novel ionic liquids consisting of superoxide anions and monovalent ether complex cations were investigated. As a result, equimolar mixtures of crown ether and potassium superoxide (KO2) were found to be yellowish ionic liquids with melting points near ambient temperature. Use of glymes, i.e. chain ethers, instead of crown ethers, did not give ionic liquids. Raman spectroscopy and magnetization measurements were performed to check the coordination environment of cationic complexes and the presence of superoxide anions, respectively.
Solubility of Transition Metal Halides in Chloroaluminate Melts
Authors: Karpov Vyacheslav V. , Volkovich Vladimir A. , Polovov Ilya B. , Rebrin Oleg I.
Published: September 2014

The results of the investigation of solubility of several transition metal chlorides (NiCl2, CrCl2, MoCl3, FeCl2) in KCl-AlCl3 based melts are presented. The effect of KCl : AlCl3 mole ratio and melt temperature on solubility of studied metal chlorides is considered.
Direct Electroreduction of Indium and Tin Oxides in Molten Salts
Authors: Qin Bo , Cui Peng , Martinéz Ana Maria , Aune Elizabeth Ragnhild , Haarberg Geir Martin
Published: September 2014

Indium is a rare metal. The largest end use for indium is in thin-film coatings as indium oxide combined with 10 percent tin oxide (ITO). However, indium has recycling rates less than 1%. Indium and tin are especially well suited for fused salt electrolysis because of their low melting points. The electrochemical behaviour of indium and tin oxides was studied by cyclic voltammetry (CV) in molten LiCl-KCl. The direct deoxidation of indium and tin oxides were investigated. A new design of direct electrolytic reduction was proposed considering the low melting points of indium and tin.
Electrochemical Behaviour of Dissolved Iron Chloride in KCl+LiCl+NaCl Melt at 550ºC
Authors: Khalaghi Babak , Kvalheim Eirin , Tokushige Manabu , Teng Lidong , Seetharaman Seshadri , Haarberg Geir Martin
Published: September 2014

An electrochemical study of iron was carried out in KCl+LiCl+NaCl melt at 550ºC using a glassy carbon working electrode. Cyclic voltammetry showed that the Fe(II)/Fe(0) electron exchange is a soluble/insoluble reversible process. The diffusion coefficient of Fe(II) was calculated using cyclic voltammetry; 1.4×10-5 cm2 s-1. For the Fe(II)/Fe(III) red/ox reaction, analysis of the voltammograms suggests that the process is not reversible and is coupled with a chemical reaction. The stability of FeCl3 and the effect of equilibrium between FeCl3 and FeCl2 are also briefly discussed.
The High Temperature Operation of Lithium Secondary Batteries with Using Ionic Liquids
Authors: Matsumoto Hajime , Kubota Keigo
Published: September 2014

The charge and discharge of LiFePO4 half-cells using bis(trifluoromethylsulfonyl)amide based onium salts, such as 1- ethyl-3-methylimidazolium, N,N-diethyl-N-methyl-N-(2-methoy- ethyl)ammonium, N-methyl-N-propylpiperidinium, N-methyl-N- propypyrrolidinium, and N,N,N,N-tetraethylammonium were investigated at over 100 °C. The cell containing tetraethylammonium based melt exhibited best cyclability even at over 125 °C. The cell performances also depend on a concentration of lithium salt, the kind of separator and cell holder.
Synthesis and Characterizations of Cobalt Films Electrochemically Deposited from Aqueous and Non-Aqueous Media
Authors: Dushatinski Thomas , Huff Clay , Abdel-Fattah Tarek M
Published: September 2014

In this study, we characterized the surface morphology of a novel cobalt film electro-deposited from non-aqueous ionic liquid (NCoFs). The roughness of NCoFs is greater than that of aqueous deposited cobalt films (ACoFs) as determined by 1-D surface profiling and scanning electron microscope (SEM) analysis. The improved surface morphology and the catalytic properties of cobalt films can be used as electrodes for water splitting reactions and hydrogen generation.
Preparation of Pt Nanoparticle-Adsorbed Carbon Nanotubes Using Room Temperature Ionic Liquid and Their Use as Electrocatalyst for Oxygen Reduction
Authors: Kuwabata Susumu , Yoshii Kazuki , Tsuda Tetsuya , Torimoto Tsukasa
Published: September 2014

