bluuebunny/crossref_metadata_2025_split huggingface dataset:
Durability
Authors: Fujita Y. 
Published: December 2010

AbstractThis paper considers the dominant factors of performance decay of molten carbonate fuel cell (MCFC) stacks. Single cell operation results and the post‐test analysis are discussed, and recent approaches to achieve lower decay rates and longer operation times are described. The decay rate of 1 m2class stacks is analyzed based on single cell data. The life‐limiting factors and the analysis of the decay rate are discussed based on results of stacks with conventional components, which are Ni/Al oxide dispersed strengthen anodes, in situ oxidized NiO cathodes, γ‐LiAlO2matrices with (Li0.62.K0.38)2CO3electrolyte and AISI316L multiple cathode current collectors (perforated plate + corrugated plate). To achieve 40 000 h operation, there were three dominant factors controlling the life and the decay. These factors were the electrolyte loss, the Ni dissolution and the particle growth of LiAlO2. The reduction of the metallic surface area of the cathode current collectors, (Li/Na)2CO3electrolyte and the α‐LiAlO2particles with uniform diameter distribution were examples of the countermeasures and showed good prospects for extending the life of MCFC.
Current electrolytes and catalysts
Authors: Kawada T. , Mizusaki J. 
Published: December 2010

Abstract

Stabilized zirconia (ZrO
2
) is recognized as the major candidate for the electrolyte material of solid oxide fuel cells (SOFCs) owing to its high ionic conductivity and chemical stability. The ionic conductivity originates from the oxygen vacancies introduced by doping 2+ or 3+ valence cations on the Zr
4+
site. The conductivity shows the maximum at a certain dopant concentration. Although stabilized zirconia is a dominantly ionic conductor, electronic conductivity is not completely zero. Taking into account both the ionic and the electronic conductivities, the optimum electrolyte thickness is calculated to be 10–100 µm when the current density of 0.1–1 A cm
−2
is generated at 1000 °C.

Electrode materials should have high catalytic activity, high electronic conductivity, and high chemical and morphological stability. Currently, (La,Sr)MnO
3
and Ni–YSZ cermet are the most popular cathode and anode, respectively. The crystal lattice of (La,Sr)MnO
3
has a distorted perovskite type structure. The symmetry varies with oxygen partial pressure and temperature. Electrical conductivity of La

1−
x

Sr

x

MnO
3
(x = 0–0.4) ranges from 100 to 300 S cm
−1
at 1000 °C in air. Oxygen diffusion coefficient is 10
−12
cm
2
s
−1
, which is not enough to supply oxygen via the electrode bulk diffusion. Although catalytic activity is lower than a mixed conductor oxides such as (La,Sr)CoO
3
, (La,Sr)MnO
3
has higher compatibility with YSZ electrolyte. Nickel is a superior catalyst for the electrochemical and chemical reactions when hydrogen or hydrocarbon gases are used as the fuel. The problem with the nickel anode is its morphological instability and thermal expansion mismatch with YSZ. Thus, nickel powders are used in a form of Ni–YSZ cermet. Electrical conductivity of the cermet electrode varies drastically around the percolation threshold. The optimum nickel content is around 40 vol%.

Electrode reaction kinetics has been investigated intensively for the cathode and the anode. The major origin of the electrode overvoltage is assumed to be the shift of oxygen potential at the electrode/electrolyte contact, which is caused by the formation of oxygen potential gap or gradient to promote the rate limiting reactions. The current–voltage relationship and the electrochemical impedances are well explained under the assumption, and the reaction models were developed by the reaction order analyses.
MEA/cell preparation methods:Europe/USA
Authors: Stöver D. , Buchkremer H. P. , Huijsmans J. P. P. 
Published: December 2010