Pt nanoparticles dispersed in room temperature ionic liquid (RTIL) can easily be prepared by just conducting metal-sputtering onto RTIL. When the prepared Pt nanoparticles-dispersed RTIL is put on a glassy carbon (GC) plate or mixed with single wall carbon nanotubes (SWCNTs) while being heated, adsorption of Pt nanoparticles on the carbon surfaces is induced. Both resulting Pt nanoparticles-adsorbed GC and SWCNT exhibit distinct electrocatalytic activity toward oxygen reduction reaction.
(Invited) Glass-Glass Direct Bonding
Authors: Kalkowski Gerhard , Risse Stefan , Zeitner Uwe , Fuchs Frank , Eberhardt Ramona , Tünnermann Andreas
Published: September 2014

Glass-glass direct bonding is closely rated to proven processes in Si-Si wafer bonding. We describe plasma-assisted hydrophilic direct bonding of different glass materials for various applications in optical and high precision engineering. Dedicated “zero-expansion” glass has been used in constructive type “sandwich” bonding of stiff platforms and mirrors as required in space or lithography applications. For transmissive optical applications in the visual and near infra-red spectral range, fused silica is the material of choice and the technology of direct bonding allows to join optical surfaces without an interlayer in a perfectly materials adapted manner. Binary gratings were fabricated and successfully encapsulated in this way for pulse shaping in high power laser devices. The corresponding activities at Fraunhofer IOF are presented and results of supportive laser damage and transmission efficiency measurements for optical characterization are outlined.
Contact Behavior among Vertical Aligned Carbon Nanotube Bumps under Compression for Flexible Multilayer Substrates
Authors: Fujino Masahisa , Terasaka Hidenori , Suga Tadatomo
Published: September 2014

The flexible multilayer substrates with vertically aligned Carbon Nanotubes (VACNTs) have been fabricated by using surface activated bonding method. It became clear that, in the fabrication process, the compression of the VACNT bumps have a substantial impact on their properties. As an evaluation and an analysis, the compressed VACNT bumps occurred plastic deformation above certain load. It is considered that the compressed VACNT contacts each other and friction force is created among them. Furthermore, the contact area among VACNTs contributes resistance of VACNT bumps.
Novel Surface Preparation Methods for Covalent and Conductive Bonded Interfaces Fabrication
Authors: Flötgen Christoph , Razek Nasser , Dragoi Viorel , Wimplinger Markus
Published: September 2014

A novel wafer bonding technology, designed to enable covalent and conductive wafer bonding processes at low temperature was developed. Covalent and conductive bonding processes at low temperatures and even room temperature may become key technology in order to fabricate high performance junctions in compound semiconductor integration applications. This work is presenting the first process qualification results obtained for Si wafers. Apart from equipment characterization data, e.g. particle contamination, data presented here include HR-TEM, EDXS and bond strength analysis achieved for Si-Si hydrophobic wafer bonding.
Surface Characterization for and by Semiconductor Wafer Direct Bonding
Authors: Knechtel Roy , Frohn Natalie , Klingner Holger
Published: September 2014

Semiconductor direct wafer bonding is a very attractive process without any additional bonding layer to stack and join wafers, in order to fabricate special substrates, such as SOI or wafers having cavities sealed with thin membranes for special MEMS processes. With plasma activation, low temperature direct wafer bonding becomes also usable for MEMS applications, in which cap wafer bonding is required at the end of the process. While the surface activation processes required for direct bonding are well investigated and understood, the surface roughness of the layers to be bonded seems to be the limiting factor for this bonding technology, especially if chemical mechanical polishing (CMP) processes cannot be used. In this paper a method is introduced to investigate the bondability of the wafer surface in order to improve the surface roughness and the pre-bonding process.
Hermeticity and Reliability of Al-Al Thermocompression Wafer Bonding
Authors: Malik Nisant , Poppe Erik , Schjolberg-Henriksen Kari , Taklo Maaike Margrete Visser , Finstad Terje G
Published: September 2014