AbstractCell processing is a key element to providing technical quality and moreover limiting the cost of manufacturing. The processing of cells for solid oxide fuel cells (SOFCs) mostly involves powder technology using suitable methods for the production of bulk as well as layer structured components. The different existing cell concepts and designs are briefly introduced, including tubular and planar types. Methods for the manufacture of substrates and those of layer application are distinguished.Main tools for substrate processing are warm pressing, extrusion and tape casting. These methods are most commonly used to manufacture tubes (by extrusion) as well as plates or foils; possibly by use of all three methods.A variety of coating methods is available and applied to build up the different multilayers necessary to make a fuel cell operational. Wet powder spraying is a flexible wet chemical suspension method to apply electrodes, electrolytes and contact layers. It requires the post treatment of sintering. Vacuum slip casting is a very similar method using suspension pouring on a porous substrate and is used for anode and electrolyte deposition. Electrochemical vapor deposition is used for the production of highly dense electrolytes ready for use without any post treatment, however low deposition rates and high temperatures are drawbacks for mass production. The established technique for plasma spraying is also discussed to some detail. However gas tightness for thin electrolytes and coatings on edges might still be a problem. Screen‐printing is also well established in applying ceramic layers on supporting substrates. Electrodes have been produced in various laboratories. Calendaring has been considered, especially as a lamination route to producing complete cells.Most of the methods need post heat treatments and in order to address the problem of cost reduction, co‐firing steps should be considered. This causes problems of bending and stresses which have to be considered carefully. The chapter closes with some cost considerations of the processes involved.
Interconnects
Authors: Hilpert K. , Quadakkers W. J. , Singheiser L. 
Published: December 2010

AbstractThe interconnect connects the anode side of one single cell with the cathode side of the adjacent single cell, thus preventing the fuel and oxidant gasses from mixing. Ceramic and metallic interconnects are the most widely used concepts. The ceramic interconnect materials used are LaCrO3base perovskites doped with Sr, Ca, or Mg and other metals in order to obtain sufficient electrical conductivity, to modify the thermal expansion, and to improve the sinterability. They are used for tubular cell configurations as well as for the monolithic and planar concepts. Ceramic interconnect materials have shown excellent long‐term behavior for the tubular cells. There is a general trend towards using metallic interconnects in planar cells due to their relatively low costs, easy working potential, as well as high electrical and thermal conductivity. Most developments concentrate on Cr‐based alloys or high‐Cr ferrites depending on the cell design.
Internal reforming
Authors: Eguchi K. 
Published: December 2010

AbstractIn addition to its high conversion efficiency, the solid oxide fuel cell (SOFC) is very attractive from the fuel flexibility point of view. Natural gas has been regarded as the most suitable fuel for the SOFC. Methane, natural gas and hydrocarbons can be readily converted upon direct introduction by a reforming reaction on the Ni/yttria‐stabilized zirconia fuel electrode in the direct internal reforming operation. Internal reforming is attractive not only from the point of view of the simple system, but also the high efficiency due to combined generation with the endothermic reforming reaction. Carbon deposition is one of the damaging factors for the cell for direct internal reforming. The carbon deposition region is determined from thermodynamic equilibrium. Even in the calculated carbon free region, deposition was sometimes observed due to decomposition of hydrocarbon and rapid growth on the Ni catalyst. The selection of the oxide component as well as a metallic component in the cermet should be effective in achieving high performance in the electrode reaction and in avoiding carbon deposition. Stress analysis has been carried out for the internal reforming operation of planar cells. Internal reforming has been successfully carried out in 1 kW planar, several tens of kilowatt scale MOLB type and 10 kW tubular type modules.
System design
Authors: Hartvigsen J. J. , Elangovan S. , Khandkar A. C. 
Published: December 2010

AbstractConceptually, a solid oxide fuel cell (SOFC) is an extremely simple solid state device. Cells, comprised of a thin trilayer of electrochemically functional ceramic materials and operating solely by the passage of electrons, oxygen ions and gaseous reactants, may produce a steady source of electric power. In order to insure efficient and durable operation of such cells, careful control of the chemical reactant and thermal energy flows in the cell environment is required. Design of such systems requires the application of such conventional plant design disciplines as heat transfer, fluid mechanics and catalytic reactor design. The SOFC system offers several opportunities to realize economies of operation and construction by integration of system processes and components beyond those normally implemented in conventional unit operation design. Similarly, showing the effects of system design choices on cell operation gives additional direction to the system design. As there are many means of achieving these design objectives, the approach of various SOFC system developers are considered.
New microtube concepts
Authors: Kendall K. 
Published: December 2010

AbstractMicro‐tubular solid oxide fuel cells (SOFCs) have been developed over the past decade to provide four features which were not thought to be possible in the early 1990s: small SOFC systems from 1 We to 1 kWe; rapid heating systems with start‐up in under 1 min; high power densities near 1 kWe l−1; direct running on a variety of fuels. The main drive for this research emerged as a result of studying extrusion methods for effective fabrication of high quality ceramic membranes, to reveal increased performance combined with extra economy. A further impetus was given by the observation that small tubes of yttria‐stabilized zirconia (YSZ) could resist thermal shocks almost a million times better than flat plate designs. Rapid start‐up of SOFCs thus appeared as a remarkable and new possibility. Such micro‐tubular SOFCs could be used to drive combined heat and power devices to run electronic equipment. Then it became apparent that micro‐tubular cells could run directly on a wide range of fuels, varying from hydrogen, through methane to alcohols to jet fuel and diesel oil. This chapter explains the background and progress of these developments and assesses the potential for further penetration both in technical and application terms.
Direct hydrocarbon
SOFCs
Authors: Barnett S. A. 
Published: December 2010

Abstract

In “direct hydrocarbon” solid oxide fuel cells (SOFCs), the undiluted hydrocarbon fuel is fed directly into the anode compartment, with little or no oxygen‐containing additions (e.g. O
2
, H
2
O, or CO
2
). This can potentially provide the basis for simple, efficient SOFC power plants, and may be an enabling technology for applications such as electricity generation at remote sites, small portable power supplies, and auxiliary power units for vehicles. The main challenge is to develop SOFC anodes that can use hydrocarbons without large overpotentials or carbon deposition. Strategies for electrochemically oxidizing various carbon‐containing fuels without coking are discussed, including reduced operating temperature, alternative anode compositions, and carbon oxidation via electrochemically pumped oxygen. Information currently available regarding the complex reactions of hydrocarbons with typical SOFC anodes is discussed.
Portable
PEM
systems
Authors: Heinzel A. , Hebling C. 
Published: December 2010

Abstract
Fuel cells in the low power range can be operated with either hydrogen or methanol as fuel. Requirements with respect to a hydrogen fuel cell for portable applications are outlined. The state‐of‐the‐art of the development of low power stacks and small‐scale systems is described. Additionally, an overview of the current R&D activities worldwide and of the prototypes presented is summarized, although the reader should be aware of the rapid progress in this type of development. The hydrogen supply to the fuel cell, some properties of hydride materials and data for storage units are considered. The second alternative is to combine the stack with a small‐scale gas processor, and current activities in this sector are described. Finally, a comparison of energy densities of batteries with possible architectures of fuel cell systems is made.
DaimlerChrysler fuel cell activities
Authors: Schmid H.‐P. , Ebner J. 
Published: December 2010

AbstractThis report gives a review of the fuel cell technology used in DaimlerChrysler concept vehicles from 1994 to 2001. The motivation for the strong commitment of DaimlerChrysler in this promising technology is briefly figured out. The basic technical data of all existing fuel cell vehicles of DaimlerChrysler are summarized. Finally, an outlook of ongoing projects, aiming at market preparation is given.
Honda fuel cell activities
Authors: Matsuo S. 
Published: December 2010

Abstract
Honda has demonstrated three types of polymer electrolyte fuel cell systems for vehicles since 1999. The FCX‐V1 was equipped with a metal hydride tank, the V2 with an auto‐thermal methanol reformer, and the V3 and V4 with compressed hydrogen tanks. The FCX‐V3 was introduced to the California Fuel Cell Partnership in Sacramento in November 2000. Operation of the vehicle over a wide variety of city roads and freeways has demonstrated that a fuel cell vehicle is roadworthy and performs capably in traffic. However, there remain areas for further improvements in order to bring fuel cell vehicles into the market.
Market concepts, competing technologies and cost challenges for automotive and stationary applications
Authors: Lipman T. , Sperling D. 
Published: December 2010