Hermeticity and reliability of laminates bonded by Al-Al thermocompression bonding applying different bonding parameters have been investigated. Laminates of diameter 150 mm were realized by bonding a wafer containing membrane structures to wafers with patterned bonding frames. The laminates were bonded applying a bond force of 36 or 60 kN at temperatures ranging from 300 to 400 °C for 15, 30 or 60 minutes. The hermetic properties were estimated by optical measurement of membrane deflection after bonding. Reliability was tested by exposing the laminates to a steady-state life test, a thermal shock test, and a moisture resistance test. Laminates bonded applying a bond force of 60 kN at temperatures of 350 °C or higher resulted in hermetic and reliable bonds. All the dies on the laminates survived steady-state life test and thermal shock test. Leakage was observed in some dies after exposure to moisture resistance test. Measurements of membrane deflection estimated a maximum leak rate below 10-11 mbar×l×s-1 for all tested bonding parameters.
(Invited) Wafer Bonding: An Integration Route for Hybrid III-V/SiGe CMOS on 300mm
Authors: Czornomaz Lukas , Daix Nicolas , Uccelli Emanuele , Djara Vladimir , Caimi Daniele , Rossel Christophe , Sousa Marilyne , Siegwart Heinz , Marchiori Chiara , Hartmann Jean-Michel , Fompeyrine Jean
Published: September 2014

Direct wafer bonding is one of today’s leading technologies for the dense co-integration of co-planar nano-scaled SiGe p-FETs and InGaAs n-FETs for future low power CMOS application. This paper reports on the fabrication of large-scale InGaAs on insulator substrates, addressing the challenges associated with wafer bonding of InGaAs. It then demonstrates that hybrid dual-channel substrates can also be fabricated by direct wafer bonding with stacked ultra-thin high-mobility layers. These hybrid substrates enable the fabrication of InGaAs/SiGe CMOS circuits.
(Invited) Wafer-Bonding for MEMS – Status and Trends
Authors: Hausner Ralf
Published: September 2014

The current sensor portfolio at Bosch is covering a large variety of different MEMS-based sensor products for automotive and consumer applications. Most of them use wafer-bonding as capping-technology on wafer-level. The basic features that wafer bonding technologies for MEMS must fulfil for a successful wafer-level packaging process are hermeticity, high bond strength and high temperature stability. Glass-frit and anodic bonding are well and long-term established standard technologies used for hermetic packaging of MEMS on wafer-level. But both technologies require comparatively large chip sizes that are not compatible with the requirements for miniaturization and cost reduction of new consumer sensors. Therefore metallic bonding processes like eutectic bonding with aluminium-germanium were used for current sensor generations. One step further is the realization of hermetic encapsulation and electrical interconnection, if an ASIC wafer serves as a functionalized cap. Cu-Cu thermo-compression and Cu/Sn SLID bonding are promising techniques that are of high interest for MEMS products of the future.
Impact Factors on Low Temperature Cu-Cu Wafer Bonding
Authors: Rebhan Bernhard , Wimplinger Markus , Hingerl Kurt
Published: September 2014

Physical mechanism of Cu-Cu wafer bonding was studied as a base for low temperature (<200°C) wafer bonding process optimization. It was found out that for the successful bonding of two copper surfaces the following (classes of) impact factors have to be considered (I) contacting, even at atomic scale, (II) cleanliness of the surface, (III) diffusion enhancing materials properties and (IV) process conditions. From these fundamental findings subsequently low temperature metal thermo-compression Cu-Cu wafer bonding and even room temperature direct bonding was facilitated.
Three-Dimensional Integration of Fully Depleted Silicon-on-Insulator Transistor Substrates for CMOS Image Sensors Using Au/SiO2 Hybrid Bonding and XeF2 Etching
Authors: Hagiwara Kei , Goto Masahide , Iguchi Yoshinori , Ohtake Hiroshi , Saraya Takuya , Toshiyoshi Hiroshi , Higurashi Eiji , Hiramoto Toshiro
Published: September 2014

We have investigated a pixel-parallel signal processing CMOS image sensor for future TV broadcast equipment. The device has a three-dimensional structure containing functional layers made up of components such as photodiodes and signal processors formed on fully depleted silicon-on-insulator transistor substrates connected with vertical interconnections formed for each pixel. To demonstrate the effectiveness of this approach, a test chip is experimentally constructed using Au/SiO2 hybrid bonding technology. Mechanical grinding and XeF2 etching are utilized to remove the backside Si layer to allow light transmission to the photodiode. Due to the high bonding strength after the surface activation treatment, the Si layer thickness could be reduced to 40 µm without chipping. The proposed approach is highly promising for the fabrication of three-dimensional integrated image sensors.