AbstractFuel cells have unique attributes that are attractive to automotive and electricity consumers, and also to automotive and electricity companies. These attributes include quiet and responsive operation, high efficiency, low fuel cycle emissions of criteria pollutants and greenhouse gases, and diversity of fuel supply. These features are highly valued in certain market niches and segments, and there are no obvious barriers to fuel cells' entry into the marketplace. Furthermore, three trends serve to reinforce the attractiveness of fuel cells: motor vehicles transitioning from mechanical and hydraulic systems to electrification, electricity generating moving toward distributed generation, and continuing international commitments to reduce greenhouse gas emissions and the environmental footprint of industrial products. However, despite great improvements in fuel cell power density over the past decade, and demonstration of promising performance, both stationary and automotive fuel cell systems face critical remaining challenges. These include primarily cost reduction, achievement of fuel cell system durability targets, development of efficient and low cost fuel reformers, and development of hydrogen storage systems for vehicles that are inexpensive, lightweight, compact, safe, and quick to refuel.
Platinum monolayer oxygen reduction electrocatalysts
Authors: Adzic R. R. , Lima F. H. B. 
Published: December 2010

AbstractIn this chapter, we review briefly the development of a class of highly promising platinum monolayer electrocatalysts that are characterized by a high activity for the oxygen reduction reaction, almost complete platinum utilization, and good long term performance stability. The properties of these electrocatalysts address the major problems of fuel cell electrocatalysis ‐ namely, the insufficient activity of platinum and its excess loading in fuel‐cell electrodes. A detailed analysis of platinum monolayer electrocatalysts is presented including the correlation of their activity with the center of the Pt d‐band, the effects of the types of supports namely, metal, alloy, core‐shell and oxide nanoparticles, and the corresponding mechanistic underpinnings afforded by electronic‐structure theory. In addition, a method of preventing Pt dissolution under certain potential regimes and the behavior of Pd monolayer electrocatalysts are described. Finally, we conclude with an assessment of long‐term fuel cell tests of selected electrocatalysts and their prospects for the future.
Transition metal/polymer catalysts forO2reduction
Authors: Johnston C. M. , Piela P. , Zelenay P. 
Published: December 2010

AbstractTransition metal/polymer catalysts for O2reduction have been investigated extensively as a less expensive, more abundant alternative to platinum catalysts for polymer electrolyte fuel cell (PEFC) cathodes. Embedding metals into polymers offers many potential advantages analogous to the function of metal‐containing enzymes, which include bringing the metal centers into proximity for cooperative action and moderating the local pH near the metal to improve catalyst stability. In this article, we critically summarize the developments in this category of catalysts. While many of the anticipated benefits of the transition metal/polymer catalysts are still to be demonstrated, the most successful aspect of using polymer matrices thus far has been the improved durability. Some newer systems have shown stability for hundreds of hours in the real (acidic) PEFC environment, which was not previously observed for nonprecious catalysts of any type. Although the activity must be increased before any nonprecious metal catalysts are commercially viable, the rich chemistry of polymers allows for many pathways of improvement. We discuss current efforts to understand the structure and action of the active sites and, based on that discussion and research reported to date, suggest future work in the field of oxygen reduction electrocatalysis using transition metal/polymer catalysts.
First‐principles modeling for the electro‐oxidation of small molecules
Authors: Neurock M. 
Published: December 2010

Abstract

The electrocatalytic oxidation of small organic molecules is of great interest in the development of direct liquid fuel cells. While much is known concerning the overall electrocatalytic chemistry, the mechanisms and active sites which control these reactions remain elusive. The advances that have taken place in computation together with new method developments have made theory an invaluable partner with experiment in elucidating the mechanisms and sites that control electrocatalysis. Recent advances in ab initio methods for modeling electrochemical systems and their application to modeling the oxidation of methanol, formic acid and ethanol are discussed herein. The results reveal that while each of these fuels can be oxidized via direct and indirect routes, the controlling paths are function of the molecule as well as the size and configuration of the active surface sites. Methanol proceeds via indirect oxidation paths which require ensemble sizes of at least 3 metal atoms. Formic acid which internally contains CO
2
proceeds instead via a direct path over just 1–2 metal atoms. Ethanol is oxidized primarily to acetaldehyde and acetic acid and requires the presence of defect sites to activate the CC bond. The unique nature of the active site for each of these fuels reveals different alloying effects.
On the pathways of methanol and ethanol oxidation
Authors: Vielstich W. , Paganin V. A. , Alves O. B. , Ciapina E. G. 
Published: December 2010

Abstract

The knowledge on the different oxidation pathways of liquid fuels like methanol and ethanol at Pt‐based electrodes has improved recently. Parallel pathways are responsible for the kind of intermediates, the effective cell voltage, and for the amount of charge per fuel molecule. Both methanol and ethanol have a high thermodynamic energy density, 6000 and 8000 Wh kg
−1
, respectively. In alkaline media, better potential and current density data can be obtained. But the technical application is handicapped by carbonate formation and by a loss of OH
−
electrolyte. Therefore, reactions in acid media are studied and used in fuel cell systems.

This chapter reviews detailed investigations of the pathways of methanol oxidation at different Pt‐metal electrodes. Under optimized operating conditions, an optimum reaction sequence is obtained giving almost 6 e
−
per molecule.

In contrast to CH
3
OH, the two C atoms C
2
H
5
OH shows, at temperatures up to 80 °C, and on PtRu, PtSn, or PtPd as catalysts, less than 4 e
−
per molecule, i.e., at best acetic acid is formed. The main problem in the electrocatalysis of ethanol oxidation is the scission of the C‐C bond, necessary for yielding CO
2
. The detection of intermediates and products and the form of possible parallel pathways are demonstrated. Temperatures around 100 °C and above are problematic for simple fuel cell systems. But under these conditions and using Raney‐Pt catalysts, Sandstede demonstrated in the 1960s that an anodic oxidation of acetic acid is possible.
Effects of contaminants on catalyst activity
Authors: Garzon F. H. , Uribe F. A. 
Published: December 2010

AbstractHydrogen fuel and ambient air contaminants that exhibit strong electrode catalyst chemisorption may severely degrade the performance of polymer membrane fuel cells. Common fuel‐reforming impurities include carbon monoxide and hydrogen sulfide and air impurities include sulfur oxides and nitrogen oxides. CO contamination at parts per million (ppm) levels severely affects fuel cell performance; however, a number of methods including depolarization, air bleeding, and CO tolerant catalyst alloys will mitigate the performance losses. In contrast, the deposition of S on Pt surface from adsorption of sub‐ppm levels of H2S in the H2‐fuel stream results in severe fuel cell performance degradation. The oxidative removal of adsorbed S is a kinetically hindered process and is not achievable at reasonable rates in normal fuel cell operation.
Design rules for the improvement of the performance of hydrocarbon‐based membranes for proton exchange membrane fuel cells (PEMFC)
Authors: Gross M. , Maier G. , Fuller T. , MacKinnon S. , Gittleman C. 
Published: December 2010

AbstractMany different polyelectrolytes have been synthesized over the past decades for application as proton‐conducting membranes in fuel cells. While many of them (polymers as well as membranes) are well studied, it is often hard to identify the specific benefits and drawbacks of one chemical structure over another. On the basis of observations of the effects of certain chemical structures as well as the architecture of the polymer chains on membrane properties such as proton conductivity, water uptake, and durability, this article tries to point out guidelines for the improvement of polyelectrolytes for fuel cell membranes. These guidelines concern polymer properties such as block structures, microphase‐separated morphologies, the type of the attachment of the acidic groups to the polymer chain, the effect of hydrophobicity, and others. The effects of these polymer properties on the behavior of the membrane are described and attempts at explanations for these observations are made.
High‐temperature polybenzimidazol‐based membranes
Authors: Seel D. C. , Benicewicz B. C. , Xiao L. , Schmidt T. J. 
Published: December 2010

AbstractHigh‐temperature polybenzimidazole‐based membranes Polybenzimidazole (PBI) is an excellent material for phosphoric acid‐doped proton exchange membranes. PBI‐based membranes can operate reliably at temperatures above 120 °C, which provides high CO tolerance, fast electrode kinetics, and simplified water and thermal management. PBI membranes prepared by the polyphosphoric acid (PPA) process exhibit improved mechanical properties, proton conductivities, and fuel cell operational characteristics at higher phosphoric acid loading levels compared to the conventionally prepared PBI‐based membranes for high‐temperature fuel cell applications.